SEARCH Workshop on Large-Scale

Atmosphere/Cryosphere Observations

Contribution 2452 from NOAA/Pacific Marine Environmental Laboratory

February 2002

NOAA OAR Special Report

NAT OI NAL OCEANIC AND ATMOSPHERIC ADMINISTRAT OI N

U.S. DEPARTMENT OF CO M MERCE
NOAA OAR Special Report

SEARCH Workshop on Large-Scale

Atmosphere/Cryosphere Observations

Principal Authors:

James Overland

Florence Fetterer

David McGuire

Jackie Richter-Menge

John Walsh

Pacific Marine Environmental Laboratory

7600 Sand Point Way NE

Seattle, WA 98115-6349

February 2002

Contribution 2452 from NOAA/Pacific Marine Environmental Laboratory
NOTICE

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or the tests of such products for publicity or advertising purposes is not authorized.

Contribution No. 2452 from NOAA/Pacific Marine Environmental Laboratory

For sale by the National Technical Information Service, 5285 Port Royal Road

Springfield, VA 22161

ii
Contents iii

Contents

1. Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2. Detection of Arctic Change . . . . . . . . . . . . . . . . . . . 5

2.1 Comparisons of Conceptual Models . . . . . . . . . . . . . . . 5

2.2 Multiple Lines of Evidence . . . . . . . . . . . . . . . . . . . 7

2.3 Impact of Arctic Change on Midlatitude Climate . . . . . . . 8

2.4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3. Atmospheric Observations . . . . . . . . . . . . . . . . . . . . 11

3.1 The Synoptic Observational Network in the Arctic . . . . . . 12

3.2 Satellite Data . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3.3 International Arctic Buoy Programme . . . . . . . . . . . . . 15

3.4 Cloud and Radiation Data Sets . . . . . . . . . . . . . . . . . 16

3.4.1 Existing data sets . . . . . . . . . . . . . . . . . . . 16

3.4.2 Outlook: The next 5 years . . . . . . . . . . . . . . 19

3.5 Satellite Temperature Sounding Data . . . . . . . . . . . . . 20

3.6 Long-Term Intensive Atmospheric Observing Stations . . . . 23

3.6.1 Rationale . . . . . . . . . . . . . . . . . . . . . . . . 23

3.6.2 Strategy . . . . . . . . . . . . . . . . . . . . . . . . 23

3.6.3 The Barrow, Alaska site . . . . . . . . . . . . . . . . 25

3.7 Data Archives . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

3.7.1 Russian radiation data . . . . . . . . . . . . . . . . 27

3.7.2 Arctic hydrology network . . . . . . . . . . . . . . . 28

3.8 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

4. Terrestrial Observations . . . . . . . . . . . . . . . . . . . . . 31

4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

4.2 Key Recommendations for Continuing/Enhancing High Latitude Terrestrial Observations . . . . . . . . . . . . . . . . . . 32

4.3 Opportunities for Continuing and Enhancing High Latitude

Terrestrial Observations . . . . . . . . . . . . . . . . . . . . . 37

4.3.1 Land Cover . . . . . . . . . . . . . . . . . . . . . . . 37

4.3.2 Snow Cover . . . . . . . . . . . . . . . . . . . . . . . 38

4.3.3 Soil Thermal Regime . . . . . . . . . . . . . . . . . 38

4.3.4 Glaciers and Ice Sheets . . . . . . . . . . . . . . . . 38

4.3.5 Lakes and Wetlands . . . . . . . . . . . . . . . . . . 38

4.3.6 Hydrology . . . . . . . . . . . . . . . . . . . . . . . 38

4.3.7 Trace Gas Exchanges . . . . . . . . . . . . . . . . . 39

4.4 Review of Information Presented on High Latitude Terrestrial

Observations—Background on Terrestrial Feedbacks Relevant

to the Arctic System . . . . . . . . . . . . . . . . . . . . . . . 39

4.4.1 Land Cover . . . . . . . . . . . . . . . . . . . . . . . 41

4.4.2 Snow Cover . . . . . . . . . . . . . . . . . . . . . . . 44

4.4.3 Soil Thermal Regime . . . . . . . . . . . . . . . . . 44

4.4.4 Glaciers and Ice Sheets . . . . . . . . . . . . . . . . 47

4.4.5 Lakes and Wetlands . . . . . . . . . . . . . . . . . . 48

4.4.6 Hydrology . . . . . . . . . . . . . . . . . . . . . . . 49

4.4.7 Trace Gas Exchanges . . . . . . . . . . . . . . . . . 51

4.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

5. Sea Ice Observations . . . . . . . . . . . . . . . . . . . . . . . 59

5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
iv Contents

5.2 Recommendations . . . . . . . . . . . . . . . . . . . . . . . . 59

5.3 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

5.4 Key Parameters and Current Measurement Techniques . . . . 62

5.4.1 Ice extent . . . . . . . . . . . . . . . . . . . . . . . . 62

5.4.2 Redistribution . . . . . . . . . . . . . . . . . . . . . 63

5.4.3 Export . . . . . . . . . . . . . . . . . . . . . . . . . 63

5.4.4 Ice thickness and snow depth . . . . . . . . . . . . . 63

5.5 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

6. An Arctic System Reanalysis . . . . . . . . . . . . . . . . . . 69

6.1 Summary and Recommendations . . . . . . . . . . . . . . . . 69

6.2 Presentation and Discussion Issues . . . . . . . . . . . . . . . 70

7. International Coordination . . . . . . . . . . . . . . . . . . . 76

7.1 Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 77

Appendix A: Agenda . . . . . . . . . . . . . . . . . . . . . . . . . . 79

Appendix B: Participants . . . . . . . . . . . . . . . . . . . . . . . 81
SEARCH Workshop on Large-Scale Atmosphere/Cryosphere

Observations

Principal Authors:

James Overland

Florence Fetterer

David McGuire

Jackie Richter-Menge

John Walsh

1. Executive Summary

The Arctic environment has undergone significant temperature swings over

the last 100 years. Over the last 30 years trends show surface temperature

warming, melting permafrost, reduced sea-ice, longer growing seasons, and

changes in the character of tundra. These changes are robust, and many

other biological and physical changes are suggested—redistribution of marine

populations, unusually cold stratospheric temperatures, changes in Icelandic

and Aleutian midlatitude storm tracks, and shifts in ocean circulation. The

Study of Environmental Arctic Change (SEARCH) is based on the principle

that this complex suite of atmospheric, oceanic, and terrestrial changes are

interrelated, with impacts on ecosystems and society.1 It is important to

recognize that these events have already occurred or are under way, and

that it is desirable to anticipate their future course or at least assess their

potential range.

A major task for SEARCH is to determine how existing observation systems can be best used and enhanced to understand and anticipate the course

of the ongoing changes in the Arctic. The purpose of the workshop held in

Seattle during 27–29 November 2001 was to review existing land, sea ice,

and atmospheric observations and the prospect for an Arctic System Reanalysis, through white papers, invited speakers, and panels.2 Assessment

of the equally important areas of paleo-environmental, biological, ocean, and

human observations were beyond the scope of this effort and are the focus

of a future summary. Sixty-eight scientists participated (Appendix B), and

reviews of the areas addressed form the major chapters of this report. Future

efforts across a broad spectrum of disciplines will be accomplished through

the SEARCH Panel on Detection/Observations.

The primary workshop conclusion is that there is no cohesion among

various Arctic disciplines and data types to form a complete observation set

of Arctic change. This situation results from several factors. Many routine observations were not designed specifically for climate studies. Many

research studies are of limited duration at diverse and uncoordinated locations. Temporal intercalibration is lacking between data sets due to changes

1Serreze et al., 2000; SEARCH Science Plan, 2001, http://psc.apl.washington.

edu/search; Unaami website: http://www.unaami.noaa.gov 2Agenda—Appendix A, website http://www.epic.noaa.gov/SEARCH/obs/workshop
2 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

in instrumentation or satellites. In short, there has been no program like

SEARCH to promote and support basin-wide, continuous long-term, multidisciplinary data sets in the Arctic.

A second workshop conclusion is that present data sets are vastly underutilized in understanding Arctic change. Barriers include lack of conceptual

models for conducting interdisciplinary analyses, data accessibility, various

data formats, spatial inhomogeneity, and lack of easily applied tools for visualization and analysis of multi-disciplinary data. SEARCH can provide

solutions by harnessing existing methodologies and technologies.

A third conclusion is that a distributed observing system must accommodate a wide range of spatial patterns of variability. A hypothesis of SEARCH

is that many Arctic processes, both biological and physical, show Arctic-wide

covariability, both for individual variables and between variables. Research

has indicated that even for parameters such as surface temperature, there

is not one fixed mode of variability and that patterns shift on seasonal and

decadal scales. This conclusion leads to the following criteria:  Observations should be pan-Arctic.  Observations should resolve variability on a scale of 500 km, which is

typical of meteorological length scales, or different ecosystems.  Observations should be located in regions of large decadal variability

and long-term trends; priority should be given to locations with long

historical records.  Observations must be multi-variate. Detection and prediction is improved by using multiple indicators.  Data from observations must be accessible. This includes future observations and making available retrospective data sets.

The following bullets provide examples of activities that would address the

first SEARCH workshop conclusion “There is no cohesion among various

disciplines and data types to form a complete observation set of Arctic change”:  Advocate for continued quality-controlled data from surface-based and

satellite weather sensors, permafrost boreholes, glacier and lake monitoring sites, and coordinated runoff measurement activities.  Make the best use of satellite sensing of vegetation changes supported

by continuing selected International Tundra Experiment (ITEX) sites

and IGBP transects.  Develop a climate quality, four-dimensional temperature data set over

the Arctic by upgrading the TOVS soundings by bias removal.  Enhance logistics and sensor suite for the International Arctic Buoy

Program (IABP).  Continue to monitor sea ice extent with microwave sensors from satellite, and use current generation sea ice models and data to design a

system for direct observations to track changes in ice thickness.
SEARCH Large-Scale Observations Workshop 3

Sfc. temperature trend 1950–96 (C/decade)

-0.9 -0.6 -0.3 0 0.3 0.6 0.9

AO surface temperature anomalies (C) 1950–96

-1.5 -1.2 -0.9 -0.6 -0.3 0 0.3 0.6 0.9 1.2 1.5

Figure 1.1: A map of 50-year trends of Northern Hemisphere winter temperatures; (right) the regression

of local temperatures on to the wintertime AO index (JISAO website).  Support the utility of long-term intensive measurement sites, especially radiation and chemistry, at Barrow, Alaska, Kiruna, Sweden,

and Svalbard, with enhanced measurements in northeast Canada and

Siberia.  Initiate summaries of biological, oceanographic, and human observations. Note the existing Paleoenvironmental Arctic Sciences (PARCS)

data archive at http://www.ngdc.noaa.gov/paleo/parcs.  Strengthen international coordination.

The following bullets provide examples of activities that would address the

second workshop conclusion, “Present data are vastly underutilized in understanding Arctic change”:  Initiate a high-resolution Arctic System Reanalysis.  Develop a protocol for detection of Arctic change.  Develop multiple lines of evidence for change and make evidence available at a single website location.  Support gridding and time intercalibration of satellite products for the

Arctic.  Support standards for data sets and metadata to readily permit timely

sharing of information and enhance multidisciplinary analyses.
4 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

As an example of the third workshop conclusion, that “A distributed observing system must accommodate a wide range of spatial patterns of variability,” Fig. 1.1 (left) shows the map of wintertime temperature trends for the

Northern hemisphere for the previous 50 years. There is large-scale spatial

covariability, with warming trends over eastern Siberia and northwestern

North America, and cooling over NE Canada and, to some degree, west of

Bering Strait. To the right is shown the regression of temperatures at each

location onto the Arctic Oscillation (AO), an index of northern hemisphere

atmospheric circulation. The temperature pattern for the AO is similar to

the 50-year trend in NE Canada and eastern Siberia, but there are differences: the AO has a stronger response in Scandinavia, and the cold region

near Bering Strait now extends over Alaska. Eastern and midwest North

America now shows warming. Even for surface temperatures there is not

one fixed mode of variability; indeed these patterns shift on seasonal and

decadal scales (Overland et al., 2002).

1.1 References

Overland, J.E., M. Wang, and N.A. Bond (2002): On the recent temperature

changes in the western Arctic during spring. J. Climate, 15, in press.

SEARCH Science Plan (2001): available at http://psc.apl.washington.edu/

search/

Serreze, M.C., and coauthors (2000): Observational evidence of recent change in

the northern high latitude environment. Clim. Change, 46, 159–207.
SEARCH Large-Scale Observations Workshop 5

2. Detection of Arctic Change

One of the goals of SEARCH is to project the future course of the recent and

ongoing decadal (e.g., 3–50 year), pan-Arctic complex of interrelated changes

in the Arctic. A major suggestion at the workshop was that SEARCH would

be well served by further developing the definition of detection of Arctic

change. Change in the Arctic is multivariate and understanding the interrelation of the parts is a goal of SEARCH. Nevertheless, developing an

operational definition would:

1. Help refine SEARCH hypotheses,

2. Aid in prioritizing an observational system, and

3. Improve communication of SEARCH results.

Therefore, a recommendation of the workshop is:  Develop a protocol for detection of Arctic change.

In review of the literature (Klein, 1990; Risbey et al., 2000) on multidisciplinary projects of large scope, credibility of the process is a major

feature and is enhanced through quality control of the components, reproducibility of the analyses, stating uncertainties, clarity and transparency,

without sacrificing the recognition of the underlying complexity of the system. Such procedures are promoted through formal methods, which develop

alternate quantifiable metrics for specifying historical change and future detection. Because of the existence of different lines of evidence for Arctic

change over the last 30 years, SEARCH is a candidate for a comparative

approach to interdisciplinary studies.

“Detection” as used by SEARCH has a broader context than is used by

the climate change community. For climate change, detection is often used

in a narrow sense that some indicator, such as global surface temperature,

exceeds the range of background noise of natural climate variability (Barnett et al., 1999), i.e., due to anthropogenic and other external factors. For

many ecosystem and societal applications of SEARCH, it is important to

understand the ongoing changes in the Arctic, whether they are natural or

external. Several authors have argued that external change will amplify or

change the frequency of occurrence of natural large-scale patterns of variability (Palmer, 1999); this remains to be shown in the Arctic.

In this section, we do not develop a protocol. This should be an early

activity of the SEARCH panel on detection/observations. We provide three

examples which more fully develop detection concepts: (1) comparison of

conceptual models of Arctic variability, (2) the use of multiple lines of evidence, and (3) selection of robust indicators for the impact of Arctic change

on midlatitude climates.

2.1 Comparisons of Conceptual Models

The mean annual surface temperatures for the northern hemisphere in the

20th century increased until about 1940, slightly decreased until the early
6 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

Year 1850 1900 1950 2000

1.0

0.5

0.0

0.5

1.0

model

observations

Temperature Anomalies C

Stott, et al. 2001

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Ice Anomaly Ice Anomaly

Venegas & Mysak, 2000

0.2

0.1

0.0

-0.1

-0.2

-0.3

1950 1990 1960 1980 1970

Polyakov & Johnson, 2000

0.3

Simulated annual global mean surface

Vorticity Index temperatures with all the forcings

Greenland Sea Greenland Sea

Figure 2.1: Recent trends of Arctic data. The upper left panel shows shifts in an Arctic atmospheric

circulation index, based on vorticity. The lower panel shows changes in Greenland Sea ice anomalies (right)

broken down into four different frequency components (left). The upper right panel shows modeled and

observed global temperature changes over the last century.

1970s, and increased through 2000. Changes in the Arctic mirrored the

northern hemisphere with, perhaps, a greater relative increase in the 1930s.

These temperature changes are reflected in other variables such as the

strength of the polar vortex and ice extent. The upper left panel in Fig. 2.1

from Polyakov and Johnson (2000) shows both a decadal scale variability associated with the Arctic Oscillation (AO) and a 60–80-year Low Frequency

Oscillation (LFO). Because the LFO and AO both have a positive phase in

the 1990s, these authors suggest that a forward projection of these two oscillations would predict a major temperature reversal in 2000–2020; we can

call this the extrapolation model. The Greenland Sea ice record (Fig. 2.1,

bottom right) was decomposed by Venegas and Mysak (2000) into four frequency bands (Fig. 2.1, bottom left). The sum of their low frequency and

decadal oscillations also show a minimum ice area in the 1990s, with a projection for increases after this minimum.

An alternative model comes from the Global Climate Model (GCM) hindcast for the 20th century completed for Intergovernmental Panel on Climate

Change (IPCC) (Scott, 2001). The temperature observational record and

an ensemble average of four model runs is shown in Fig. 2.1 (upper right).

These results show the temperature maximum in the late 1940s; the model

attributes this warming to a weak solar radiation influence plus natural
SEARCH Large-Scale Observations Workshop 7

variability in two of the four ensemble runs. However, the models could not

reproduce the dramatic temperature increase in the 1990s without including

increased CO2 forcing in their model. Thus, the IPCC conceptual model

would project increased warming in 2000–2020, after a brief minimum associated with the decadal change of the AO. One formal approach to detection

is through the comparison of models. In the two examples we have major

differences in these projections for the next 20 years. What is the evidence

for each approach?

A third default model may also be considered. The previous examples

project an ordered systems response. We can also hypothesize a stochastic

or chaos-like system (Rind 1999; Overland, 2000). There is some suggestion that the northern hemisphere atmosphere system has several alternate

states (Corti et al., 1999). These states can have preferred residence times

and long-memory behavior (Percival et al., 2001), but also suggest that the

system can have regime transitions or shock-like behavior. The large interannual variability of the AO during the previous 4 years (1999–2002) could

suggest that the atmosphere is in a transition between more stable states.

While prediction of a system with this type of climate noise is impossible,

understanding the nature of the low frequency variability would help with

the detection of rapid transitions.

2.2 Multiple Lines of Evidence

SEARCH is based on several recent observed changes in the Arctic which are

robust: declines in sea level pressure, increased surface air temperatures, cold

stratospheric temperatures, decreased sea ice cover, permafrost temperature

increases, longer growing seasons, and changes in the character of tundra.

There are many other less robust physical and ecosystem changes that have

occurred over the previous 30 years in the Arctic.

SEARCH can benefit from a more formal compilation of this information

to address the multivariate aspects of Arctic change. An excellent example is

provided by Hare and Mantua (2000) for the North Pacific. In comparing 100

time series, they show that biological time series were the better indicators

of regime-like behavior in 1976 and 1989 than physical data alone. Physical

data has large interannual and multi-scale variability, while the biological

data acted as a filter on the physical system.

The formal approach examines different lines of evidence. One can investigate the sources, quality, and quantity of available data. Uncertainties

can be estimated and the signal/noise issue can be addressed individually.

One can reduce the dimension of the system by the selection of relatively

independent lines of evidence versus those subsets which covary in time or

have similar spatial patterns. The process can be transparent and several

approaches can be taken for detection. For example, the time series can

be combined into a single attribution, with greater confidence than for any

individual variable. Alternatively, each series can be tested separately, and

detection can be based on categories, such as “most” of the evidence, the

“balance” of the evidence, or “some” of the evidence depending on the number of series which pass a given detection criteria.
8 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

http://www.unaami.noaa.gov

Figure 2.2: A sample from a data collection web site for 85 Arctic time series sorted by location and data

type.

Figure 2.2 shows a data collection for the Arctic of 85 time series divided

into seven categories: fisheries, biology, terrestrial, sea ice, ocean, atmosphere, and climate indices (http://www.unaami.noaa.gov). These data

were chosen to span the years 1975–1995. The number of long time series

drops off significantly before this time. Longer time series of a century or

more are available; sea ice extents and air temperatures are an example as

discussed by R. Colony at the workshop. Such expanded data collections

should form the basis of understanding the covariability and independence

of Arctic change.

2.3 Impact of Arctic Change on Midlatitude Climate

At the workshop, Mike Wallace (Thompson et al., 2001) made a presentation which shows an example of research driven by a potential application.

Thompson et al. noted the number of days during winter when 14 cities had

extreme cold temperatures, colder than 1.5 of the standard deviation from

the mean value (Table 2.1). They sorted this data into those days after
SEARCH Large-Scale Observations Workshop 9

Table 2.1: Number of days of cold temperatures which follow a weak vortex (negative AO) versus a strong vortex (positive AO).

Weak vortex: Strong vortex:

–1.5 std. temperature threshold Total days +1–60 days +1–60

< −17◦C in Juneau, AK 334 104 66

< −18◦C in Chicago, IL 411 149 67

< −6◦C in Atlanta, GA 416 149 73

< −10◦C in Washington, D.C. 392 153 77

< −9◦C in New York, NY 403 164 99

< −1◦C in London, UK 442 157 77

< −3◦C in Paris, France 446 148 68

< −9◦C in Stockholm, Sweden 348 154 54

< −9◦C in Berlin, Germany 450 142 77

< −22◦C in St. Petersburg, Russia 381 137 46

< −20◦C in Moscow, Russia 472 152 80

< −29◦C in Novosibirsk, Russia 480 155 69

< −4◦C in Shanghai, China 471 170 84

< −1◦C in Tokyo, Japan 328 130 60

Thompson et al., 2002

the atmosphere shifted to a weak vortex (negative AO) and a strong vortex

(positive AO). The negative phase of the AO has a more north-south wavelike character compared to the positive AO with a more west-east (zonal)

character. The number of cold days associated with a weak vortex were

about double the number associated with the strong vortex. They further

showed that the magnitude of the change was about 3 degrees over northern

midlatitudes, about the same magnitude as the influence of a shift from El

Ni ̃no to La Ni ̃na. Thus, by focusing on extreme events rather than mean

values, these authors demonstrated a practical midlatitude influence of the

AO.

2.4 References

Barnett, T., and coauthors (1999): Detection and attribution of recent climate

change: A status report. Bull. Am. Meteorol. Soc., 80, 2631–2659.

Corti, S., F. Moltieni, and T.N. Palmer (1999): Signature of recent climate changes

in frequencies of natural atmospheric circulation regimes. Nature, 398, 799–802.

Klein, J. (1990): Interdisciplinarity: History, Theory, and Practice. Wayne State

University Press, Detroit, MI, 331 pp.

Overland, J.E., J.M. Adams, and H.O. Mofjeld (2000): Chaos in the North Pacific:

Spatial modes and temporal irregularity. Progress Oceanogr., 47, 337–354.

Percival, D.B., J.E. Overland, and H.O. Mofjeld (2001): Interpretation of North

Pacific variability as a short- and long-memory process. J. Climate, 14, 4545–

4559.

Polyakov, I., and M.A. Johnson (2000): Arctic decadal and interdecadal variability.

Geophys. Res. Lett., 27, 4097–4100.

Rind, D. (1999): Complexity and climate. Science, 284, 105–107.

Risbey, J.S., M. Kandlikar, and D. Karoly (2000): A protocol to articulate and

quantify uncertainties in climate change detection and attribution. Climate

Res., 16, 61–78.
10 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

Stott, P.A., and coauthors (2001): Attribution of twentieth century temperature

change to natural and anthropogenic causes. Climate Dyn., 17, 1–22.

Thompson, D.W.J., M.P. Baldwin, and J.M. Wallace (2002): Stratospheric connection to northern hemisphere wintertime weather: Implications for prediction.

J. Climate, 16, in press.

Venegas, S.A., and L.A. Mysak (2000): Is there a dominant timescale of natural

climate variability in the Arctic? J. Climate, 13, 3412–3434.
SEARCH Large-Scale Observations Workshop 11

3. Atmospheric Observations

Compiled by James Overland with contributions from Roger Colony, Jennifer

Francis, Barry Goodison, Roy Jenne, Jeff Key, Lawrence Mysak, Steven

Pawson, Ignatius Rigor, Bob Stone, Patrick Sheridan, Russ Schnell, Mike

Wallace, Betsy Weatherhead, Taneil Uttal, and Bernie Zak.

A goal of SEARCH is the development of a distributed observing system

to track Arctic change. This observing system includes both biological

and physical data. The backbone is the World Meteorological Organization (WMO) sites, which collect routine weather data, and current and future environmental satellites. This information net is primarily designed for

operational, short-term weather forecasting, rather than long-term climate

studies. The operational focus creates potential problems in using the WMO

data to detect changes over decadal time scales. Issues include data accuracy,

ability to detect small changes, the length and continuity of the record, site

changes and urbanization, and changes in instrumentation type and automation. Arctic scientists share the issue of using WMO and satellite data for climate purposes with the larger climate community. Such issues are addressed

by the Global Climate Observing System (GCOS) at http://www.wmo.ch/

web/gcos/.

As noted in the Introduction, there are changes in the Arctic that show

large-scale (500 km+) covariability, but there is no one particular spatial pattern of variability. Thus, to explore and potentially project such changes, a

uniform distribution of sites is necessary (300–500 km) which track a variety

of processes. SEARCH provides an Arctic component to the overall global

climate program by providing a focus for Arctic observations and parameterization of Arctic processes in climate models. Thus, the recommendations

for atmospheric observations in SEARCH are primarily to augment routine

atmospheric observing systems and for quality control of operational data.

Recommendations  Although the current set of WMO surface observation stations is adequate for SEARCH purposes, we advocate for continuation of quality

measurements, intercomparison of measurements, and support of easily

accessible, current, and archives of value-added data sets. The subset

of GCOS surface network (GSN) stations is not adequate to monitor

the potential spatial variability of Arctic change.  The number of WMO upper air locations is only about 10% of the

number of surface stations; there is no coverage over the central Arctic.

This provides a major data void for SEARCH research. SEARCH

has an opportunity to improve this situation by converting the 22-year

historical TOVS atmospheric temperature sounder data set to climate

quality by bias removal for the Arctic portion of the entire data set.  The International Arctic Buoy Program (IABP) has maintained sea

level pressure observations in the central Arctic since 1979. SEARCH
12 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

can support IABP by providing logistics to keep a uniform grid of observations, and enhancing the sites with additional sensors such as

quality temperatures, radiation, ice thickness, and ocean properties.  SEARCH sees great utility for value-added gridded data sets from satellite data, such as cloud, vegetation, and radiation fields.  Intensive observing sites are located at Barrow and Northern Europe.

Because of the large-scale spatial variability of changes in the Arctic,

it is important to maintain observations at a site in NE Canada with

the same range of observational measurements. Future consideration

should be made for a Siberian site.  Work is required to prioritize integrated data sets for change detection.

3.1 The Synoptic Observational Network in the Arctic

At the workshop, Barry Goodison and Roy Jenne reviewed the meteorological observation network in the Arctic. The number of surface stations

north of 50◦N as of 29 October 2001 was 2477 and are shown in Fig. 3.1.

The source of this metadata is WMO Publication No. 9, Volume A, which

contains a complete list of the active surface and upper air weather observing stations at http://www.wmo.ch/web/ddbs/publicat.html. The publication is updated every 2–3 months. A second source of data is from

the Global Climate Observing System (GGOS) Surface Network (GSN),

http://www.wmo.ch/web/gcos/gcoshome.html. The GSN is a subset of

989 sites for the globe (244 sites north of 50◦N) selected for quality, continuity, and longevity, with a coverage every 500 km. Polyakov et al. (2002)

make use of 49 Arctic stations with data time series longer than 65 years.

Given the large regions of covariability for many variables of Arctic

change as suggested in Fig. 1.1, the WMO Station coverage for temperature and pressure, and the present archiving by the National Climate Data

Center (NCDC), appear adequate for the requirements of SEARCH historical analyses and future detection activities. We can make this statement

even with the loss of some stations in the Russian Arctic. It should be

recognized, however, that good spatial coverage of observation sites are an

essential underpinning of research to improve understanding of the climate

system. SEARCH should be concerned about further loss of observation

sites, especially those with long historical time series, and the continuity

and intercalibration within the records.

The large void over the central Arctic ice pack in Fig. 3.1 is covered

through the International Arctic Buoy Program (IABP). Further details will

be provided in Section 3.3. Another source of weather information is the Arctic Climate System Study (ACSYS), Precipitation Data Archive (APDA),

http://dwd.de/research/gpcc/acsys. As of December 1999, they list

Arctic synoptic weather stations as well as a subset of stations sorted by

river catchment areas. They also link to 30 other snow and precipitation

data sources.
SEARCH Large-Scale Observations Workshop 13

WMO Publication No. 9 Volume A

All active Synoptic Stations north of 50 N as of 29 Oct 2001

90° N

75° N

60° N

45° N

2477

90° N

75° N

60° N

45° N

2477

Figure 3.1: Location of WMO surface observation stations.

The coverage of upper air profiling stations from the WMO web site is

shown in Fig. 3.2. The number of stations is just 10% (238) of the number

of surface stations. The number of stations is particularly low over the high

Arctic (land area) and non-existent over the Arctic Ocean basin. This lack

of coverage is a major problem. One opportunity for upper air data in the

Arctic is through the use of satellite sounder data available since 1980. This

was an operational weather product and needs to be recalibrated as a climate

product. Additional discussion is in Section 3.5.

A method to make the best use of this limited information is through

Reanalysis Projects, such as that undertaken by the NCAR Data Support

Section and the Model Development Group at the National Center for Environmental Prediction (NCEP). The NCAR group has developed an extensive

data set with major quality control, duplicate removal, and systematic error removal. The 110 upper air stations north of 60◦N and their period

of coverage during the period 1940–1999 are listed on the workshop web

site: http://www.epic.noaa.gov/SEARCH/obs/workshop/reports.shtml

under Roy Jenne. This upper air station data, along with surface reports,

aircraft reports, and some satellite wind and temperature data after 1973,

are used in a 6-hour analysis/forecast cycle using a state-of-the-art weather

forecast model to extrapolate the observations in space and time. The extrapolation is good when there is adequate data coverage upwind of the

region of interest. Lack of coverage remains a problem for the central Arctic. The NCAR/NCEP reanalysis has a nominal resolution of 208 km. The
14 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

WMO Publication No. 9 Volume A

All active Upper Air Stations north of 50 N as of 29 Oct 2001

90° N

75° N

60° N

45° N

238

Figure 3.2: Location of WMO upper air observation stations.

model also computes secondary variables which are not measured directly,

such as radiation and moisture fields. Reanalysis fields are available at

http://wesley.wwb.noaa.gov/ncep data/index.html. Thirty-one variables are available on different atmospheric pressure levels and 62 additional

variables at a single pressure level. Further information on the NCAR processed data set is at http://dss.ucar.edu.

3.2 Satellite Data

Satellites provide a spatial and temporal basis for following Arctic change.

A review of satellite and data center issues is provided in a National Research Council (NRC) Report, Enhancing NASA’s Contributions to Polar

Science (J. Walsh and coauthors, 2001). Certainly the Polar Operational

Environmental Satellites with twice daily coverage of visual and IR images

and temperature soundings are basic. MODIS (MODerate resolution Imaging Spectroradiometer) flying on TERRA and to fly on AQUA provides

imaging in 36 spectra bands every 2 days. The future ICESat mission will

provide cloud property information not otherwise available from passive sensors, especially the high ice clouds common over polar areas. It will have an

altimeter to provide information on ice sheets. The Total Ozone Mapping

Spectrometer (TOMS) has provided measurements for most of the period

1978–present.

Key recommendations from the NRC report are:
SEARCH Large-Scale Observations Workshop 15

 Foster consistency within and among different satellite products.  Develop spatially and temporally coherent geophysical data sets.  Provide emphasis to sensor optimization for polar applications, which

is not now a priority. Clear examples are precipitation estimation and

cloud properties.  Data centers should work toward improvement of tools for analyzing

combined data sets. This includes documentation, temporal consistency, gridding, and format conversions.

3.3 International Arctic Buoy Programme

Ignatius Rigor reported that the International Arctic Buoy Programme

(IABP) has maintained a network of buoys in the Arctic Basin since 1979.

These buoys measure sea level pressure (SLP), surface air temperature (SAT),

and other geophysical quantities. The data are transmitted and collected

through the Argos satellite system. The IABP strives to maintain a network

of at least 25 buoys evenly distributed across the Arctic Ocean. These buoys

have expected life spans of 1 to 2 years, and more than 5000 buoy-months

of data from over 500 buoys have been collected.

The IABP data are used for both operations and research, e.g., forecasting weather and ice conditions, validation and forcing of climate models,

validation of satellite data, and for studies of climate change. For operations,

the data are made available to the forecasting community through the Global

Telecommunications System. For research, the data are analyzed at the Polar Science Center of the University of Washington, which also coordinates

the IABP. The data and more information on the IABP can be obtained

from http://IABP.apl.washington.edu/, or from the World Data Center

for Glaciology at the National Snow and Ice Data Center in Colorado.

The success of the IABP depends on maintenance of the buoy network.

The buoys have finite life spans, and a tremendous amount of resources are

required to purchase and deploy buoys. In the past the program was able

to seed the buoy network in the Beaufort Sea and the large gyre circulation

would carry buoys out to cover the Arctic Ocean. However, given the recent

predominance of high AO conditions reducing the Beaufort Gyre, maintaining the buoy array in the east Arctic has been more difficult. Therefore,

an opportunity for SEARCH is to provide increased support for logistics and

continued development of methods for seeding the eastern Arctic. For example, Fig. 3.3 shows a recent location of the buoy array, with a particularly

large data void in the central/eastern Arctic.

Given the complex nature of Arctic climate, another SEARCH opportunity is to develop and deploy buoys with more sensors, e.g., CTDs, anemometers, radiometers, and thermistor strings. The cost to attach additional sensors to a buoy is small in comparison to the cost of the logistics to deploy

a buoy, but the benefits to the operational and research communities can

be significant. These additional data are useful in their own right and are

essential for calibrating radiation and GCM models.
16 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

1222

2159 2416 2419 3311

3692

3693

5300

5311

8056

8063 9357

9359

9360

9432 94309431

9433

943594379436 9434

9439 9438

9440

9492

11257

12791

12793

15524 18921

19577

19579 19578

20857

20858

20859

22206 21077

24289

24291 24292

24294

27414

26996

26998

26999

International Arctic Buoy Program

1 Mar 2002

 Argos Buoys

 Land Stations

500 km.

1 March 2002

Argos Buoys

Land Stations

International Arctic Buoy Programme

IABP Land Stations

Buoys that may have failed since 20020201

Figure 3.3: Locations of buoys as part of the International Arctic Buoy Program (IABP). Note the data

void in the central Arctic.

3.4 Cloud and Radiation Data Sets

Jeff Key reported that both in situ and satellite-derived cloud and radiation

data sets are available for Arctic climate studies. The following list includes

those that can potentially be used for the detection climate change. It does

not include data sets collected during field experiments or data that do not

constitute a time series. The temporal scales range from hourly to monthly

averages, covering periods up to four decades.

3.4.1 Existing data sets

Baseline Surface Radiation Network (in situ): The Baseline Surface

Radiation Network (BSRN) is a project of the World Climate Research Programme with a goal of detecting changes in the earth’s radiation field over

long time scales. BSRN stations in the Arctic are at Barrow, Alaska, and

Spitsbergen, Norway. The Antarctic BSRN stations are Neumayer, Syowa,

and South Pole. All stations measure global, direct, diffuse, and longwave

downward radiation. All but Syowa also measure shortwave and longwave

upward radiation and have 3-hourly synoptic observations. Spitsbergen and
SEARCH Large-Scale Observations Workshop 17

MISSING

RESERVED

800.00

720.00

640.00

560.00

480.00

400.00

320.00

240.00

160.00

80.00

Downwelling SW Flux, Surface

Figure 3.4: Downwelling shortwave flux at the surface for the month of June,

averaged over the period 1985–1993, calculated from the AVHRR Polar Pathfinder

data set.

Neumayer have instrument-measured cloud base height. The stations began measurements as part of the BSRN in 1992 and 1994. On the Web:

http://bsrn.ethz.ch.

Arctic Global Radiation Data Set (in situ): The Arctic Global

Radiation (AGR) data set was compiled from Arctic land stations, ocean

drifting stations, and empirically derived long-term climatological estimates

from earlier Russian studies (Fig. 3.4). The AGR is a two-part data set,

the first being a time series of monthly fluxes covering the region north of

60 degrees latitude. While many of the station time series are short, some

exceed 40 years in length. The second part of the AGR is a long-term

monthly mean gridded climatology for the region north of 65◦N. On the

Web: http://nsidc.org/data/arcss066.html.

Edited Synoptic Cloud Reports Over the Globe (in situ): Surface synoptic weather reports over the globe for the 10-year period from

December 1981 through November 1991 were processed by C. Hahn, S.

Warren, and others to provide a data set designed for use in cloud analyses. The information in these reports relating to clouds, including the

present weather information, was extracted and put through a series of

quality control checks. With this data set a user can develop a climatology for any particular cloud type or group of types, for any geographical region and any spatial and temporal resolution desired. On the Web:

http://cdiac.esd.ornl.gov/epubs/ndp/ndp026b/ndp026b.htm.

AVHRR Polar Pathfinder (satellite): The AVHRR Polar Pathfinder

composites are a collection of products for both poles, consisting of twice-
18 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

Figure 3.5: Locations of data sources in the AGR data set.

daily gridded and calibrated satellite channel data and derived parameters at

a 5 km spatial resolution. Data include five Advanced Very High Resolution

Radiometer (AVHRR) channels, clear sky surface broadband albedo and skin

temperature, viewing and illumination geometries, surface type mask, cloud

mask, and time of acquisition. Data are composited onto two grids per day

based on common local solar times and scan angle. The data set currently

covers the period 1981–1998. The APP data set has been extended to include

cloud properties, surface radiation, and top-of-atmosphere radiation. At

present the years 1982–1993 have been processed. An example is shown

in Fig. 3.5. On the Web: http://nsidc.org/data/nsidc-0066.html and

http://stratus.ssec.wisc.edu/projects/app.

TOVS Path-P (satellite): The TIROS-N Operational Vertical Sounder (TOVS) Polar Pathfinder (Path-P) data set consists of gridded daily

Arctic fields of atmospheric temperature, water vapor, skin surface temperature, total effective cloud fraction, cloud top pressure and temperature,

solar zenith elevation, surface pressure, turning angle between geostrophic

wind and surface stress over ice, emissivity, boundary layer stratification,

and the geostrophic drag coefficient. Data are available for the period 1979–

1998 at a resolution of 100 km. An example is shown in Fig. 3.6. On the

Web: http://nsidc.org/data/nsidc-0027.html.

International Satellite Cloud Climatology Project (satellite):

ISCCP was established as part of the World Climate Research Programme

to collect and analyze satellite radiance measurements to infer the global

distribution of clouds, their properties, and their diurnal, seasonal, and in-
SEARCH Large-Scale Observations Workshop 19

Figure 3.6: Cloud pressure over the Arctic for 10 April 1996 from the TOVS PathP data set.

terannual variations. Variables include cloud amount, cloud optical depth

(daytime), cloud temperature and pressure, cloud phase, surface clear sky

temperature, and visible reflectance. Data are currently available for 1983–

1998 and will ultimately continue through mid-2002. The spatial resolution

of the “D1” (3-hourly) and “D2” (monthly) data sets is 280 km, though a

30 km data set is also available. This is a global product. On the Web:

http://isccp.giss.nasa.gov/products/onlineData.html.

Wisconsin HIRS Cloud Climatology (satellite): The High resolution Infrared Sounder (HIRS), part of the TOVS sensor suite, is also

being used to generate a global cloud product at the University of Wisconsin. Variables include cloud amount, cloud emissivity and transmissivity, cloud height, and cloud temperature. The data set currently covers a

12-year period from 1989 to the present. The spatial resolution is 2◦ latitude by 3◦ longitude. An example is shown in Fig. 3.7. On the Web:

http://www.ssec.wisc.edu/∼donw.

3.4.2 Outlook: The next 5 years

Some of the data sets described above will be extended to include additional

years. The BSRN network will continue to collect data, the ISCCP data set

will be processed through 2002, the extended APP data set will cover the

years 1994–1998, and the Wisconsin HIRS cloud climatology will continue

indefinitely (a related project will generate a 22-year climatology by mid2002). Additionally, there is a possibility that the TOVS Path-P data set

will be used to generate surface shortwave and longwave fluxes, providing

another source of radiation information over a 20-year period. A comparison
20 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

Figure 3.7: Global cloud amount for July over the period 1989–1995 from the Wisconsin HIRS Cloud

Climatology project.

of the TOVS-derived surface radiative fluxes to measurements made during

SHEBA is given in Fig. 3.8 (A. Schweiger, personal communication).

3.5 Satellite Temperature Sounding Data

Jennifer Francis reported that the Television Infrared Observation Satellite (TIROS) Operational Vertical Sounder (TOVS) instrument has flown

on NOAA polar-orbiting satellites since 1979 and has collected one of the

longest and most complete satellite data records in existence. It was originally designed to serve the weather forecasting community by providing

temperature and moisture profiles in regions of the Earth that had few conventional meteorological stations. An example of lower stratospheric temperature anomalies for April months in the 1990s are shown in Fig. 3.9. Further

details are available in several reports by J. Francis at the workshop website.

Data from this sensor have shown potential for a wide range of climate applications. A problem arises in this context, however, as the radiances were not

adequately calibrated for long-term accuracy, hence substantial biases exist

in data from the various platforms. These biases have several sources, e.g.,

different sensor characteristics on each platform, instrument degradation,

orbital changes, and systematic errors in forward radiative transfer models.

Absolute and relative errors in the radiances reduce the potential value of

TOVS observations for monitoring and understanding climate change.

An opportunity for SEARCH is to address these errors for the Arctic.

Many of the known errors should be regionally and seasonally independent,
SEARCH Large-Scale Observations Workshop 21

Figure 3.8: Downwelling longwave (left) and shortwave (right) fluxes computed from the TOVS Path-P

data set (”Parameterized”) and measured at the surface over the SHEBA year.

but we suspect some may be peculiar to or exacerbated in Arctic conditions.

Thus, efforts should be primarily directed to the Arctic to produce a data set

of TOVS radiances with biases minimized. Once this has been completed,

the data should be of value both for geophysical retrievals with sufficient

accuracy to identify changes since 1979, and future changes, as well as for

direct assimilation by numerical atmospheric models for reanalyses.

One would begin by assessing techniques used by other experienced

groups—such as those who produce the NCEP and ECMWF reanalysis data

sets and long-term, global TOVS retrievals—to learn of the successes and

failures of their methods and/or data sets of corrections. A large number

of suitable, high-quality radiosonde profiles would need to be assembled and

matched with satellite observations coincident in space and time. This effort

would involve data rescue, sorting, and evaluating the quality of available

radiosonde data. Large numbers of data are needed so that random errors,

such as in radiosonde measurements and from satellite noise, can be removed

by averaging. By employing one or perhaps two well-characterized (in terms

of their biases in varying atmospheric conditions) forward radiative transfer models, we could calculate from the radiosonde/satellite match-ups the

corrections to TOVS radiances.

Another avenue of effort is to take advantage of periods when two satellites flew simultaneously. Radiances measured in close space and time proximity, as well as the retrievals from these radiances, can be compared to determine relative biases. This method may be particularly effective in polar

regions, as orbits converge in high latitudes, resulting in frequent overpasses

of the same area.

This effort would be an intensive multi-step process that would need to be

performed collaboratively at NOAA/NESDIS, NCEP and other institutions
22 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

Figure 3.9: An example of temperature anomalies in March for different years based on satellite temperature

profiling data.
SEARCH Large-Scale Observations Workshop 23

with TOVS expertise. A related but preliminary project is already underway at NOAA/NESDIS, which involves rescuing a data set of radiosondes

(so-called DSD5). Additional soundings will be needed from later periods

and for airmass types that are not well represented in the archived data

set. Converting TOVS retrievals from an operational data set to a climate

quality data over the data sparse Arctic areas will be a major tool for direct

study of atmospheric changes and for use in reanalysis projects, especially a

recommended Arctic system reanalysis as part of SEARCH.

3.6 Long-Term Intensive Atmospheric Observing Stations

3.6.1 Rationale

In addition to the distributed and satellite-based observing systems discussed

so far in this section, it is necessary to operate a small number of strategically

placed, long-term, intensive ground-based, atmospheric observing stations

on land with an option for making similar measurement sets on icebreakers,

at ice camps, and at field experiments. The primary purpose of such sites

would be to:  Make detailed measurements of key parameters over sufficient periods

to monitor climate change and assess seasonal and decadal climate

variability  Support interpretation and validation of satellite data  Provide measurement suitable for developing new model parameterizations  Provide measurements sufficiently detailed to conduct process studies

to advance fundamental understanding of Arctic atmospheric processes

Taneil Uttal and Bernie Zak commented on this approach.

3.6.2 Strategy

In developing a plan for intensive sites it is necessary to isolate the type, frequency, and accuracy of measurements required, to review existing facilities

and capabilities, and to determine optimum site selection within the logistic

constraints that are likely to be imposed by the Arctic environment.

Intensive sites would make continuous, long-term measurements of parameters such as spectral and broadband surface radiation fluxes, surface

albedo, clouds (fraction, vertical distribution, microphysics and optical properties), aerosols (chemical composition, optical depth, concentration, spatial distributions), Arctic haze, surface sensible heat and latent heat fluxes,

ozone, carbon dioxide greenhouse gases (CO2, O3, water vapor, NO2, CH4),

precipitation, and high quality, standard meteorological observations (pressure, temperature, winds, humidity).

Currently, and historically, sites are operated at Barrow, Alaska and

Kiruna, Sweden, with some observations in NE Canada and Svalbard. Figure 1.1 (left) shows a map of wintertime temperature trends for the Northern
24 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

DENMARK

NORWAY SWEDEN

GERMANY

ESTONIA

LATVIA

LITHUANIA

POLAND

BELARUS

UKRAINE

MOLDOVA

RUSSIA

CANADA

GREENLAND

ICELAND

ALASKA

IRELAND

UNITED

KINGDOM

FINLAND

20° 0° 20°

40°

60°

Arctic Circle

70°

80°

60°

80°

100°

120°

140°

160° 180°

140°

120°

100°

80°

60°

40°

160°

Arctic

Ocean

0 1000 2000 Miles

0 1000 2000 3000 Kilometres

Figure 3.10: Barrow is the present site of extensive atmospheric measurements.

The present concept would enhance measurements at existing stations, two possibilities being Alert and Svalbard, with eventual development at a third station in

Russia such as Tiksi. Red lines on the figure indicate a flight track for proposed

aircraft sorties which would monitor horizonal variability between stations.

hemisphere for the previous 50 years. There is large-scale spatial covariability, with warming trends over eastern Siberia and northwestern North America, and cooling over NE Canada and, to some degree, west of Bering Strait.

Inspection of Fig. 1.1 supports a priority recommendation of the importance

to augment intensive observations in NE Canada. This has been a region

of cooling, which is out of phase with the Barrow and Kiruna. To complete

the array, a location in Russia should be a future consideration.

The observing strategy envisioned is to develop widely distributed, largely

autonomous observing networks in conjunction with embedded, high intensity, manned observing stations at key locations. These observations would

optimally be supplemented with a program of annual aircraft sorties and

ship cruises that are performed on a regular basis from year to year to provide a measurement of large-scale horizontal variability (Fig. 3.10). The
SEARCH Large-Scale Observations Workshop 25

Figure 3.11: Fish eye lens view of the NOAA/CMDL Barrow Observatory.

aircraft and ship would provide a critical link with ocean/ice, satellite and

autonomous network observing programs. Finally, it is recommended that

a portable suite of instruments be developed that could be episodically deployed at ice stations, on ice breakers, and in land-based field campaigns to

complement fixed sites. The Barrow, Alaska site is discussed in some detail

in the following section.

3.6.3 The Barrow, Alaska site

The atmospheric measurements being made at the NOAA Climate Monitoring and Diagnostics Laboratory (CMDL) Baseline Observatory and the

Department of Energy Cloud Atmospheric Radiation Measurement Program

in Barrow, Alaska represent some of the most technologically advanced and

comprehensive measurements of the clouds, radiation, chemistry, and other

aspects of the physical atmosphere. The Barrow location and its unusually

strong complement of atmospheric sensors is unique not only in the Arctic

but also with respect to comparable stations throughout the world.

The CMDL observatory has the primary goal of monitoring the atmospheric constituents that are capable of forcing climate change and those

that may cause depletion of the global ozone layer. Measurements such as

meteorology, surface ozone, carbon dioxide, aerosols, and radiation began in

1972–1974 and are some of the longest continuous atmospheric records in

the Arctic. Today, over 200 different measurements are conducted at the

Barrow Observatory through 35 cooperative programs (Fig. 3.11).

The DOE ARM North Slope of Alaska (NSA) facility adjacent to the

NOAA site commenced measurements of key radiation and cloud measurements in February 1998. The radiation measurements are made by a number
26 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

Ice and Liquid Water Content, Aug 09, 2000

IWC in blues and LWC in reds (mg/m3)

0.001 0.014 0.064 0.170 0.500

0 5 10 15 20

0.000 0.003 0.015 0.045 0.100

12

10

8

6

4

2

0

10

8

6

4

2

0

Tau (LW, absorption) Height [km, AGL]

TERRA, 29.94

Time (hours, GMT)

TERRA, 20.99

Figure 3.12: Time-height (24 hours, 0–12 km AGL) cross section of radar and radiometer cloud water

content retrievals for a low level all liquid boundary layer cloud at the surface and an all-ice liquid cloud in

the upper atmosphere. TERRA satellite overpass times are indicated in red, NOAA satellite overpasses are

indicated with dashed lines.

of broad-band and spectral sensors, which are complemented by state-ofthe-art cloud measurements from millimeter cloud radar, and micropulse

lidar. By combining measurements from these passive and active sensors,

time-height records of detailed cloud properties can be derived which are

important in assessing cloud effects on atmospheric heating profiles and

atmosphere-surface heat and exchanges (Fig. 3.12).

The Barrow station, including a strong history of community support,

serves as a prototype for enhanced atmospheric measurements that would

be highly desirable at other key locations in the circumArctic.

3.7 Data Archives

Florence Fetterer has summarized 24 Arctic data sets in a report at the workshop web site, http://www.epic.noaa.gov/SEARCH/obs/workshop/

reports.shtml. These data are available at NCDC, National Snow and

Ice Data Center (NSIDC), and other centers.

SEARCH needs to move beyond logging data sets, which is being handled

well by various data centers, including satellite data at various Distributed

Active Archive Centers (DAACs).
SEARCH Large-Scale Observations Workshop 27

Taking a cue from the previous chapter on developing a detection strategy, these data should be developed into multiple lines of evidence for Arctic

change, and referenced at one web site, a SEARCH virtual observation and

detection location. Information at this site should be updated frequently,

at least quarterly, and include biological and physical data. Value-added

studies could be posted at this site.

Arctic-wide data sets of quality controlled data with at least a 30-year

record length are necessary for addressing the detection problem. Data sets

from Eurasia for precipitation (liquid and solid), radiation, river discharge,

snow depth (water equivalent), sea ice, and soil temperature that are available to SEARCH researchers are incomplete. While the scope of the work

needed varies for each parameter, the tasks that must be performed are:  Catalogue data sources: How complete is the existing record, and where

do data that can fill gaps reside? Can additional data be acquired, how

soon, and at what cost? This information must be compiled before the

scope of the data rescue effort can be determined.  Assess data quality: How were the data digitized and documented?

Were quality control routines preformed on the data? Are they needed?  Update the record: Former Soviet Union snow data, monthly precipitation and evaporation data, meteorological data from Russian coastal

stations, and Russian river ice thickness and duration data sets are

available to researchers but are current only through the early 1990s.

We need to update these data sets through 2001 where possible.  Extend the record back in time and fill spatial and temporal gaps: For

example, soil temperature data from China and Mongolia (87 stations)

and Russia (140 stations) are available and require resources for quality control and publication. These data help cover a data sparse area.

Meteorological data from Russian stations that are internationally exchanged represent about 10% of the national station network. Most of

these station records date back at least to the early 1950s and in some

cases the 1930s.

Once the complete data record is obtained, data sets need to be prepared

so that they can be used directly to address detection problems. This will

usually involve (a) statistical characterization of the data set with additional

quality control routines, (b) providing a browse capability, (c) providing

documentation, metadata and cataloguing the data, and (d) gridding the

data set for easy visualization, computation of modes of variability, and

cross correlation with other data sets.

Two examples illustrate the type of work that needs to be done to complete the historical record (for Russian radiation data) and to re-establish

near-real-time data broadcasting (for Arctic hydrology).

3.7.1 Russian radiation data

The Global Energy Balance Archive (GEBA) database is the primary source

for digital radiation data, but it contains little data from the former Soviet
28 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

Union. Mean monthly or monthly totals of solar radiation parameters from

the Russian North Pole (NP) drifting station program were published in

“Handbook of the Radiation Regime of the Arctic Basin (Results from the

Drift Stations)” by Marshunova and Mishin, edited by Radionov and Colony.

To complete the historical record of Russian Arctic radiation measurements,

the Arctic and Antarctic Research Institute (AARI) in St. Petersburg should

be contracted to prepare synoptic (4 times daily) radiation data from the

NP stations. These data date from the 1950s through 1991. In addition,

AARI should be funded to prepare any available radiation data from land

stations (AARI has proposed digitizing global radiation and cloud type from

12 stations back to 1936).

3.7.2 Arctic hydrology network

Due to a reduction in the number of river discharge gauges, the Arctic

drainage basin area monitored has decreased by 67% from 1986 through

1999, at a rate of 79% in Russia and 59% in North America. The reduction is due primarily to budget cuts, compounded in Russia by the loss of

qualified personnel to staff remote stations (Shiklomanov et al., 2001). It is

a critical problem because data from smaller sub-basins are needed to measure the spatial variability of runoff, but gauges from smaller rivers have been

eliminated preferentially. A prototype project, the Arctic Rapid Integrating Monitoring System (Arctic-RIMS), has begun to organize a continuous

operational river discharge monitoring system by compiling near-real-time

daily discharge data for a selection of 56 gauges. It is a collaborative project

between U.S. researchers and the Arctic and Antarctic Research Institute,

St. Petersburg. SEARCH has a unique opportunity to leverage the work

being done under Arctic-RIMS by supporting the reestablishment and maintenance of gauge stations in Russia that will help characterize the hydrologic

cycle beyond the freshwater flux to the Arctic Ocean (which is the emphasis

of Arctic-RIMS). Much of the time-consuming process of making contacts

in Russia and identifying the most important gauge stations has already

been done. SEARCH should begin planning to strengthen and expand the

Arctic-RIMS network so that near-real-time delivery of data continue after

the completion of Arctic-RIMS in 2005.

3.8 References

Francis, J., and A. Schweiger (1998): The NASA/NOAA TOVS Polar Pathfinder:

18 Years of Arctic data. American Meteorological Society 5th Conference on

Polar Meteorology and Oceans, 24, 128–143.

Hahn, C.J., S.G. Warren, and J. London (1996): Edited Synoptic Cloud Reports

from Ships and Land Stations Over the Globe, 1982–1991. Carbon Dioxide

Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, TN.

Key, J., D. Slayback, C. Xu, and A. Schweiger (1998): New climatologies of polar

clouds and radiation based on the ISCCP “D” products. American Meteorological Society 5th Conference on Polar Meteorology and Oceans, pp. 227–232.

Maslanik, J., C. Fowler, J. Key, T. Scambos, T. Hutchinson, and W. Emery (1998):

AVHRR-based Polar Pathfinder products for modeling applications. Annals

Glaciol., 25, 388–392.
SEARCH Large-Scale Observations Workshop 29

Polyakov, I.V., and coauthors (2002): Observationally based assessment of polar

amplification of global warming. Geophys. Res. Lett., submitted.

Schweiger, A.J., R.W. Lindsay, J.R. Key, and J.A. Francis (1999): Arctic clouds in

multiyear satellite data sets. Geophys. Res. Lett., 26(13), 1845–1848.

Serreze, M.C., J.R. Key, J.E. Box, J.A. Maslanik, and K. Steffen (1998): A new

monthly climatology of global radiation for the Arctic and comparisons with

NCEP-NCAR reanalysis and ISCCP-C2 field. J. Climate, 11, 121–136.

Shiklomanov, A.I., R.B. Lamners, and C.J. V ̈or ̈osmarky (2002): Widespread decline

in hydrological monitoring threatens pan-Arctic research. Eos Trans. AGU, 83,

13, 16–17.

Wylie, D., and W.P. Menzel (1999): Eight years of high cloud statistics using HIRS.

J. Climate, 12, 170–184.
30 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh
SEARCH Large-Scale Observations Workshop 31

4. Terrestrial Observations

Compiled by Dave McGuire with contributions from Terry Chapin, Torben

Christensen, J. Dong, Claude Duguay, Barry Goodison, Florence Fetterer,

Larry Hinzman, John Hobbie, Ed Josberger, Ranga Myneni, Walt Oechel,

Vladimir Romanovsky, Marilyn Walker, Bernie Zak, and Liming Zhou.

4.1 Introduction

Evidence continues to mount that warming experienced in the Northern

Hemisphere during the past few decades has been affecting terrestrial ecosystems in high latitude regions (Oechel et al., 1993, 2000; Kurz and Apps,

1999; Osterkamp and Romanovsky, 1999; Barber et al., 2000; Serreze et al.,

2000; Stocks et al., 2000; Sturm et al., 2001; Silapaswan et al., 2001). These

changes are affecting the function and structure of upland and freshwater

aquatic ecosystems, and it is important to understand the nature of these

changes as they have implications for human livelihoods in high latitude

regions and elsewhere through effects on subsistence resources, commercial

fisheries resources, infrastructure, and industrial activity (e.g., oil and gas

development). As climate changes in high latitudes are expected to be amplified in comparison to temperate and tropical latitudes, it is also important

to understand how spatial and temporal variability in climate is affecting

spatial and temporal variability in high latitude terrestrial ecosystems, as

this understanding will provide insight that is relevant to understanding

responses to climate change in other terrestrial regions. Changes in high latitudes may also have consequences for the functioning of the Arctic System

that are associated with (a) water and energy exchange with the atmosphere,

(b) the delivery of fresh water to the Arctic Ocean, and (c) the exchange of

radiatively active gases with the atmosphere (Chapin et al., 2000; Forman

et al., 2000). It is important to understand terrestrial changes that have

consequences for the Arctic System because these responses may affect the

rate and magnitude of changes that occur in high latitudes and elsewhere.

Four important points emerged from the workshop on the nature of terrestrial observation networks. First, observation networks need to be designed

so that they provide information on how spatial and temporal variability in

climate is affecting spatial and temporal variability in high latitude terrestrial

ecosystems. This insight is relevant to understanding responses to climate

change that have implications for human livelihoods in high latitude regions

and elsewhere. Second, the spatial domain of terrestrial ecosystems that has

potential to influence the Arctic System extends far beyond the boundaries

of “tundra” and should include the land mass that contributes fresh water

inputs to the Arctic Ocean (see Fig. 4.1), i.e., north of 40◦N. Third, changes

in terrestrial ecosystems that may have consequences for the Arctic System

or that may indicate large-scale impacts of changes in the Arctic System include changes in (a) land cover, (b) snow cover, (c) soil thermal regime, (d)

terrestrial glaciers, (e) lakes and wetlands, (f) hydrology, and (g) trace gas

exchanges. Finally, changes in these features of terrestrial ecosystems may

simultaneously influence the different climatic feedbacks relevant to the Arc-
32 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

tic System. For example, changes in land cover or in permafrost dynamics

simultaneously influence water and energy exchange, hydrology, and the exchange of radiatively active gases. Observation systems should be designed

so that the systems can contribute to sorting out the net effect of the various

feedbacks to the Arctic System (e.g., see Betts, 2000).

Presentations and discussions at the SEARCH Observations Workshop

provided information on terrestrial feedbacks to the Arctic System, on the existing observation networks, and on the studies that have identified changes

in various features of high latitude terrestrial ecosystems. Of particular

relevance are the network of the International Geosphere Biosphere Program (IGBP) high latitude transects, the Land Atmosphere Ice Interactions

(LAII) research efforts of the Arctic System Science Program (ARCSS), and

the two Long Term Ecological Research (LTER) sites in Alaska located at

Toolik Lake and Bonanza Creek (see Fig. 4.2). Below we provide a limited

set of key recommendations for SEARCH to consider as priority in its efforts to establish networks for high latitude terrestrial observations. Then

we present a summary of the opportunities for continuing and enhancing observations for the various features of high latitude terrestrial ecosystems that

emerged from the workshop. Finally, we provide a comprehensive summary

of the information on terrestrial observations presented at the workshop to

document the rationale that led to the opportunities that we identify and

recommendations that we make. A partial summary of potential terrestrial

observations is presented in Table 4.1

4.2 Key Recommendations for Continuing/Enhancing High

Latitude Terrestrial Observations

Below we provide a set of recommendations for the SEARCH effort to continue and enhance high latitude terrestrial observations. These recommendations are based on our judgment that implementation of these recommendations will provide important information on how spatial and temporal

variability in climate is affecting spatial and temporal variability in highlatitude terrestrial ecosystems. We also feel that the implementation of

these recommendations will provide some information relevant to how highlatitude terrestrial ecosystems influence the climate of the Arctic System

through water/energy exchange, freshwater flux to the Arctic Ocean, and

the exchange of trace gases with the atmosphere. Our recommendations are

also based on our perspective that SEARCH efforts should build on LAII

research (e.g., ITEX, FLUX, ATLAS), on LTER Research (Toolik and Bonanza Creek LTERs), and should build on international efforts (IGBP, EU,

Japanese, and Canadian). The recommendations represent a limited set of

the opportunities identified above with the perspective that initial resources

committed by SEARCH should be devoted to these issues, and other issues should receive attention as additional resources for SEARCH become

available. The terrestrial observations supported by SEARCH will be most

valuable to advancing scientific understanding of terrestrial responses and

variability if they are integrated with process and modeling studies. Also,

it is important that information from observation networks and process and
SEARCH Large-Scale Observations Workshop 33

Figure 4.1: The pan-Arctic drainage basin. Figure from Forman et al. (2000).
34 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh 80 ̊ 70 ̊ 60 ̊ 50 ̊50 ̊ 60 ̊ 70 ̊ 80 ̊

Alaska

BFTCS

Finland ScanTran

EST

FEST

FLUX/ATLAS Research Sites

Alaska LTER Research

IGBP High Latitude Transects

Vegetation types

Ice

Polar desert/Alpine tundra

Moist tundra

Forest – tundra

Boreal forest

Extra - boreal

Figure 4.2: Polar projection vegetation map indicating the location of high latitude transects. Also shown

are the locations of ARCSS-LAII research sites from the FLUX and ATLAS efforts and the locations of the

Toolik and Bonanza Creek Long Term Ecological Research Sites in Alaska. Figure is based on figure from

McGuire et al. (2002).
Table 4-1: A partial listing of existing observation networks for parameters that are changing features of terrestrial ecosystems. In the “Feedbacks” column, R is for radiative forcing, H represents hydrology, and C is for carbon and methane. Primary existing observation program, Spatial coverage Temporal coverage Other relevant 

Parameter network, and/or data set Observation method and resolution and frequency Comments information sou

Land Cover Treeline Individual researchers Tree rings (“forest demographics”) Individual sites, but pan-Arctic. Resolution varies Change has a 100-year time scale. Need observations every 5 years to capture change relevant to AO Remote sensing a possibility, but only on long (50-year) time scale. Need for periodic obs. campaigns ATLAS 

Shrubs ITEX Passive warming experiment Individual sites (of several m-sq plots), but pan-Arctic 11-year time series Remote sensing (and photography) possible with TM & ETM at sub-decadal intervals ATLAS Growing Season AVHRR studies Remote sensing (well developed application) N. hemisphere, 1 km and 8 km Sub-monthly, 1981–present Can use growing degree days for proxy [Boston University 

Disturbance (e.g., fire)— extent and severity AK (BLM) and Canada (CFS) large fire scar data base Fire records, plus remote sensing AK, Canada, at about 1 km AK: 1950–present Canada: 1960–present Need fire data base for northern Eurasia and other disturbance data bases for pan-Arctic (e.g., logging, insect defoliation) Alaska fire service 

Snow Cover Extent NOAA operational snow product Optical remote sensing, with passive microwave beginning in 1999 N. hemisphere, 25 km Gridded 25 km weekly product from NSIDC incorporating NOAA analysis: 1971–1995. Daily operational product from NOAA/NESDIS: 1997–present Possible discontinuity in NOAA product in 1999. 500 m gridded product from MODIS instrument: 2000–present NOAA/NESDIS C

Prediction CenterNOAA/NESDIS SServices Division 

Depth National (U.S., Russia, Canada) obs. networks, a standard obs. at synoptic and climate stations Manual. Remote sensing of depth is immature application Point measurements, limited number of transects Daily beginning in 1950s, earlier for some stations Closure of stations, and change to automatic methods impacting consistency and coverage Global Climate O

System 

SWE National (U.S., Russia, Canada) networks Snow course, some automated sensors. Remote sensing of depth is an emerging application. Point measurements, limited number of transects. Satellite-derived Canada product Varies, daily to 10-day. Daily (if satellite derived) Decline in number of snow course measurements NASA Cold Land

(CLP) experiment sensing validationCRYSYS program 

Soil Thermal Regime Permafrost/seasonally frozen ground extent Int. Permafrost Asso. map (CAPS CD-ROM) Developed based on expert opinion, not observations Northern hemisphere. Gridded version (12.5 km) available Static Need pan-Arctic map of better spatial resolution, based on observations IARC/WDC Froz

Data Center 

Active Layer Depth CALM network Individual stations Pan-Arctic Measured annually Network record not long enough yet to evaluate for monitoring trends. Need to re-establish and maintain borehole transect network Temperature, freeze/thaw duration Existing borehole sites, e.g., IGBP trans-Alaskan boreholes (incorporation of these and others in GTMP network proposed) Boreholes Pan-Arctic, point measurements, limited number of sites with multiple boreholes Varies by borehole, generally longer than 20 years. Weekly to monthly needed in uppermost 20 m, annually to every 10 years at greater depths [from GTOS requirement] Timing of freezing, thawing, may be detectable with remote sensing. NASA CLP program is investigating GTMP network. GCOS–Global Ter

Network for Perm
Table 4-1: (continued). Primary existing observation program, Spatial coverage Temporal coverage Other relev

Parameter network, and/or data set Observation method and resolution and frequency Comments information 

Terrestrial Glaciers Mass Balance World Glacier Monitoring Service In situ (stake) measurements. Airborne laser campaigns Pan-Arctic Needed annually Large glaciers not well documented. Reduction in the number of glaciers monitored since 1980s GCOS-Glob

Network for University oprograms for 

Parameter (e.g., length, elevations, area) World Glacier Monitoring Service In situ measurements, remote sensing measurements soon to come Pan-Arctic Length: needed annually to every 10 years. Inventory parameters: every 30–50 years GLIMS proj

parameters f

Lakes and Wetlands Ice cover duration LIAG Global Lake and River Ice Phenology Database In situ observations, with remote sensing an emerging application About 270 northern hemisphere lakes in LIAG data base Annual ice on, ice off dates Canada Ice S

programs. LGroup (LIAG

Areal extent of lakes and wetlands There is a need to monitor a selection of lakes, with change detection studies 

Hydrology CHAMP, RI

network) Precipitation National networks Intercomparison studies show serious differences in obs. from different nations 

Runoff National networks Gauging stations Pan-Arctic stations 1930–present (Russia), 1970–present for AK and Canada The number of operational gauge stations has decreased Arctic-RIMS 

underway sin

Soil moisture There is a need for this product. Remote sensing validation issue? 

Water constituents Russian network ARCSS project to evaluate data quality USGS starti

program in Y

Trace Gas Exchange (CO2/Methane) Loose pan-Arctic network of investigators Chambers, eddy covariance towers Individual pan Arctic sites, 1 m to 1 km 1970’s–present, duration depends on investigator. Most focus on growing season. (Need winter as well) ATLAS, CO

BOREAS, Nstudies, LAI[access data distributed dJOSS] 

Siberian tall tower One 600 m eddy covariance tower Central Siberia, about 1000 km × 1000 km area covered Under construction Max Plank Institute involved Aircraft campaigns Aircraft gas sampling Siberia, continental spatial scope Monthly, for 1 year, in 2001 or 2002 Max Plank Institute involved
SEARCH Large-Scale Observations Workshop 37

modeling studies ultimately be incorporated into coupled models of the Arctic System at the pan-Arctic scale. From the set of opportunities in the

following Section 4.3, we highlight the following five recommendations:  SEARCH should provide resources for maintaining the operation of

U.S. ITEX sites, as the International ITEX data set now has information on changes in vegetation communities over the last decade. This

should be combined with extensive calibration and use satellite-based

vegetation indices over the Arctic basin.  SEARCH should provide resources to ensure the maintenance and,

where possible, the re-establishment of long-term monitoring of permafrost and glacier mass balance. Resources are needed for upgrading

equipment and for providing maintenance of Russian borehole sites and

the sites along the Alaskan IGBP transect already in existence and for

the re-occupation of abandoned USGS borehole sites in Alaska. Similarly, for glaciers, resources are needed to maintain current monitoring

efforts and re-establish programs on glaciers in critical regions.  SEARCH should provide resources for monitoring a key selection of

lakes throughout the pan-Arctic for break-up dates, freeze-up dates, and

changes in lake size.  SEARCH should coordinate with ARCTIC-CHAMP to determine how

it can best provide operational assistance to that effort.  SEARCH should provide some support for the operation of key sites

that are comprehensively monitoring how climatic variability influences

variability in water, energy, and trace gas exchange (e.g., eddy covariance sites); priority for support should go to sites that are currently

providing long-term records of observations and for sites that have a

history of long-term studies of processes.

4.3 Opportunities for Continuing and Enhancing High Latitude Terrestrial Observations

4.3.1 Land Cover

Key observational opportunities for detecting changes in land cover in

SEARCH are to (1) maintain continuity of the ITEX measurements, (2)

conduct analyses of AVHRR and MODIS imagery that are more relevant to

the high latitudes than the global analyses that have been conducted in the

past, (3) conduct change-detection studies of Landsat and other fine-scale

imagery to determine the extent of shrub expansion throughout the panArctic, (4) conduct periodic campaigns for determining the extent of treeline expansion throughout the pan-Arctic, and (5) assist in the development

of an operational capability for monitoring the extent of fire disturbance in

Russia and insect infestations in North America.
38 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

4.3.2 Snow Cover

Existing operational snow extent estimates from NOAA are probably adequate for evaluating changes in snow extent. NOAA’s Office of Research and

Applications is currently compiling these products on a CD-ROM of snow

and land cover from 1981-present. There are difficulties for water content.

4.3.3 Soil Thermal Regime

The maintenance of a high latitude network of five borehole transects (one

in Alaska, two in Canada, and two in Siberia) would provide the capability to monitor permafrost temperature with depth, active layer depth, soil

moisture, and changes in freeze-thaw dynamics in a manner that is relevant

to the Arctic System. The network could become operational with a modest investment in equipment and maintenance for the Russian borehole sites

and for the re-occupation of abandoned USGS sites in Alaska. Network data

management is an issue that needs to be resolved.

4.3.4 Glaciers and Ice Sheets

While satellite remote sensing of glacier mass balance is improving as resolution increases, there are still a number of issues that need to be resolved

before it is fully operational. Fieldwork is generally expensive, but a stake

network for Arctic glaciers might be effective as ablation and accumulation

rates are small. Aircraft airborne laser campaigns represent the best means

of currently assessing volumetric changes for glaciers and ice sheets. New observational programs should, where feasible, be undertaken on glaciers that

have been the subject of mass balance studies in the past.

4.3.5 Lakes and Wetlands

There is an opportunity for SEARCH to monitor a selection of lakes throughout the pan-Arctic for break-up and freeze-up dates using in situ methods. The selection of lakes may usefully be stratified by drainage basins,

ecoregions, and lake size (large vs. small). Currently, satellite remote sensing of break-up and freeze-up dates is a research and development activity

rather than an operational activity. There is also the opportunity to conduct change-detection studies of Landsat and other fine-scale imagery to

determine whether changes in lake area represent interannual variability or

represent longer term trends.

4.3.6 Hydrology

There are opportunities for SEARCH (1) to initiate a monitoring network for

soil moisture, (2) to assist with occupying and maintaining key discharge stations that are at risk or have ceased operation, and (3) to assist in the effort

to rescue Russian data into pan-Arctic and global archives. Remote sensing

research and development should be focused toward ultimately providing the

capability to provide an operational soil moisture product. SEARCH should
SEARCH Large-Scale Observations Workshop 39

coordinate with ARCTIC-CHAMP to determine how it can best provide

operational assistance to that effort.

4.3.7 Trace Gas Exchanges

There are opportunities for SEARCH to support the continued operation of

currently operating eddy covariance sites along with the expansion of eddy

covariance sites for key sites. Higher priority for support should go to sites

that are providing longer records of observations and for sites that have a

history of long-term studies of processes (e.g., the two LTER sites in Alaska).

If intensive sites for ground-based monitoring of atmospheric processes (e.g.,

the DOE ARM/NOAA CMDL site at Barrow) are installed around the panArctic by SEARCH, then eddy covariance sites should be established along

with associated process studies as the exchanges of trace gases are coupled

with exchanges of water vapor and energy with the atmosphere. SEARCH

should also consider how it can augment and enhance the tall tower and

aircraft campaigns that are just being initiated in Siberia. SEARCH should

also consider to what extent it can assess the quality of extant data on DOC

and other river constituents that have been archived and to rescue data that

have not been archived into an operational pan-Arctic data base of DOC

and other constituents.

4.4 Review of Information Presented on High Latitude Terrestrial Observations—Background on Terrestrial Feedbacks Relevant to the Arctic System

Responses of high latitude ecosystems to global change have the potential to

influence water and energy exchange with the atmosphere in several ways.

Expansions of shrub tundra into regions now occupied by sedge tundra and

of boreal forest into regions now occupied by tundra have the potential to

reduce growing season albedo and increase spring energy absorption to enhance atmospheric warming (Bonan et al., 1992; Thomas and Rowntree,

1992; Foley et al., 1994; Chapin et al., 2000; Beringer et al., 2002). Other

effects that may enhance atmospheric warming through decreased albedo include extension of the snow-free and ice-free periods on terrestrial and lake

surfaces. Also, reduction in the area occupied by glaciers and continental ice

sheets in high latitudes may reduce albedo; similarly, changes in the area of

lakes or in the area occupied by open water in wetlands may affect albedo.

Disturbance may also affect energy exchange with the atmosphere. For example, while fire disturbance often reduces albedo to approximately 0.05

shortly after the fire, fire disturbance provides the opportunity for deciduous forests to develop, which generally have higher albedo in comparison

to conifer forests. Thus, disturbance regimes (e.g., fire) that increase the

proportion of non-forested lands and deciduous forests have the potential to

reduce energy absorption and work against atmospheric warming (Chapin

et al., 2000).

The delivery of freshwater from the continental land mass is of special importance to the Arctic Ocean since it contains only about 1% of the world’s
40 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

ocean water, yet receives about 11% of world river runoff (Shiklomanov et

al., 2000; Forman et al., 2000); the Arctic Ocean receives fresh water inputs

from four of the fourteen largest river systems on earth (Forman et al., 2000).

Additionally, the Arctic Ocean is the most river-influenced and land-locked

of all oceans and is the only ocean with a contributing land area greater

than its surface area (Ivanov, 1976; V ̈or ̈osmarty et al., 2000a). Freshwater

inflow contributes as much as 10% to the upper 100 meters of the water

column for the entire Arctic Ocean (Barry and Serreze, 2000). Changes in

fresh-water inputs to the Arctic Ocean have the potential to alter salinity

and sea ice formation, which may have consequences for the global climate

system by affecting the strength of the North Atlantic Deep Water Formation (Aagaard and Carmack, 1989; WMO/WCRP, 1994; Broecker, 1997).

Modeling studies suggest that maintenance of the thermohaline circulation

is sensitive to fresh-water inputs to the North Atlantic (Manabe and Stouffer, 1995). Also, freshwater on the Arctic continental shelf more readily

forms sea ice in comparison to more saline water (Forman et al., 2000). The

responses of freshwater inputs to the Arctic Ocean depend on changes in

the amount and timing of precipitation, and the responses of permafrost dynamics, vegetation dynamics, and disturbance regimes to global change. For

example, changes in evapotranspiration associated with permafrost and vegetation dynamics have consequences for river runoff that depend additionally

on changes in precipitation inputs to terrestrial ecosystems.

Increases in the atmospheric concentrations of radiatively active gases

have the potential to influence the climate through altering the earth’s nearsurface energy balance (IPCC, 2001). Responses of high latitude ecosystems

have the potential to influence the atmospheric concentrations of the radiatively active gases carbon dioxide and methane in several ways (Smith and

Shugart, 1993; McGuire and Hobbie, 1997; McGuire et al., 2000a, 2000b;

Chapin et al., 2000). High latitude ecosystems contain approximately 40%

of the world’s soil carbon inventory that is potentially reactive in the context of near-term climate change (McGuire et al., 1995; Melillo et al., 1995;

McGuire and Hobbie, 1997). Regions affected by permafrost are especially

vulnerable to climate change because of altered drainage. Thermokarst activity that leads to the expansion of lakes and wetlands may cause increased

releases of methane from high latitude ecosystems (Reeburgh and Whalen,

1992; Zimov et al., 1997). Reductions in the water table of tundra ecosystems substantially enhances the release of carbon from high latitude soils

(Oechel et al., 1995; Christensen et al., 1998). The replacement of tundra

with boreal forest might initially decrease but eventually increase carbon

storage in high latitudes (Smith and Shugart, 1993), with time lags and

rates of change that are sensitive to the rate and variability of climate change

(Chapin and Starfield, 1997). Disturbance in the boreal forest region may

substantially influence regional carbon exchange with the atmosphere (Kurz

and Apps, 1999; Dargaville et al., 2002). The responses of carbon storage

in high latitude ecosystems have important implications for the rate of CO2

accumulation in the atmosphere and international efforts to stabilize the

atmospheric concentration of CO2 (Smith and Shugart, 1993; McGuire and

Hobbie, 1997; McGuire et al., 2000b; Betts, 2000). In particular, it is impor-
SEARCH Large-Scale Observations Workshop 41

tant to understand how the global energy balance implications of changes in

trace gas exchanges of high latitude terrestrial ecosystems trade off against

or contribute to responses of regional energy balance associated with changes

that influence water and energy exchange in high latitudes (Betts, 2000).

Changes in terrestrial ecosystems that may have consequences for the

Arctic System or that may indicate large-scale impacts of changes in the Arctic System include changes in (a) land cover, (b) snow cover, (c) soil thermal

regime, (d) terrestrial glaciers, (e) lakes and wetlands, (f) hydrology, and

(g) trace gas exchanges. Observation networks that monitor changes that

affect these aspects of high latitude terrestrial ecosystems have the potential

to provide information on how spatial and temporal variability in climate is

affecting spatial and temporal variability in high-latitude terrestrial ecosystems. This insight is relevant to understanding responses to climate change

that have implications for human livelihoods in high-latitude regions and

elsewhere. Below, we review information provided at the workshop on these

aspects of high latitude terrestrial ecosystems.

4.4.1 Land Cover

Key issues of land cover change in high latitude regions relevant to the Arctic

System include expansion of treeline at the expense of tundra, expansion of

shrub tundra at the expense of sedge tundra, changes in vegetation leaf area

and growing season length, and changes in disturbance extent and severity.

The importance of improving the representation of the effects of land

cover in climate re-analyses was highlighted by the fact that incorporation

of improved information on albedo from the Boreal Ecosystem Atmosphere

Study (BOREAS) in the recent ECMWF re-analysis (Viterbo and Betts,

1999). This resulted in a 2◦C January warm bias for northern hemisphere

in comparison with a 13◦C January cold bias that was present in the prior

ECMWF re-analysis. Information presented on land cover changes include

documented expansion of treeline on the Seward Peninsula in Alaska and

elsewhere (Lloyd et al., 2002), documented expansion of shrub tundra on

the Seward Peninsula and North Slope in Alaska (Silapaswan et al., 2001;

Sturm et al., 2001), documented changes in growing season length in Alaska

(Keyser et al., 2000), and a doubling of annual area burned in the boreal

forest of North America during the last 20 years in comparison with earlier decades (Stocks et al., 2000). Analyses of northern hemisphere NDVI

over the last two decades are consistent with expanding growing seasons,

greater growth of trees, and expansion of shrub tundra (Fig. 4.3; Myneni et

al., 1997, 2001; Zhou et al., 2001). The International Tundra Experiment

(ITEX) is a pan-Arctic network of sites (Fig. 4.4a) using a common passive

temperature manipulation (see Fig. 4.4b) to examine variability in species

responses across climatic and geographic gradients of tundra ecosystems over

the last decade (Henry and Molau, 1997; Arft et al., 1999). Results indicate

that leaf bud burst and flowering are occurring earlier on warmed plots, but

that there has been little effect on the termination of growth at the end of

the growing season (Arft et al., 1999). ITEX measurements have also docu-
42 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

Figure 4.3: Changes in May to September NDVI from 1982–86 to 1995–99 across

the northern hemisphere. Based on data from Zhou et al. (2001) and Myneni et al.

(2001).

mented greater growth of shrubs in both control and passive warming plots

(Fig. 4.4c).

While treeline expansion on the Seward Peninsula is detectable with

ground-based tree-ring studies (Lloyd et al., 2002), it does not appear to be

detectable over the last two decades with Landsat imagery (Silapaswan et

al., 2001). The expansion of shrub tundra in Alaska is detectable with comparisons between historical (circa 1940s) and contemporary photographic

imagery (Sturm et al., 2001) and Landsat imagery (Silapaswan et al., 2001).

Silapaswan et al. (2001) demonstrated that the expansion of shrub tundra

is detectable with Landsat imagery at decadal and sub-decadal resolution.

Changes in vegetative leaf area and growing season length appear to be detectable via analyses of AVHRR imagery (Myneni et al., 1997), and other

satellite technologies (e.g., microwave; see Running et al., 1999a) show some

promise for monitoring changes in growing season length. In comparison

with analyses of AVHRR imagery, it is anticipated that analyses of MODIS

imagery will provide better information on changes in vegetative leaf area

and growing season length. ITEX currently provides a pan-Arctic network of

sites that is measuring changes in vegetation phenology, growth, and reproduction throughout the Arctic. The capability for monitoring the extent of

fire disturbance is already operational in Alaska and Canada (Murphy et al.,

2000; Stocks et al., 2000), but information on the extent of fire disturbance

in Russia is currently not reliable.
SEARCH Large-Scale Observations Workshop 43

a 

b 

-2

0

2

0-3 yr 4-6 yr

Effect Size (d)

Deciduous Shrubs

c

Figure 4.4: (a) Location of the International Tundra Experiment (ITEX) research sites across the panArctic. (b) Contol and passive warming plots at the Toolik Lake ITEX site in Alaska. (c) Effect size of

passive warming on shrub cover. Figure provided by M. Walker, University of Alaska Fairbanks.
44 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

4.4.2 Snow Cover

Key parameters of snow cover include snow extent, snow water equivalent,

and snow depth.

Beginning in 1972, snow extent was operationally derived by NOAA from

AVHRR/GOES imagery for the northern hemisphere at 25 km spatial resolution and weekly temporal resolution. Since 1999, the snow extent product

has produced daily from a variety of satellite sources including passive microwave imagery. A 4 km product will be available this year. NOAA is

moving toward fully automated processing, and expects to produce a twice

daily product at 1 km resolution by 2004. A daily 500 m gridded snow cover

product from the MODIS instrument has been available since September

2000. NCAR has some gridded snow cover from 1966 on. Serreze et al.

(2000) summarize analyses of NOAA and other snow data sets and find that

Northern Hemisphere snow cover has decreased by about 10% since 1972,

due primarily to less snow in spring and summer.

4.4.3 Soil Thermal Regime

Key parameters of the soil thermal regime in high latitude terrestrial regions

include permafrost temperature, active layer depth, seasonal freeze-thaw

dynamics, and permafrost extent.

The permafrost thermal regime with depth is a natural low-pass filter

that is capable of recording climatic variability on decade-to-century time

scales. A north-south network of boreholes in Alaska that has been operational since 1983 has documented that permafrost temperatures at 20 m

depth have been increasing over the past two decades. The Alaska borehole

network identifies the value of measuring the permafrost thermal regime

along transects, which is more valuable than randomly placed individual

boreholes. Boreholes already exist along four other possible transects: (a)

in Western Canada, (b) in Eastern Canada, (c) in western Siberia, and (d)

in eastern Siberia (see Fig. 4.5a). The Canadian Geological Survey is making measurements for the borehole transect in Western Canada, while Laval

University in Quebec is making measurements for the borehole transect in

Eastern Canada. There are quality control problems with the borehole data

being collected in Russia, primarily because of poor equipment. The Russian borehole sites could be made operational for a modest investment in

equipment and maintenance. Re-occupation of some boreholes previously

maintained by USGS in Alaska would also provide some valuable data as

there are several decades of data available for these sites prior to the 1990s.

Important issues to resolve in establishing a global network of five transects is

to determine what obstacles exist to making data available in timely fashion

and what is required to overcome those obstacles.

Active layer depth is being monitored across the pan-Arctic by the Circumpolar Active Layer Monitoring Network (CALM; Hinkel et al., 2002).

Interannual variability in active layer depth at a particular site is primarily

related to interannual variability in summer air temperature. Longer-term

variability in active layer depth requires measurements of permafrost tem-
SEARCH Large-Scale Observations Workshop 45

a

b

Figure 4.5: (a) Candidate boreholes for permafrost thermal monitoring (provided by V. Romanovsky, University of Alaska Fairbanks) and (b) Glacier mass balance locations in the Arctic (from Jania and Hagen,

1996). Black circles indicate glaciers with more than 20 years of observations, and empty circles indicate

glaciers with between 5 and 20 years of observations. 1–Wolverine Glacier, 2–Gulkana Glacier, 3–Melville

S. Ice Cap, 4–Melville W. Ice Cap, 5–Melville E. Ice Cap, 6–Leopold Glacier, 7–Meighen Ice Cap, 8–White

Glacier, 9–Baby Glacier, 10–Ward Hunt Ice Shelf, 11–Ward hunt Ice Rise, 12–Per Ardua Glacier, 13–Gilman

Glacier, 14–Agassiz Glacier, 15–Laika Glacier, 16–Laika Ice Cap, 17–Devon Ice Cap, 18–Barnes Ice Cap,

19–Decade Glacier, 20–Boas Glacier, 21–Satujokull, 22–Qamanarssup sermina, 23–Konsvegen, 24–Austre

Brogerbreen, 25–Midre Lovenbreen, 26–Voringbreen, 27–Bertilbreen, 28–Hansbreen, 29–Storglaciaren, 30–

Engabreen, 31–IGAN Glacier, 32–Obruchev Glacier, 33–Vavilov Glacier.
46 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

peratures for interpretation. Measurements of active layer at the borehole

sites may provide the capability to observe and interpret long-term changes

in active layer depth. The International Permafrost Association is implementing the Global Terrestrial Network for Permafrost (GTN-P) for the

WMO/ICSU Global Climate Observing System (GCOS) and Global Terrestrial Observing System (GTOS). Northern hemisphere CALM sites (80 in

number, http://www.geography.uc.edu/%7Ekenhinke/CALM/map.html)

and nine European permafrost boreholes from the Permafrost and Climate in

Europe program (http://www.cf.ac.uk/earth/pace/fieldsites/index.

html) are currently part of GTN-P.

Freeze-thaw dynamics in high latitude regions are intimately tied to

changes in growing season length, and have substantial implications for the

exchange of water, energy, and trace gases with the atmosphere and influences hydrology. NSIDC currently provides a land-based freezing/thawing

degree-day product based on climatology station records, but it does not

provide adequate resolution or coverage of the polar regions, particularly in

mountainous terrain. Also, it is not clear whether this product has been adequately validated for regions of continuous and discontinuous permafrost.

Analyses based on data from NASA scatterometers (NSCAT, SeaWinds)

show some promise for monitoring the freeze-thaw status of the land mass

(Rignot and Way, 1994; Running et al., 1999a; Frolking et al., 1999), but the

algorithms and technology need further evaluation and development as the

scatterometers are not formally optimized for land-based cryospheric applications. It may also be possible to detect onset of surface melt from changes

in surface microwave emissivity, which would go from relatively high emissivities when the surface is frozen to low values when the surface has standing

water. A cold-processes satellite mission that has been proposed to NASA

is focused on measuring changes in freeze-thaw dynamics and may provide

the ability to monitor changes in freeze dynamics across high latitudes if the

mission becomes a reality. The suggested borehole network would provide

the capability to monitor systematic changes in freeze-thaw dynamics that

could be valuable in validating climatological and remote sensing algorithms

of freeze-thaw dynamics.

While the International Permafrost Association has put together a map

of permafrost extent (International Permafrost Association’s circumarctic

map, published 1997, http://www.grida.no/prog/polar/ipa/), the map

is primarily of interpretive value as the resolution is coarse and it is not useful

for assessing changes in permafrost extent. The mapping of permafrost in

a spatially explicit fashion is a major challenge to the scientific community

that requires new approaches. There are several remote sensing technologies

that might be brought to bear on monitoring thermokarst topography, which

would aid in understanding changes in permafrost extent. In particular, the

cold-processes satellite mission that has been proposed to NASA may provide

some improved technical capabilities to map permafrost extent.
SEARCH Large-Scale Observations Workshop 47

4.4.4 Glaciers and Ice Sheets

A key issue of high-latitude glaciers and ice sheets relevant to the Arctic

System is whether ice mass is changing. Below we first discuss the monitoring

of ice mass changes in the Greenland Ice Sheet and then discuss changes of

ice mass in glaciers.

In spite of their poor temporal coverage, existing data sets from radar

altimetry (Seasat, Geosat, ERS) provide a picture of change in the high interior of the Greenland Ice Sheet over the last few decades; this data stream

continues but is not of use near the ice margins, where the most rapid variations occur. NASA airborne laser measurements have identified significant

changes in the Greenland Ice Sheet over the last half of the 1990s, a result

that has provided the first definitive measurement of one ice sheet’s contributions to the present rate of sea level rise. The proposed ICESat NASA

mission has the potential to provide systematic coverage of the Greenland

Ice Sheet and, based on the aircraft results, would allow the first comprehensive assessment of the present contribution of the ice sheet to sea level

rise. Note that extended time series of these measurements are necessary

to understand the background variability of the processes which determine

surface elevation, and provide the opportunity to assess the causes of change,

which is required to develop a predictive understanding of ice sheet variations. Also required are data on accumulation rates and variations, melt

rates, and changes in ice flow.

Elsewhere across the Arctic, the smaller glaciers have exhibited a mixed

response to recent climate fluctuations. Syntheses of available data by Jania and Hagen (1996) and Dowdswell et al. (1997) indicate that ice mass

of Arctic glaciers has been generally decreasing in recent decades, except in

Scandinavia, where ice mass is increasing as a result of shifting atmospheric

circulation patterns that have produced greater winter precipitation. There

are numerous glaciers across the Arctic which have been part of long-term

mass balance measurement programs (Fig. 4.5b). For example, the USGS

has measured the seasonal mass balance of two glaciers in Alaska for more

than 40 years. However, the number of glaciers under scrutiny has drastically declined as a result of declining interest by their respective funding

sources. Haberli (2001) summarizes the global mass balance observations,

and a comparison with the observations described in Jacek (1996) clearly

shows the dramatic reduction in observations.

It is unlikely that interest in glacier mass balance measurements will increase to yield re-establishment of abandoned programs. Furthermore, these

programs were man-power intensive and provided information from only a

relative handful of glaciers. New capabilities in remote sensing, both satellite

and aircraft, can observe Arctic glaciers on a routine basis and provide glacier

fluctuation information, as is being carried out over Greenland. The USGS

led GLIMS project is developing techniques to provide glacier information

from ASTER observations. Other satellite data sources include LANDSAT

7, and the approximately 1 m resolution imagery from IKONOS and Quickbird. While imagery from the later two sensors is expensive, they are the

harbingers of future hi-resolution imagery, and efforts should be undertaken
48 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

to develop techniques that take full advantage of these capabilities. Future

Arctic glacier observations should, where possible, be made on glaciers that

have an existing record of mass balance observations.

The World Glacier Monitoring Service is implementing the Global Terrestrial Network for Glaciers (GTN-G) for the WMO-ICSU Global Climate

System (GCOS) and Global Terrestrial Observing System (GTOS). It consists of 60 glaciers from all of the world’s major mountain ranges that are

Tier 2 (with intensive research and observation activities) and Tier 3 (with

annual mass balance studies) sites.

4.4.5 Lakes and Wetlands

Key issues of lakes and wetlands include changes in lake temperature, lake

chemistry, break-up/freeze-up dates, ice thickness, lake area, and wetland expansion/

contraction.

Data presented from long-term monitoring of Toolik Lake in Alaska indicates that the lake has warmed substantially over the past 25 years and

that the lake chemistry has become more alkaline.

Break-up and freeze-up dates of lakes are a good proxy for climate change

and can be estimated via in situ and remote sensing observations. There are

currently substantial limitations to using remote sensing. For example, while

ERS 1/2 is quite useful for detecting frozen vs. thawed lakes, the temporal

frequency is not good enough to precisely determine break-up and freeze-up

dates. Products with daily temporal frequency, e.g., the AVHRR 1.25 km

and 5 km resolution path finder (since 1982) and OLS on DMSP have the

potential to be used to produce a record of break and freeze up over medium

to large lakes. Thus, satellite remote sensing of break-up and freeze-up dates

is currently a research and development activity rather than an operational

activity.

Analyses of in situ observations suggest that lakes in North America

are generally breaking up earlier (Magnusson et al., 2000), although there

are regional differences in trends. For example, in Canada the length of

the ice-free season has increased in some areas and decreased in others.

NSIDC maintains the LIAG database, which contains information for 270

lakes above 55◦N, 155 of which are from Canada. Only about 20 of the lakes

in the database have records that are older than 20 years. For some lakes,

ice thickness is also measured. There is a need to rescue Russian data that

has been collected on the timing of break-up and freeze-up. There is some

limited evidence from historical photographs and Landsat imagery that low

elevation lakes in Alaska and Yukon, specifically on the Seward Peninsula, in

the Copper River Valley, and in Old Crow Flats are shrinking in size while

lakes at higher elevation are not changing in area. It is not entirely clear if

these observations represent interannual variability or represent longer-term

trends. Remote sensing studies are currently being conducted to determine

if this is a regional phenomenon that may be caused by greater drainage

associated with permafrost degradation. There is also evidence of substantial
SEARCH Large-Scale Observations Workshop 49

thermokarst development in the Tanana Flats near Fairbanks that may be

leading to more open water in those wetlands (Osterkamp et al., 2000).

4.4.6 Hydrology

Key parameters relevant to terrestrial hydrology include precipitation, evapotranspiration, soil moisture, and river discharge.

Although there are many conventional data sets for precipitation, they do

not provide adequate coverage of high latitude and polar regions. Global precipitation data sets combining satellite and ground-based data are currently

available from other agencies such as the WMO Global Precipitation Climatology Center and the Global Precipitation Climatology Project (GPCP).

For Arctic applications, NSIDC maintains historical archives of land-station

precipitation from the former Soviet Union and Canada. The observations

in these data sets are available with corrections for gauge biases, the most

severe of which is associated with the undercatch of snowfall. As different

countries use different gauges, and the bias in the gauges depend on a lot

of factors (e.g., wind speed), the correction for biases present in large-scale

precipitation data sets is a difficult problem, and while corrections can be

made, large errors remain.

Evapotranspiration fields currently must be estimated with a model.

The simplest, so-called reference surface techniques require but mean daily

temperature while more physically based functions, typically employed in

soil-vegetation-atmosphere-transfer schemes and process-based studies, can

require skin temperature, humidity, net radiation, aerodynamic roughness,

albedo, leaf area index, and wind speed. While several, but not all, of these

required input variables or parameters are measured routinely by satellites,

there are very few sites where most of these variables are simultaneously

measured on the ground. Vegetative properties such as leaf area index and

land cover are also essential. Variables such as wind speed, temperature, humidity, and pressure data over polar land areas are obtained from rawinsonde

observational networks and are archived at NSIDC. Coarse-resolution data

sets for evapotranspiration are currently available from the National Center

for Environmental Prediction (NCEP) and European Center for Mediumrange Weather Forecasting (ECMWF) operational and re-analysis activities. Validation over grid-cell areas is needed in order to provide a basis for

improved parameterizations of evapotranspiration in future reanalyses.

Passive microwave radiometers have been used to detect soil moisture.

Systems such as SSM/I or AMSR have the advantage of acquiring this information on a routine basis (few days re-visit time) from space with a resolution on the order of 50 km or larger. However, interference from vegetation

limits to what can usefully be obtained from these sensors at this time. The

Global Soil Wetness Project uses AVHRR-derived vegetation information

and modeling to produce global soil moisture fields, but these fields have

not been adequately evaluated for high-latitude regions. A proposed NASA

post-2002 mission to monitor soil moisture at 10 km resolution is currently
50 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

under consideration. Higher resolution SAR data has also been shown to

provide some information about soil moisture.

River discharge must typically be obtained from ground-based station

data available through several archives. Major subsets of these holdings

have been organized into a pan-Arctic data collection, and the NSF-ARCSS

funded Arctic-RIMS project is operationally monitoring near-real time river

discharge information for river systems in the pan-Arctic drainage basin.

Analyses of available data by Serreze et al. (2002), Yang et al. (2002) and Peterson and Holmes (personal communication) indicate that (1) annual water

discharge is increasing for major rivers of the Eurasian plate (Yenisey, Lena,

and Ob), but not for major rivers of the North American plate (Mackenzie,

Yukon, Kolyma), (2) cold season discharge is increasing in the Yenisey and

Lena drainages, (3) and that the discharge of the Yenisey has increased in

the spring and decreased in the summer. These changes in the Yenisey appear to be related to higher air temperature, increased winter precipitation,

and summer drying and may be additionally linked to changes in active layer

thickness and to the thawing of permafrost. At a time when the analyses

of historical data on river discharge are starting to yield substantial insights

as to the effects of changes in the Arctic System, it is disconcerting that the

number of monitoring stations has been dropping in recent decades (Shiklomanov and V ̈or ̈osmarty, 2002). Major needs are to retard or reverse the

degradation of the network of monitoring stations and to rescue Russian

data that is not currently available in pan-Arctic and global archives.

While river discharge is the integrated response of a river catchment,

the processes affecting discharge are so many and so complex that it may

be difficult to invert information on variability and trends in river discharge

to infer the changes in hydrologic processes that are responsible for dynamics of river discharge. Although additional gauging stations are needed to

understand regional and global water balance, monitoring discharge alone

will not enable attribution of changes in the hydrologic cycle to their causes.

Thus, river discharge data will be of greatest value when accompanied by

complementary meteorological data that permits complete water and energy balance analyses. A coordinated set of research basins, all monitoring

snow distribution, snow melt, energy balance, soil moisture dynamics, runoff,

evaporation, transpiration and sublimation with complementary techniques

is needed to adequately characterize pan-Arctic changes in water and energy cycles. Such complete data sets are not collected operationally by any

agency, but are currently being assembled in a very small number of research

watersheds in the Arctic. These comprehensive research sites are characteristically of short duration with little or no long-term stability. Also, winter

measurements frequently suffer because of harsh conditions combined with

remote access, but can be improved with real-time telemetry monitoring.

These stations should be supported and the technology improved to provide

reliable year-round operation.
SEARCH Large-Scale Observations Workshop 51

4.4.7 Trace Gas Exchanges

Key terrestrial parameters related to trace gas exchanges of high latitude terrestrial ecosystems with the atmosphere include carbon dioxide flux, methane

flux, and the lateral transport, processing, and delivery of dissolved organic

carbon (DOC) to surface hydrologic networks and the oceans.

There are two general modeling methods for assessing changes in the

exchange of carbon dioxide between high-latitude terrestrial ecosystems and

the atmosphere: (1) inverse modeling and (2) forward modeling. Inverse

modeling is generally based on methodologies that use atmospheric CO2

concentrations that have been observed at stations as part of the global

CO2 monitoring network; many of these stations are maintained by NOAA

CMDL. In contrast, forward modeling uses process-based models that have

been developed in the context of observations and process studies to simulate

the exchange of carbon dioxide for large regions. Analyses based on inverse

modeling suggest that during the 1980s northern high latitude ecosystems

have released carbon while southern high latitude ecosystems have stored

carbon (Kaminski et al., 1999). The release of carbon by northern high latitude ecosystems appears to have been strongest in the late 1980s (Kaminski

et al., 1999), which is consistent with a synthesis of carbon studies for northern Alaska over the last two decades (Oechel et al., 2000). Studies that have

examined the confidence of inversion estimates in northern Europe, northern

Asia, and northern North America have identified substantial interannual

variability in the exchange of carbon dioxide for all regions (Dargaville et

al., 2002). There are large uncertainties in the inversion estimates because

the methodology is not fully constrained and assumptions must be made to

provide constraints that lead to a solution. Examination of the uncertainties associated with the assumptions than need to be made indicate that

inversion estimates are much better constrained for northern North America

than for northern Europe and northern Asia (Dargaville et al., 2002). One

forward modeling analysis for northern North America over the last two

decades (McGuire et al., unpublished) shows similar interannual variability

in the net flux as the inversion analysis of Dargaville et al. (2002). The forward modeling analysis also identified that fire was the key issue responsible

for the match of inter-annual variability between the forward and inverse

estimates. Other studies indicate that regional changes in the fire regime,

i.e., whether fire becomes more frequent or less frequent, primarily determine

whether the region is a source or sink for carbon over the last several decades

(McGuire et al., unpublished). The nature of the fire regime also appears

to play a role in patterns of vegetation carbon turnover between northern

North America and northern Asia as ground fires in northern Asia lead to

longer turnover in comparison to crown fires in North America (McGuire et

al., 2002). With respect to long-term changes in soil carbon storage in high

latitude ecosystems, a key uncertainty appears to be associated with limited

understanding about the turnover of soil carbon in high latitude ecosystems

(Clein et al., 2000, 2002; McGuire et al., 2002).

In comparison to carbon dioxide, both inverse and forward modeling of

methane for high-latitude regions is substantially lagging primarily because
52 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

the availability of data for developing these models is much more limited in

comparison to carbon dioxide. With respect to inverse modeling, the atmospheric chemistry of methane, which is more complex than the atmospheric

chemistry of carbon dioxide, must also be considered.

Limitations on the understanding of patterns and controls over carbon

dioxide and methane exchange with the atmosphere in high-latitude regions

is primarily associated with limited data availability on variability in these

fluxes and on controls over that variability. New technologies that rely on

measuring the vertical structure of trace gases in the atmosphere are currently being deployed to document the spatial and temporal variability of

trace gas fluxes. Tall eddy covariance towers and continental scale aircraft

campaigns, both of which are now being initiated in Siberia with support

from the European Union and the Max Planck Institute for Biogeochemistry,

are designed to improve the spatial resolution of flux estimates in comparison

to extant inversion techniques. SEARCH should consider to what extent it

can augment and enhance these campaigns. At finer spatial scales (hectare

to km2), networks of eddy covariance sites are just beginning to provide insight concerning the spatial and temporal variability of trace gas, water, and

energy fluxes (Baldocchi et al., 2001; Running et al., 1999b). For tundra in

northern Alaska, eddy covariance sites have provided essential information

during the 1990s for evaluating decadal-scale trends in summer carbon exchange with the atmosphere (Oechel et al., 2000). A network of these sites

now exists around the pan-Arctic which provides the capability to compare

observations with estimates based on remote sensing (Fig. 4.6a) and process modeling (Fig. 4.6b). However, the collection of data at individual sites

in this network is not operationally supported by any agency, but is maintained by research grant to a small number of investigators throughout the

Arctic. Because these research sites have little or no long-term stability, they

are vulnerable to the vagaries of funding. Also, similar to hydrologic measurements, winter measurements at eddy covariance sites frequently suffer

because of harsh conditions combined with remote access. SEARCH should

consider to what extent it can support operation of some of these sites along

with associated process studies to better understand controls, particularly

as these sites provide simultaneous information on the exchanges of trace

gases, water vapor, and energy with the atmosphere.

The lateral transport and processing of DOC in freshwater systems to

the oceans is important because it represents terrestrial carbon that may

influence the exchange of trace gases between the atmosphere and aquatic

ecosystems, both in freshwater and in the coastal zone (Kling et al., 1991;

Schlesinger et al., 1991; Stallard et al., 1998). This may be especially important in the Arctic because of the organic rich soils that are the source of

DOC to aquatic ecosystems, which may be sources of CO2 and methane to

the atmosphere (Reeburgh et al., 1998). While DOC has been measured at

the mouth of some of the major river systems, different methods of measuring DOC make comparisons difficult. Also, lateral transport and processing

of DOC in rivers of the pan-Arctic Drainage Basin are incompletely understood. The USGS is just initiating a 5-year program to document the lateral

transport of DOC and other constituents in the Yukon River. The transport
SEARCH Large-Scale Observations Workshop 53

a 

NEP g C/m2/yr

CO2 Monitoring Site

CO2 + CH4 Monitoring Site

–60 – –50

–50 – –40

–40 – –30

–30 – –20

–20 – –10

–10 – 0

0 – 10

10 – 20

20 – 30

30 – 40

40 – 50

b

Figure 4.6: Locations of sites monitoring exchanges of carbon dioxide and methane between high latitude

terrestrial ecosystems and the atmosphere (compilation of sites provided by W. Oechel of San Diego State

University and T. Christensen, University of Lund). Fluxes measured at these sites have the potential to be

compared with estimates based on (a) remote sensing (estimates courtesy of Steve Running, University of

Montana) and (b) process modeling (NEP estimates for 1985–1994 from McGuire et al. 2000b).
54 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

and processing of DOC near the Siberian coast of the Arctic Ocean is also

a focus of several RAISE studies funded by NSF ARCSS. There is a need

to assess the quality of extant data that have been archived and to rescue

data that have not been archived into an operational pan-Arctic data base

of DOC and other constituents.

4.5 References

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SEARCH Large-Scale Observations Workshop 55

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SEARCH Large-Scale Observations Workshop 59

5. Sea Ice Observations

Compiled by Jackie Richter-Menge with contributions from Don Cavalieri,

Greg Holloway, Ron Lindsay, Ola Perrson, and Ignatius Rigor.

Rapporteurs: Bonnie Light and Florence Fetter

5.1 Introduction

During this session of the workshop, participants were asked to focus on issues associated with the design of a large-scale observing system to monitor

variations in the sea ice cover that can be used as indicators of environmental change. Selecting this particular focus was not meant to diminish the

importance of conducting investigations to improve the fundamental understanding of climate change. In fact, workshop participants acknowledged

that studies designed to better understand dynamic and thermodynamic

processes that govern energy exchange are critical for the development of

predictive capabilities.

Focusing on the development of a large-scale observing system did allow

participants to make considerable headway toward meeting the objectives

of the workshop. The session began with brief presentations by each panel

member, describing their perspective on important issues associated with relevant sea ice observations. A summary of these presentations can be found

in the workshop notes, included on the workshop’s web page. With this

foundation, the floor was opened for discussion. The first part of the discussion was spent identifying key measurement parameters. Participants, then,

qualitatively established a relative sense of the current level of confidence

in measuring these parameters and discussed the available methods. Recognizing the particular importance of monitoring the sea ice thickness and the

particularly high degree of difficulty in doing so, a significant amount of time

was devoted to this specific topic. Based on the discussion, recommendations

are made for immediate efforts that should be undertaken to more effectively

exploit the sea ice cover as a tool for monitoring the environmental change

in the Arctic.

5.2 Recommendations

It is important that efforts be made to continue to develop our capabilities to

accurately measure the components that contribute to the distributed mass

balance of the sea ice cover. These components include the sea ice extent, the

dynamic and thermodynamically driven redistribution of the sea ice cover,

the export of sea ice from the Arctic Basin, and the thickness of the sea ice

cover, including the overlying snow cover. However, it is recommended that

efforts to accurately measure the thickness of the sea ice cover, including

overlying snow cover, be given the highest research priority. This recognizes

the significant importance of measuring the thickness of the sea ice cover and

the associated lack of confidence in the ability to do so at an accuracy and

scale appropriate for a large-scale observing system. Specifically, we need to

continue, improve, and expand current measurement techniques:
60 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

 Submarine transects should be continued, repeating measurements

along identified transects to provide a historical record.  Moored upward-looking sonar (ULS) should be deployed in a more

systematic fashion to provide information on decadal and interannual

variability.  Previously obtained data from moored ULS should be made available

to the scientific community, using a coordinated archival system.  Instruments to measure ice thickness and snow depth (e.g., thermistor

strings and acoustic range finders) should be added to surface-deployed

drifting buoy stations.  Sea ice models, coupled with recorded direct observations, should be

used to optimize a deployment strategy for moored ULS and instrument-enhanced drifting buoys.  A regional study should be conducted to develop and validate aircraft

and satellite-derived snow and ice thickness measurements.

5.3 Background

As pointed out in the SEARCH Science Plan (SEARCH SSC, 2001), the sea

ice cover is a critical component of the Arctic environment, largely controlling the energy exchange between the atmosphere and ocean. It is further

emphasized in the SEARCH Science Plan that understanding the state of

the sea ice cover is critical to all of the objectives of SEARCH. In addition

to playing a key role in the surface energy balance, the sea ice cover appears to be a sensitive indicator of changes in the global circulation system.

Both the extent and the thickness distribution of the sea ice cover respond

quite dramatically to changes in the heat and momentum of the atmosphere

and ocean. The thickness distribution in a given region is controlled by

thermodynamic growth and decay, ice motion (advection), and mechanical

redistribution. The state of the sea ice cover represents the integrated effects

of atmospheric and oceanic forcing.

The sensitivity of the sea ice cover to changes in the global circulation

system is well demonstrated in a recent paper by Kwok (2000). Kwok uses

satellite data and measurements from drifting buoys to establish a new ice

motion dataset of the Arctic Ocean for the winters from 1978 through 1996.

Using this dataset, it is shown that patterns of variability in the sea ice cover

can be directly linked to the North Atlantic Oscillation (NAO). It is specifically demonstrated that changes in the dominant mode of the NAO affect

the ice motion, ice flux, and ice extent. Kwok’s results are consistent with

the modeling results of Proshutinsky and Johnson (1997), who report two

dominant regimes of wind-forced circulation, affecting the ice motion over

the 48-year study period, from 1946–1993. As Kwok suggests, it appears

that the circulation patterns in the positive NAO (NAO+) and negative

NAO (NAO–) regimes are respectively similar to the cyclonic and anticyclonic regimes identified by Proshutinsky and Johnson. During periods of
SEARCH Large-Scale Observations Workshop 61

NAO > 1

0 < NAO ≤ 1

 –1 < NAO ≤ 0

NAO ≤ –1

a

b

c

d

Figure 5.1: Composite patterns of monthly (October through May) sea-level pressure and ice motion fields

between 1978 and 1996 partitioned based on the monthly NAO index. (a) NAO >1. (b) 0 < NAO ≤ 1. (c)

–1 < NAO ≤ 0. (d) NAO ≤ –1. The contour increment is 1 hPa (from Kwok, 2000).
62 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

NAO+ or cyclonic circulation, both the Beaufort Gyre and the Transpolar Drift Stream weaken and the Transpolar Drift Stream shifts westward

towards the Canada Basin (Fig. 5.1). Further consistent evidence of the

sensitivity of the sea ice cover to changes in the global circulation system is

provided by Tucker et al. (2001), who present an 8-year time series of sea ice

thickness, derived from submarine-based upward looking sonar. This work

shows that rapid thinning of the ice in the Canada Basin occurred in the late

1980s, coincident with a shift in the Arctic Oscillation (AO), which is closely

related to the NAO, to AO+, and increased advection from the Arctic Basin.

The fact that variations in the ice circulation pattern and, hence, state of

the ice cover is strongly linked to changes in atmospheric forcing comes as no

surprise. It has been well established by Thorndike and Colony (1982) that,

away from coastal boundaries, the geostrophic wind explains more than 70%

of the variance of daily ice motion in both winter and summer.

5.4 Key Parameters and Current Measurement Techniques

Given the sensitivity of the sea ice cover to variations in the global circulation system, the focus of this workshop session was to consider how to best

exploit the sea ice cover for monitoring environmental change in the Arctic

region. Participants unanimously agreed that the key parameter to monitor,

to detect change in the climate system, is the distributed mass balance of

the sea ice cover. The task of determining the distributed mass balance can

be broken into four main components, listed below. The current relative

level of confidence in quantitatively determining each of these parameters

is represented by the order of this list, with the measurement of ice extent

having the highest level of confidence:  Measuring the extent of the ice cover,  Establishing the redistribution of the ice cover, resulting from thermodynamic and dynamic processes,  Measuring the export of ice from the Arctic Basin, and  Determining the snow and ice thickness, including open water and thin

ice fractions.

5.4.1 Ice extent

The level of confidence in measuring ice extent significantly exceeds that

of the other three components. This is due, in large part, to the ability

to effectively apply satellite imagery, specifically passive microwave data, to

distinguish the boundary between the ice-covered and open ocean regions,

throughout the year (e.g., Parkinson et al., 1999). The satellite platform

has the distinct advantage of providing a bird’s eye view of the entire sea

ice cover. It was suggested that particular regions of the Arctic ice cover

could be selected for monitoring changes in the sea ice extent, as a function

of environmental forcing conditions. These regions would be selected based

on their demonstrated sensitivity to environmental change and the existence
SEARCH Large-Scale Observations Workshop 63

of a relatively long historical record. A good example of a region that meets

these criteria is the Sea of Okhotsk (Cavalieri and Parkinson, 2001).

5.4.2 Redistribution

Redistribution means the changes in the thickness distribution of the sea

ice cover that occur due to both dynamic (advection, lead formation, ridge

formation) and thermodynamic (ice growth and melt) processes. Currently,

sea ice dynamic-thermodynamic models are a primary tool used to establish the redistribution of the ice cover (e.g., Zhang and Rothrock, 2001).

There are a variety of sea ice models available for this analysis, each with

a distinguishing set of assumptions and governing equations. Typically, the

accuracy of a model is established by comparing model results of ice motion

to the movement of drifting buoys, installed in the sea ice cover. Recent

overviews provide a detailed perspective on the status of sea-ice models and

model development (e.g., Randall et al., 1998; Steele and Flato, 2000).

Ideally, direct measurements of the redistribution at appropriate spatial

and temporal scales should be used in tandem with the models. Making such

direct measurements has proven to be a very difficult challenge. However,

recent examples of the application of data from the RADARSAT Geophysical

Processor System (RGPS), derived from SAR imagery, show the potential

in applying satellite imagery to this issue (e.g., Kwok, 1998; Stern et al.,

1995).

5.4.3 Export

Estimates of the volume of ice exported from the Arctic Basin, which primarily occurs through the Fram Strait, can be made with moored upward

looking sonar (ULS) (Vinje et al., 1998). Submarine-based ULS have also

been used for this purpose (Wadhams, 1983). Satellite passive microwave

data can be used to estimate the area of ice exported through the Fram

Strait during the winter (Kwok and Rothrock, 1999). This is accomplished

by tracking the displacement of common features in sequential images, to

determine ice motion.

5.4.4 Ice thickness and snow depth

The most difficult parameter to measure represents the most important parameter to monitor: the thickness of the sea ice cover. Throughout this section, when the thickness of the sea ice cover is mentioned, it is intended that,

whenever possible, any overlying snow cover also be measured. As explained

in a background summary “Sea Ice Thickness: The Great Integrator”, prepared for this workshop and available on the workshop’s web page (http://

www.epic.noaa.gov/SEARCH/obs/workshop/reports.shtml), there are a

variety of techniques used to measure or derive the ice thickness:  Moored upward looking sonar (ULS) (e.g., Melling et al., 1995)  Submarine-based ULS (e.g., Tucker et al., 2001; Rothrock et al., 1999;

Wadhams and Davis, 2000)
64 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

 Aircraft-based altimeters (e.g., Wadhams et al., 1992)  RGPS (e.g., Kwok et al., 1999)  Buoys with thermistor strings (e.g., Perovich et al., 1997)

Of these techniques, buoys with thermistor strings can also be used as

an autonomous means of monitoring snow depth. Satellite microwave radiometers have been used in the Antarctic to derive the snow depth on sea

ice (e.g., Markus and Cavalieri, 1998).

To date, the only technique that has provided the scientific community

with a historical perspective, adequate to investigate the relationship between the ice thickness and environmental conditions, is the submarine-based

upward looking sonar. Specifically, considerable data have been made available in the western, central, and eastern Arctic. Concerns have been raised

regarding the impact of the limited regional sampling of the submarine data

on the conclusions drawn from this data source. This limitation is due to

the lack of submarine visits to all locations within the Arctic Basin and

restrictions associated with data release.

To make more effective use of moored-upward looking sonar and instrument-enhanced drifting buoys, it was suggested that sea ice models, combined with recorded observations, be used to design a deployment strategy.

Analyses can be done to identify locations of dominant modes of variation,

related to environmental change, or good locations for measuring the annual

variation in mean ice thickness. Associated studies can be conducted to determine the optimal location and number of instrumented sites within these

regions.

Since the conclusion of the workshop, Ron Lindsay, at the University

of Washington Applied Physics Laboratory, has applied the sea ice model

described in Zhang and Rothrock (2001) to provide an example of how such

an exercise could be carried out (Fig. 5.2). First, the sea ice model was used

to create a 48-year time series of the basin-wide, annual mean ice thickness

(Fig. 5.2a). Next, each model grid point was correlated with the basin-wide,

annual mean ice thickness, to establish the optimal location for measuring

the mean thickness of the sea ice cover. The results of this analysis are

presented in Fig. 5.2b, where contours of R2 are plotted. These results

suggest that if, for instance, a moored ULS was located at a point between

Canada and the North Pole it would explain 79% of the variance of the mean

ice thickness, described by a linear fit to the thickness in this region. Fig. 5.2c

illustrates the additional explained variance of the mean ice thickness gained

by establishing two measurement sites, one at the North Pole and a second

in the Chukchi Sea. With data from these combined sites, the explained

variance in the mean ice thickness increases to 86%. An autocorrelation of

the ice thickness at the North Pole (Fig. 5.2d) determines the fraction of the

variance at each grid point explained by the time series of the ice thickness

at the North Pole. This result suggests that the regional variability of the ice

thickness is not well predicted by just one measurement site point between

Canada and the North Pole.
SEARCH Large-Scale Observations Workshop 65

Figure 5.2: Example of the application of a sea ice model in the design of a large-scale observing system

for the sea ice cover. Here, correlation analyses are used to determine the optimum location of moored

upward-looking sonars (provided by Ron Lindsay).

Lindsay provides another example of the application of model results, to

assist in the design of a large-scale sea ice observing system (Fig. 5.3). Here,

the model described in Zhang and Rothrock (2001) is used to determine

the difference in the mean ice thickness distribution between two dominant

forcing regimes. In Fig. 5.3a, these two regimes are defined according to

the work of Proshutinsky and Johnson (1997), who separated the years from

1946 to 1993 into one of two dominant wind-driven regimes; cyclonic or

anticyclonic. In Fig. 5.3b, the same years are separated into categories using the positive and negative AO index, as defined by David Thompson at

http://www.atmos.colostate.edu/ao/Data/ao index.html. In each approach, the number of years in the two categories was nearly equal, although

they were not necessarily the same years. While there are subtle differences

between these two results, the agreement is more remarkable. Both confirm

that the North Pole is a location of low variability in mean ice thickness. This

result is consistent with conclusions drawn from submarine-upward looking
66 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

Figure 5.3: Example of the application of a sea ice model in the design of a large-scale observing system for

the sea ice cover. Here, the level of variability in the mean ice thickness is established by comparing model

results between two dominant types of atmospheric forcing (provided by Ron Lindsay).

sonar data, as reported in McLaren et al. (1994), Shy and Walsh (1999), and

Tucker et al. (2001). Tucker et al. speculate that the location of the North

Pole in a strongly advective region for both atmospheric forcing regimes is

responsible for the low temporal variability in the ice thickness at the North

Pole. The Canadian sector of the Beaufort Sea and the East Siberian and

Laptev Seas are regions of high interannual variability in mean ice thickness.

The results from Lindsay’s work are presented as an example of how the

scientific community can apply established sea ice models to assist in the

design of a large-scale sea ice observing system. If it was determined that

such a course of action would benefit the objectives of SEARCH, it should

be recognized that different sea ice models are likely to give different results.

This is a consequence of the variety of fundamental assumptions made in

the development of individual models. Given this expected variability, it is

suggested that results from a number of selected models should be used in

the design phase of the observing system. These results should be compared

to determine the deployment locations most consistently indicated by the

models. Direct observations and measurements of the characteristics of the

sea ice cover should be coupled with the combined model results to provide

an even greater degree of confidence in the design strategy.

All of the measurement techniques currently available to monitor the

ice thickness are inherently limited, since they offer observations from specific locations within the Arctic Basin. Many also pose significant logistical

challenges. Given the current capabilities of various satellite systems, developing these platforms into a tool that provides reliable information on

snow and ice thickness would require investigations to develop and validate

satellite-derived data (Walsh et al., 2001). This can be done by a regional

study, where currently available measurement systems are used in a hierarchical fashion. For instance, an array of moored upward-looking sonars
SEARCH Large-Scale Observations Workshop 67

and drifting buoys, instrumented with thermistor strings, could be deployed

in a selected test region, to provide Eulerian and Lagrangian time series of

ice thickness, respectively. Surface-based transects to measure the snow and

ice thickness and important physical properties could be conducted in the

same region at critical times. Aircraft equipped with altimeters, and submarines equipped with upward-looking sonar, could also survey the region.

This suite of measurements of snow and ice thickness would be compared to

the results obtained from satellites, imaging the defined study region.

5.5 References

Cavalieri, D.J., and C.L. Parkinson (2001): Sea ice variability in the Seas of Okhotsk

and Japan from passive microwave satellite observations. In Proceedings of the

International Symposium on Atmosphere-Ocean-Cryosphere Interaction in the

Sea of Okhotsk and the Surrounding Environment, M. Wakatsuchi and T. Hara

(eds.), 12–15 December 2000, Sapporo, Japan, 28–29.

Kwok, R. (2000): Recent changes in the Arctic Ocean sea ice motion associated

with the North Atlantic Oscillation. Geophys. Res. Lett., 27, 775–778.

Kwok, R. (1998): The RADARSAT Geophysical Processor System. In Analysis of

SAR data of the Polar Oceans: Recent Advances, C. Tsatsoulis and R. Kwok

(eds.), Springer-Verlag, New York, 235–258.

Kwok, R., and D.A. Rothrock (1999): Variability of Fram Strait ice flux and North

Atlantic Oscillation. J. Geophys. Res., 104, 5177–5189.

Kwok, R., G.F. Cunnigham, N. LaBelle-Hamer, B. Holt, and D. Rothrock (1999):

Ice thickness derived from high-resolution radar imagery. Eos, Trans. AGU, 80,

495, 497.

Markus, T., and D.J. Cavalieri (1998): Snow depth distribution over sea ice in

the Southern Ocean from satellite passive microwave data. In Antarctic Sea

Ice: Physical Processes, Interactions and Variability, Antarctic Research Series,

Volume 74, American Geophysical Union, Washington, D.C., 19–39.

McLaren, A.S., R.H. Bourke, J.E. Walsh, and R.L. Weaver (1994): Variability

in sea-ice thickness over the North Pole from 1958 to 1992. In Polar Oceans

and Their Role in Shaping the Global Environment, O.M. Johannessen, R.D.

Muench, and J.E. Overland (eds.), American Geophysical Union, 373–371.

Melling, H., P.H. Johnston, and D.A. Riedel (1995): Measurements of the underside

of sea ice by moored subsea sonar. J. Atmos. Oceanic Tech., 12, 589–602.

Parkinson, C.L., D.J. Cavalieri, P. Gloersen, H.J. Zwally, and J.C. Comiso (1999):

Arctic sea ice extent, areas, and trends. J. Geophys. Res., 104, 20,837–20,856.

Perovich, D.K., B.C. Elder, and J.A. Richter-Menge (1997): Observations of the

annual cycle of sea ice temperature and mass balance. Geophys. Res. Lett., 24,

555–558.

Proshutinsky, A.Y., and M.A. Johnson (1997): Two circulation regimes of the winddriven Arctic Ocean. J. Geophys. Res., 102, 12,493–12,514.

Randall, D., J. Curry, D. Battisti, G. Flato, R. Grumbine, S. Hakkinen, D. Martinson, R. Preller, J. Walsh, and J. Weatherly (1998): Status of and outlook for

large-scale modeling of atmosphere-ice-ocean interactions in the Arctic. Bull.

Am. Meteorol. Soc., 79, 197–217.

Rothrock, D.A., Y. Yu, and G.A. Maykut (1999): Thinning of the Arctic sea-ice

cover. Geophys. Res. Lett., 26, 3469–3472.

SEARCH SSC (2001): SEARCH: Study of Environmental Arctic Change, Science

Plan, 2001, Polar Science Center, Applied Physics Laboratory, University of

Washington, Seattle, 91 pp.
68 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

Shy, T.L., and J.E. Walsh (1999): Statistical analysis of atmospheric forcing of

North Pole ice draft variations. J. Geophys. Res., 104, 18,431–18,445.

Stern, H.L., D.A. Rothrock, and R. Kwok (1995): Open water production in Arctic

sea ice: Satellite measurements and model parameterizations. J. Geophys. Res.,

100, 20,601–20,612.

Thorndike, A.D., and R. Colony (1982): Sea ice motion in response to geostrophic

winds. J. Geophys. Res., 87, 5845–5852.

Tucker, W.B. III, J.W. Weatherly, D.T. Eppler, D. Farmer, and D.L Bentley (2001):

Evidence for the rapid thinning of sea ice in the western Arctic Ocean at the

end of the 1980s. Geophys. Res. Lett., 28, 2851–2854.

Vinje, T., N. Nordlund, and A. Kvambekk (1998): Monitoring ice thickness in Fram

Strait. J. Geophys. Res., 103, 10,437–10,449.

Wadhams, P. (1983): Sea ice thickness in the Fram Strait. Nature, 305, 108–111.

Wadhams, P., W.B. Tucker III, W.B. Krabill, R.N. Swift, J.C. Comiso, and N.R.

Davis (1992): Relationship between sea ice freeboard and draft in the Arctic

Basin, and implications for ice thickness monitoring. J. Geophys. Res., 97,

20,325–20,334.

Wadhams, P., and N.R. Davis (2000): Further evidence of ice thinning in the Arctic

Ocean. Geophys. Res. Lett., 27, 3973–3975.

Walsh, J.E., and others (2001): Enhancing NASA’s contribution to Polar Science.

National Academy of Sciences, National Academy Press, Washington, D.C.,

124 pp.

Zhang, J., and D.A. Rothrock (2001): A thickness and enthalpy distribution sea-ice

model. J. Phys. Oceanogr., 31, 2986–3001.
SEARCH Large-Scale Observations Workshop 69

6. An Arctic System Reanalysis

Compiled by John Walsh with contributions from Greg Flato, Jennifer Francis, Roy Jenne, Fedor Mesinger, Mark Serreze, and Pedro Viterbo.

6.1 Summary and Recommendations

A reanalysis may be regarded as a reconstruction of historical states of climate system components (e.g., the atmosphere, the ocean) or of the more

complete climate system. The general strategy is to use a model, based on

the physical and dynamical laws governing the system component(s), and

simulate variations over time while constraining the simulation to fit the

available observational data. A reanalysis can incorporate all observational

data deemed appropriate for an accurate reconstruction of the historical

state. It dynamically interpolates these observations in space and time while

imposing consistency with the physical and dynamical laws governing the

medium. In the case of the atmosphere or ocean, the output includes sets

of time-varying three-dimensional fields of variables such as temperature,

pressure, wind (or ocean currents). In addition, the output of a reanalysis can include model-estimated values of quantities that are generally not

widely available from observations, e.g., radiative fluxes, evaporation and

precipitation, ocean salinity, sea ice thickness, etc.

A key objective of the SEARCH workshop of 27–29 November was an assessment of the desirability and viability of an Arctic reanalysis. The workshop presentations and discussion provided various reasons why a compelling

case can be made for an Arctic regional reanalysis. First, the reanalysis

would produce long time series of temporally consistent fields (subject to

changes in observing system input) of Arctic upper-air and surface winds,

humidities, and temperatures for studies of circulation variability (e.g., the

AO, NAO, and their Arctic manifestations); for budget studies; and for the

driving of sea ice and ocean models. Second, the reanalysis would provide

a context for evaluations of ongoing and future changes in the Arctic, enabling a key objective of SEARCH to be addressed. Third, the reanalysis

would provide fields for which direct observations are sparse or problematic

(e.g., precipitation, evapotranspiration, radiation, and clouds). The fields

would be at relatively high resolution (e.g., 32 km in NARR), which is especially valuable in topographically and coastally complex areas. Fourth,

the system-oriented approach required for a reanalysis would provide a community focus, involving at least the Arctic terrestrial, sea ice, and atmospheric communities. Fifth, the reanalysis would leverage upon, and provide

a synthesis of, Arctic field programs (SHEBA, LAII/ATLAS, ARM,...), capitalizing upon prior investments by bringing field results to bear upon the

parameterizations used in large-scale models. Finally, the groundwork for

an Arctic regional reanalysis is now being laid by the improvements inherent

in ERA-40 and by NCEP’s North American Regional Reanalysis (NARR).

The coincidence of this groundwork and the spin-up of SEARCH provides

a unique window of opportunity for an Arctic reanalysis. Accordingly, the
70 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

panel recommends that SEARCH give priority to a reanalysis of the Arctic

system.

While the argument for an Arctic reanalysis is compelling, some cautions

emerged from the workshop. (1) A reanalysis of the Arctic atmosphere

and ocean should be run separately, making use of observed surface conditions, SST, snow cover, winds, etc. The inclusion of a fully coupled atmosphere/ocean appears to be premature in view of the current status of Arctic

Ocean models and data streams, so the inclusion of oceanic information in

a system reanalysis will require a carefully conceived strategy. (2) A major

challenge lies in the effective utilization of TOVS and other satellite data for

the Arctic, especially since a major reprocessing of the TOVS radiances will

be required. Even the conventional data to be assimilated will require significant effort in extraction and quality control. In addition, major technical

issues such as the choice of 4D-Var or 3D-Var data assimilation procedures

need to be addressed. (3) As implied by (2), the required commitment of

resources, both human and financial, is substantial if an Arctic reanalysis

is to be successful. The commitment appears to be most easily achievable if

an Arctic regional reanalysis is a follow-on to the North American regional

reanalysis at NCEP. Since the latter has only about 2 years until planned

completion, this strategy requires immediate involvement, by a core of Arctic

investigators, in planning activities with NCEP. In addition to the entrainment of potential sponsors, there must also be coordination with the TOVS

reprocessing, with diagnostic evaluations of the Arctic output from ERA-40

and the NARR, and with the preparation of input data streams. While the

window of opportunity is short and the required commitment is substantial,

an Arctic regional reanalysis has the potential to be a flagship activity in

SEARCH. It would provide SEARCH with an effective synthesis of efforts

in Arctic data analysis, polar remote sensing, Arctic field programs, and

large-scale modeling.

Recommended activities for the short term include the establishment of

an active liaison with the North American Regional Reanalysis project at

NCEP, the evaluation of the Arctic and subarctic output from the North

American reanalysis, the establishment of a process by which the needs of

the arctic community (and SEARCH in particular) are incorporated into the

NCEP regional reanalysis system, the extraction and preparation of Arctic

data that have not been used in reanalyses to date, and the preparation

of a version of the TOVS data suitable for inclusion in an Arctic regional

reanalysis. Longer-term activities include the recasting of component models

of sea ice, the ocean, and the arctic terrestrial system into forms suitable for

3-D or 4-D variational assimilation, the meshing of these models with the

established atmospheric reanalysis system, and the preparation of the data

streams to be ingested into the non-atmospheric components of an Arctic

system reanalysis.

6.2 Presentation and Discussion Issues

A prominent topic of discussion at the SEARCH Workshop was the possibility of an Arctic reanalysis. The panel discussion and presentations on
SEARCH Large-Scale Observations Workshop 71

NCEP ETA 32 km/45-layer Model Topography

Figure 6.1: North American Regional Reanalysis (NARR) domain and topography.

reanalysis included input from representatives of the major centers involved

in ongoing reanalysis efforts (Pedro Viterbo of ECMWF, Fedor Mesinger of

NCEP, Roy Jenne of NCAR) as well as from Arctic scientists (Mark Serreze, David Bromwich, Greg Flato, Jennifer Francis) who have been active

in the evaluation of model output, observational datasets, and remote sensing products of direct relevance to a possible Arctic regional reanalysis. The

consensus of the participants was that an Arctic reanalysis is an increasingly

attractive and viable possibility because of the conjunction of (a) ongoing reanalysis efforts at ECMWF and NCEP, (b) the recent involvement of Arctic

scientists in broader reanalysis efforts, (c) the recent production and evaluation of remote sensing products for the Arctic, e.g., TOVS, and (d) the

imminence of SEARCH, which can provide a scientific and organizational

framework in which an Arctic reanalysis would be a core activity. We summarize here the Arctic regional reanalysis issues addressed in the individual

presentations and in the general discussion sessions at the workshop. Since

the Arctic was considered by the group to extend to the southern boundaries of the northward-flowing rivers, it is implicit in this discussion that the

domain of an Arctic reanalysis must include some areas not traditionally

regarded as the Arctic.

The NCEP/NCAR global reanalysis has been completed for the period

back to 1948, and is being continued through the present. The major new

reanalysis activity at NCEP for the next 2 years is the North American Re-
72 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

gional Reanalysis. Preliminary results from NARR test years (1987, 1998),

shown by Fedor Mesinger, indicate that the regional reanalysis produces a

striking improvement in precipitation relative to the global reanalysis, and

that temperatures and winds from the surface to 200 mb are also improved

relative to the global reanalysis. With regard to particular model formulations, Mesinger pointed out that the land-surface model upgrades made

to the Eta model in July 2001 (and included in the current NARR system)

contain several important cold-season processes: patchy snow cover, frozen

soil (new state variable), variable snowpack density (new state variable), soil

heat flux below a snowpack, and a maximum snow albedo dependent on major vegetation ecosystems. The planned period of coverage of this reanalysis

is 1982–2003, and the domain includes much of the Arctic (Fig. 6.1). In this

respect the NARR offers a promising testbed for a possible follow-on regional

reanalysis for the Arctic. For example, both regional reanalyses would need

to be driven by a global reanalysis. During the 2-year production period for

the North American reanalysis, active diagnostic involvement by the Arctic

community could pave the way for a logical and timely transition to an Arctic focus. As yet, the Arctic community’s input concerning Arctic-specific

reanalysis issues has been less extensive with NCEP than with ECMWF.

Pedro Viterbo reviewed reanalysis efforts at ECMWF. While ECMWF

has no immediate plans for a regional reanalysis, it is in the midst of a

40+-year (1958–2001) global reanalysis known as ERA-40. This effort has

benefitted from (and will benefit in return) the Arctic research community,

largely through interaction with the ACSYS working group on reanalysis.

In the 6 years since the previous ECMWF reanalysis, ERA-15, two-thirds

of the modifications to surface and boundary-layer formulations at ECMWF

were motivated by high-latitude meteorology. The improvements are related

to processes such as soil freezing, infiltration of frozen soils, surface snow

cover, forest albedo in the presence of snow, and sea ice parameterizations.

These modifications have led to marked improvements in the simulations of

weather and climate in high latitudes. For example, surface air temperatures over southern Canada and eastern Asia have improved by 5–15◦C, and

the spring runoff peak in high latitudes is captured much more realistically

by ERA-40 than by ERA-15. Such improvements represent the fruits of

significant collaboration between a major modeling center and the Arctic

community. The ECMWF-Arctic experience to date points to several necessary ingredients for a polar regional reanalysis: (1) inclusion of model physics

that realistically represents phenomena specific to high latitudes (snow cover

is an especially important consideration), (2) accurate specifications of lake

temperatures, which can contribute significantly to the surface energy budget and the seasonality of near-surface air temperatures. As an example of

(1), Fig. 6.2 illustrates the effect of a more realistic formulation of albedo

in areas where vegetation has a significant masking effect on snow. Other

“lessons” to be noted from the ECMWF experience in reanalysis are that an

extensive testing phase (∼25 years of data assimilation in the case of ERA40) is necessary prior to the production run, and that a critical mass of

personnel are required (five dedicated scientists, plus support from other departments at ECMWF, for ERA-40). The testing phase requires evaluations
SEARCH Large-Scale Observations Workshop 73

124

110

90

70

50

30

10

–10

–30

–50

Figure 6.2: Difference in net shortwave radiation at the surface between the ERA40 system and the ERA15

system, averaged for April 1992. The figure shows a large increase in snow covered areas.

of various measures of accuracy of the reanalysis, not only on a large-scale

(e.g., Arctic-wide) basis but also for specific regions within the Arctic. For

example, the ACSYS working group on reanalysis has already uncovered a

problem with the assimilation of TOVS data into ERA-40 over the central

Arctic. This problem is apparent in the geopotential height fields, and it

highlights the continuing need for proper handling of TOVS data over the

data-sparse central Arctic.

Data inputs for any Arctic reanalysis will require a substantial effort prior

to the actual assimilation activity. Roy Jenne of NCAR pointed out that key

needs are (1) the addition to the database for reanalysis input of previously

unused (or under-used) conventional data, including Canadian rawinsonde

reports prior to July 1955, additional Canadian pressure and temperature

reports from the 1948–1966 period, and the routine upper-air measurements

from drifting ice stations (e.g., T-3 and the Russian NP series); (2) optimum

uses of the VTPR and TOVS information, which together provide satellite

inputs back to 1972. It is noteworthy that, in some respects, there is potentially better observational coverage for the upper-air in the earlier (pre-1980)

decades when there were more permanent ocean weather ships (and ice sta-
74 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

tions), more rawinsonde sites, more frequent reconnaissance flights over the

Arctic, and more dropsondes over the Arctic Ocean. In order to realize the

full benefits of this information, however, it will be necessary to perform considerable data archeology in the Former Soviet Union to uncover and extract

the wide variety of atmospheric, land surface, and probably oceanic data

that most likely exist. Jenne also stressed the advantages of the so-called

“4D-Var” data assimilation scheme, which fits the analysis to observations

over an entire 6–12 hour window, relative to the more traditional “3D-Var”

procedure and its “snapshot” approach to fitting the observations.

Among the “lessons learned” from the NCAR experience in providing

data for assimilation into the NCEP and ECMWF reanalyses are that the

data collection, error-checking, and quality-control tasks are substantial.

Consequently, the Arctic community would be well-advised to initiate soon

any data synthesis efforts that will be needed for an Arctic regional reanalysis. Roy Jenne and Roger Colony also noted that many Arctic datasets

extend back well beyond the 50-year time frame of present reanalyses, offering the possibility of more limited data analyses (i.e., not a full-blown

reanalysis) for longer periods in order to provide more specific benchmarks

for change detection. (Much of the atmospheric data extending back to the

1800s resides in the NCDC library in Asheville.)

While the NP and other observations from the central Arctic represent

potentially valuable inputs and can provide opportunities for calibration and

validation, they do not provide the space-time coverage needed over the Arctic Ocean and the surrounding seas. Remotely sensed data, particularly from

TOVS, must assume a particularly important role in an Arctic regional reanalysis. However, as noted by Jennifer Francis, the present status of the calibration of radiances falls short of the requirements for climate applications.

Several recommendations concerning TOVS were made at the workshop: (1)

NOAA/NESDIS, as caretaker of the TOVS data, should assume the task of

correcting biases in global radiance data in order to optimize their usage

in reanalyses; (2) a focus on radiance bias corrections for polar conditions

needs to be provided by a designated group composed of representatives from

the polar user community, reanalysis centers, retrieval algorithm developers,

and NESDIS; (3) residual uncertainties should be quantified to aid in trend

assessments and other uses of the products. With regard to (1) and (2), an

effort is now underway to assemble a team, to include university and NOAA

scientists as well as reanalysis experts, in order to make the bias corrections

for the Arctic. The reprocessing will be directed at the assimilation of the

radiances into reanalyses. For reanalysis purposes, there is a need to extend

the retrieval-based dataset using the bias-corrected radiances; specific tasks

with regard to Path-P include modification of the algorithms for use over

high terrain, improvement of cloudy retrievals, extension temporally to the

present, and extension spatially to 45◦N or to a latitude that dovetails with

the corresponding global dataset of retrievals. The retrieval of upper-level

winds also requires attention in the context of reanalysis. Validation against

rawinsonde reports offers one means for assessing the assimilated radiances

and winds.

As indicated by the summary above, much of the discussion focused on
SEARCH Large-Scale Observations Workshop 75

atmospheric models and the utilization of atmospheric data. A key issue in

Arctic reanalysis is the interdisciplinary scope of the activity. Greg Flato

noted that global atmospheric reanalyses show increasing (albeit coarseresolution) success in the Arctic, although cloud/radiative interaction and

the simulation of surface pressure (wind) patterns appear to merit increased

attention. The viability of including other climate system components (ocean,

sea ice, terrestrial) is a function of the readiness of the models and, perhaps

more importantly, the availability of data for assimilation and validation.

Flato suggested that sea ice is a good candidate for inclusion, since a variety of ice models are well established and the observational databases of ice

coverage (concentration) and ice motion are substantial. A sea ice model

contains sufficient “physical” information that it should indeed be beneficial to a reanalysis effort, since the model information would offset to some

degree the (poorly characterized) errors in the ice observations. The potential to obtain ice thickness as a derived product makes a sea ice model

an especially attractive candidate for inclusion in an Arctic reanalysis. The

ice thickness information, in turn, can improve the estimates of the surface

fluxes over sea ice. However, Arctic ocean models and ocean data streams

do not appear to have reached this stage of readiness, making it difficult

to establish credibility through validation. One may also argue that it will

even take a significant research effort to recast a typical ocean–sea ice model

into a form suitable for 3-D or 4-D variational assimilation, and even more

effort to merge the recast model with an established atmospheric reanalysis

system.

Recent results from terrestrial packages, such as the TESSEL module

used by ECMWF, indicate that the inclusion of the terrestrial component

may be viable, although underlying issues of validation and feedbacks to

the atmosphere need more thorough consideration. Land surface data assimilation is already performed through the inclusion of snow information

from surface stations, some (but not all) of which are included in ERA-40.

The ERA-40 results highlight the importance of the accurate representation of snow cover extent. There remains the challenge of incorporating

remotely sensed information on the terrestrial component, particularly snow

water equivalent and vegetative characteristics. The seasonal and spatial

variations of the latter represent a prime opportunity for entrainment of the

terrestrial community into the reanalysis effort.

Finally, Flato addressed the underlying “hypothesis” that the highestquality reanalysis results, in principle, from a system ingesting all available

data (subject to caveats that the error variances must be known, etc.). This

hypothesis requires a degree of “faith” on the part of the user of the assimilated data, whereas demonstrable quality (and quantitative measures

of that quality) derive from comparisons to independent data with suitable

sampling and other characteristics. Data from field campaigns provide one

source of such comparison data, but the sampling issues can introduce difficulties into the evaluation. One can argue that a more systematic, ongoing

“quality assurance” system would be beneficial, even during the production

phase of a reananlysis. While this type of activity has, to varying degrees,
76 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

been part of past reanalyses, it may be especially important in a reanalysis

for a relatively data-sparse region such as the Arctic.

7. International Coordination

SEARCH involves large-scale covariability of Arctic change and thus there

is clear need for improved planning for international coordination. Howard

Cattle from the Met Office, Bracknell, UK, provided a review of the WCRP

Arctic Climate System Study (ACSYS) and Cryosphere and Climate Project

(CliC). Barry Goodison reviewed the current situation in Canada. European

planning for Arctic monitoring is underway (Johannessen et al., 1997).

The ACSYS was a 10-year program with a sunset date at the end of

2003. Progress with ACSYS includes:  Increased range and accessibility of sea ice data sets on CD-ROM  Establishment of the in situ ice thickness database  Work to assess and improve polar aspects of atmospheric reanalysis  Continue development of Arctic runoff and precipitation archives  Ice-ocean interaction modeling studies and hydrological model intercomparisons  Development of the Arctic data and information service

The goals of CliC are  Improve understanding of the physical processes and feedbacks between the cryosphere and climate system  Improve cryosphere representation in climate models  Assess impacts of past and future climate variability of the cryosphere  Enhance observation and monitoring

Potential areas of joint SEARCH-ACSYS/CliC collaboration are  Establishing and maintaining long-term observations in the Arctic to

detect and track environmental climate change  Collaborating in the promotion of modeling efforts to synthesize observations, the representation of climate processes in models, and the

simulation and prediction of Arctic change  Promoting appropriate process studies to understand potentially important feedbacks  Promoting the application of knowledge of Arctic climate change to

provision of scenarios for appropriate impact studies
SEARCH Large-Scale Observations Workshop 77

 Exchange of up-to-date information with regard to data management

systems being used within SEARCH and ACSYS/CliC and coordinate

if possible  Cross SSG/SSC representation to build links  Joint sponsorship of meetings, workshops, and conferences where appropriate

It should also be noted that there is a joint SEARCH-CLIVAR (Climate Variability) working group to coordinate research on physical climate

change in the Arctic and Arctic/lower latitude interactions. Coordination

with Russia is an important issue; there are promising developing activities

in hydrology.

7.1 Reference

Johannessen, O.M., E. Bjørgo, and M. Miles (1997): Operational Climate Monitoring Program for Arctic Ice Cover. In: Operational Oceanography: The Challenge

for European Cooperation, J.H. Steel et al. (eds.), Elsevier, 361–367.

8. Acknowledgments

We appreciate the support for the Workshop from NASA, Department of Energy,

Office of Naval Research, National Science Foundation, the SEARCH Project Office,

and NOAA, through the SEARCH Interagency Working Group (IWG). We wish

to thank all the participants, who provided ideas, time, and information to this

effort. Beverly Pelto did an outstanding job with the Workshop logistics, and Joyce

Gearhart and Ryan Layne Whitney helped produce the Workshop Report. Karen

Ventenbergs designed the cover.
78 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh
SEARCH Large-Scale Observations Workshop 79

Appendix A: Agenda

SEARCH Workshop on Large-Scale

Atmosphere/Cryosphere Observation

27 November 2001—Background Talks

“Setting the Stage”

8:15 a.m. James Morison Introduction to SEARCH

8:30 a.m. Jim Overland Introduction to Workshop

8:45 a.m. Lawrence Mysak The Changing Arctic

9:15 a.m. Mike Wallace Annular Modes

9:45–10:15 a.m. Break

10:15 a.m. Steven Pawson Stratospheric Change

10:45 a.m. David McGuire Monitoring the Biosphere

11:15 a.m. Don Perovich Sea Ice—Spanning the Scales

11:45 a.m. Roger Colony Retrospective—Temperature and Sea Ice

12:15–1:20 p.m. Lunch

“Observations—Preview”

1:30 p.m. Drew Rothrock In Situ and Derived Sea Ice Thickness Observations

2:00 p.m. Barry Goodison Surface Observation Network

2:30 p.m. Larry Hinzman Hydrology and CHAMP

3:00 p.m. Taneil Uttal Intensive Sites

3:30–3:45 p.m. Break

“Data Assimilation and Modeling”

3:45 p.m. David Bromwich Plan for an Arctic Reanalysis

4:15 p.m. Pedro Viterbo Experience at ECMWF

4:45 p.m. John Walsh Fully Coupled Models

5:30 p.m. Reception
80 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

28 November 2001

8:30–8:45 Introduction to Panels—Jim Overland

8:45–11:45 a.m. Sea Ice Observations—Discussion

Panel: Don Cavalieri

Greg Holloway

Ron Lindsay

Ola Persson

Ignatious Rigor

Jackie Richter-Menge, Chair

11:45–1:00 p.m. Lunch

1:15–4:15 p.m. Atmospheric Observations—Discussion

Panel: Roy Jenne

Jeff Key

Steven Pawson

Bob Stone

Mike Wallace

Jennifer Francis

Jim Overland, Chair

4:15–4:45 p.m. International Connections—Howard Cattle

29 November 2001

8:30–11:30 a.m. Land Observations—Discussion

Panel: Claude Duguay

Barry Goodison

Ed Josberger

David McGuire

Vladimir Romanovsky

Bernie Zak

Roger Barry, Chair

11:30–12:50 p.m. Lunch

1:00–4:00 p.m. Arctic Reanalysis—Discussion

Panel: Greg Flato

Bob Grumbine

Roy Jenne

Amanda Lynch

Mark Serreze

John Walsh, Chair

4:00–5:00 p.m. Summary Reports

Sea Ice Richter-Menge

Atmosphere Overland

Land Barry

Reanalysis Walsh
SEARCH Large-Scale Observations Workshop 81

Appendix B: Participants

Name Phone Number E-mail Address

Abdalati, Waleed 202-358-0746 wabdalatihq.nasa.gov

Anderson, Don 202-358-1432 x2770 danders1hq.nasa.gov

Barry, Roger 303-492-5488 rbarrykryos.colorado.edu

Becker, Peter 360-417-9293 p becker 1998yahoo.com

Bitz, Cecilia 206-543-1339 bitzapl.washington.edu

Brigham, Lawson 703-525-0111 l.brighamarctic.gov

Bromwich, David 614-292-6692 bromwichpolarmet1.mps.ohiostate. edu

Calder, John 301-713-2518 x288 John.Calder@noaa.gov

Cattle, Howard hcattle@meto.gov.uk

Cavalieri, Don 301-286-2444 don.cavalieri@gsfc.nasa.gov

Colony, Roger 907-474-5115 rcolony@iarc.uaf.edu

Dick, Chad 47 77 75 0145 (Norway) chad@npolar.no

Dirks, Dick 303-497-8987 dirks2@ucar.edu

Divoky, George 206-365-6009 fngjd@uaf.edu

Duguay, Claude 418-656-2131 x3461 claude.duguay@ggr.ulaval.ca

Dumas, Jackie 250-472-4003 jdumas@ocean.seos.uvic.ca

Fetterer, Florence 303-492-4421 Florence.Fetterer@noaa.gov

Flato, Greg 250-363-8233 greg.flato@ec.gc.ca

Francis, Jennifer 732-708-1217 francis@imcs.rutgers.edu

Goodison, Barry 416-739-4345 Barry.Goodison@ec.gc.ca

Grenfell, Tom 206-543-9411 tcg@atmos.washington.edu

Grumbine, Bob 301-763-8133 wd21rg@sun1.wwb.noaa.gov

Hickey, Hannah hickeyh@ocean.seos.uvic.ca

Hinzman, Larry 907-474-7331 ffldh@uaf.edu

Holloway, Greg 250-363-6564 hollowayg@pac.dfo-mpo.gc.ca

Jenne, Roy 303-497-1215 jenne@ncar.ucar.edu

Josberger, Ed 253-428-3600 x2643 ejosberg@usgs.gov

Key, Jeff 608-263-2605 jkey@ssec.wisc.edu

Kwok, Ron 818-354-5614 ron@rgps1.jpl.nasa.gov

Lettenmeier, Dennis 206-543-2532 dennis1@u.washington.edu

Light, Bonnie 206-543-0628 bonnie@atmos.washington.edu

Lindsay, Ron 206-543-5409 lindsay@apl.washington.edu

Lynch, Amanda 303-492-5847 manda@tok.colorado.edu

Martin, Seelye 206-543-6438 seelye@ocean.washington.edu

McGuire, David 907-474-6242 ffadm@aurora.uaf.edu

McNutt, Lyn 907-474-6077 lyn@dino.gi.alaska.edu

Mesinger, Fedor 301-763-8000 x7249 Fedor.Mesinger@noaa.gov

Moore, Jim 303-497-8635 jmoore@ucar.edu

Morison, James 206-543-1394 morison@apl.washington.edu

Moritz, Dick 206-543-8023 dickm@apl.washington.edu

Muench, Robin 703-588-2902 rmuench@nsf.gov

Mysak, Lawrence 514-398-3768 mysak@zephyr.meteo.mcgill.ca
82 Principal Authors: Overland, Fetterer, McGuire, Richter-Menge, Walsh

Name Phone Number E-mail Address

O’Connor, Chris 301-457-5303 x304 coconnors@natice.noaa.gov

Overland, Jim 206-526-6795 overland@pmel.noaa.gov

Pawson, Steven 301-614-6159 spawson@dao.gsfc.nasa.gov

Pelto, Beverly 206-685-8290 pelto@apl.washington.edu

Perovich, Don 603-646-4255 perovich@crrel.usace.army.mil

Persson, Ola 303-497-5078 opersson@etl.noaa.gov

Prius, Matthew 425-644-9660 x311 matt@nwra.com

Proshutinsky, Andrey 508-289-2796 aproshutinsky@whoi.edu

Putkonen, Jaakko 206-543-0689 putkonen@u.washington.edu

Richter-Menge, Jackie 603-646-4266 Jacqueline.A.Richter-Menge@erdc.usace.army.mil

Rigor, Ignatious 206-685-2571 igr@apl.washington.edu

Romanovsky, Vladimir 907-474-7459 ffver@uaf.edu

Rothrock, Drew 206-685-2262 rothrock@apl.washington.edu

Savelieva, Nina 907-474-1951 nsavelieva@iarc.uaf.edu

arctic@online.marine.ru (after 12/15)

Schweiger, Axel 206-543-1213 axel@apl.washington.edu

Serreze, Mark 303-492-2963 serreze@kryos.colorado.edu

Sheridan, Pat 303-497-6672 Patrick.Sheridan@noaa.gov

Smemiletov, Igor 907-474-6286 igorsm@iarc.uaf.edu

Soreide, Nancy 206-526-6728 nns@pmel.noaa.gov

Steffen, Koni 303-492-4524 koni@seaice.colorado.edu

Stone, Bob 303-497-6056 Robert.Stone@noaa.gov

Tucker, Terry auwbt@uaa.alaska.edu

Uttal, Taneil 303-497-6409 taneil.uttal@noaa.gov

Viterbo, Pedro pav@ecmwf.int

Wadhams, Peter 44-223-336542 (UK) pw11@cam.ac.uk

Wallace, Mike 206-543-7390 wallace@atmos.washington.edu

Walsh, John 217-333-7521 walsh@atmos.uiuc.edu

Wang, J.A. 907-474-2685 jwang@iarc.uaf.edu

Wang, Muyin 206-526-4532 muyin@pmel.noaa.gov

Weaver, Ron 303-492-7624 weaverr@kryos.colorado.edu

Wood, Kevin 206-550-6934 kwood@u.washington.edu

Zak, Bernie 505-845-8631 bdzak@sandia.gov