SCICEX Phase II

Science Plan

Part 1: Technical Guidance for Planning

Science Accommodation Missions
The SCICEX Science Plan, Part I, was prepared by the 

SCICEX Science Advisory Committee:

Jackie Richter-Menge, Chair�������ERDC-Cold Regions Research and Engineering 

Laboratory, USACE, Hanover, NH

Tim Boyd ����������������������������The Scottish Association for Marine Science, Oban, 

Scotland, UK

Margo Edwards���������������Hawaii Institute of Geophysics and Planetology, 

University of Hawaii, Honolulu, HI

Ray Sambrotto�����������������Lamont-Doherty Earth Observatory of Columbia University, 

Palisades, NY

Bill Smethie������������������������Lamont-Doherty Earth Observatory of Columbia University, 

Palisades, NY

Terry Tucker����������������������Retired, ERDC-Cold Regions Research and Engineering 

Laboratory, USACE, Hanover, NH

Mark Wensnahan�����������Polar Science Center, Applied Physics Laboratory, 

University of Washington, Seattle, WA

Jeff Gossett������������������������Arctic Submarine Laboratory, US Navy, San Diego, CA

Martin Jeffries������������������Office of Polar Programs, National Science Foundation, 

Arlington, VA

CAPT Doug Marble������Office of Naval Research, Arlington, VA

This report should be referenced as:

SCICEX Science Advisory Committee. 2010. SCICEX Phase II 

Science Plan, Part I: Technical Guidance for Planning Science 

Accommodation Missions. US Arctic Research Commission, 

Arlington, VA, 76 pp.
SCICEX Phase II

Science Plan

Part 1: Technical Guidance for Planning

Science Accommodation Missions

Contents

Abstract...........................................................................................................................................................................................1

Introduction.............................................................................................................................................................................2

Framework....................................................................................................................................................................................5

Approach.........................................................................................................................................................................................7

SAMs Sampling Priorities and Recommendations............................................................................. 11

Overarching...................................................................................................................................................................................... 11

Ice Draft Profiling........................................................................................................................................................................... 11

Ocean: Hydrography.................................................................................................................................................................... 14

Ocean: Chemistry.......................................................................................................................................................................... 18

Ocean: Biology................................................................................................................................................................................ 23

Bathymetry........................................................................................................................................................................................ 26

Summary........................................................................................................................................................................................ 29

References.................................................................................................................................................................................... 31

Appendix A: Planning Matrix............................................................................................................................................... 35

Appendix B: Original SCICEX Memorandum of Agreement.............................................................................. 54

Appendix C: Current (Phase II) SCICEX Memorandum of Agreement........................................................ 62

Appendix D: Acronyms........................................................................................................................................................... 75

1

The SCience ICe EXercise (SCICEX) program, formally established in 1994, recognizes the unique capabilities of nuclear-powered submarines as data-collection 

platforms in the ice-covered Arctic Ocean. In reaction to a decision to end an 

initial sequence of cruises solely dedicated to science, the SCICEX program 

was modified in 2000 to include Science Accommodation Missions (SAMs). 

In the course of a SAM, some time is set aside for the collection of unclassified 

data during otherwise classified submarine exercises. Due to security issues, the 

SAM process does not allow for significant advance planning of scientific activities. Instead, the Navy’s Arctic Submarine Laboratory (ASL) will work with the 

operational Navy to identify and plan SCICEX SAM opportunities. Input to 

ASL from the scientific community regarding data collection is provided via this 

science plan. The centerpiece of the SCICEX Science Plan, Part 1, is a detailed, 

prioritized list of sampling recommendations for sea ice draft profiling; ocean 

hydrography, chemistry, and biology; and bathymetry. The recommendations are 

based on the current state of knowledge as derived from observations and models. 

Management and community access to these data will be the focus of part 2 of the 

science plan. The SCICEX Science Advisory Committee (SAC) is responsible for 

periodic review and, if appropriate, updating the science plan to keep pace with 

the advancement of state-of-the-art knowledge and technology. The SCICEX SAC 

will also assist the Navy in evaluating the efficacy of SAMs to generate suggestions 

aimed at improving future missions.

Abstract
2

In 1993, the United States Navy and the Arctic marine 

research community undertook a scientific research 

cruise aboard a nuclear-powered submarine in an 

ambitious program to evaluate the use of nuclearpowered submarines for scientific studies of the 

Arctic Ocean (Figure 1). This collaboration recognized the unique capabilities of these submarines as 

data-collection platforms in the Arctic Ocean, coupling 

the ability to travel at high speed with the ability to 

operate across the region regardless of the state of the 

sea ice cover. It was anticipated that these capabilities 

could be applied to collecting data that describe the ice 

canopy; physical, chemical, and biological water properties; and the seafloor and underlying sediments and 

bedrock. In contrast to standard operating procedures 

for naval nuclear submarines, data collected within 

a designated area (Figure 1) during the cruise were 

disseminated to participating 

scientists shortly after completion of the survey.

The success of this initial 

collaboration and the associated pilot cruise served 

to launch the SCience ICe 

EXercise (SCICEX) program. The initial SCICEX 

Memorandum of Agreement 

(MOA; Appendix B) was signed 

in 1994 by elements of the 

U.S. Navy, the National Science 

Foundation (NSF), the National 

Oceanic and Atmospheric 

Administration (NOAA), and 

the U.S. Geological Survey 

(USGS). The MOA stated:

The overall goal of SCICEX is to improve understanding 

of Arctic Ocean processes and their role in the Earth’s 

climate system by dual use of nuclear submarines, thus 

fully capitalizing on existing national platform capabilities. This Agreement is intended to mutually support the 

objectives of both the civilian and military communities.

The original MOA supported five more dedicated 

science cruises aboard nuclear-powered submarines between 1995 and 1999. In October 1998, the 

U.S. Navy determined that it would no longer be 

able to support dedicated science cruises. Rather 

than terminate the SCICEX program, a second 

MOA was negotiated and signed in 2000 between 

elements of the U.S. Navy and NSF (Appendix C). 

Maintaining the same core goals and objectives, the 

SCICEX Phase II MOA modified the scope of the 

Introduction

Figure 1. Arctic Ocean bathymetry with identified geographic features referred to in the 

text: Gakkel Ridge (GR), Amundsen Basin (AB), Lomonosov Ridge (LR), Makarov Basin (MB), 

Mendeleyev Ridge (MR), Alpha Ridge (AR), Chukchi Plateau (CP), and Canada Basin (CB). The 

SCICEX Data Release Area is outlined in yellow.
3

collaboration to include Science 

Accommodation Missions 

(SAMs). During a SAM, some 

time is set aside for the collection of unclassified data during 

otherwise classified submarine 

exercises. SCICEX accommodation cruises have taken 

place in 2000, 2001, 2003, and 

2005. The Phase II MOA is, and 

will remain, in effect until it is 

deemed obsolete or impractical by the parties involved 

in its application. 

Comprehensive summaries 

of SCICEX cruises prior to 

2001 can be found in Rothrock 

et al. (1999a) and Edwards and 

Coakley (2003). Figure 2 shows SCICEX transits to 

date, including both dedicated and SAM deployments.

The Navy continues to send submarines to the Arctic. 

The expectation is that, for the foreseeable future, 

small amounts of time during selected cruises will be 

available for science data acquisition. The process by 

which the Navy expects to make unclassified Arctic 

submarine sampling time available to the scientific 

community through SCICEX SAMs does not allow 

for significant advance planning of scientific activities. 

As a result, detailed cruise-specific scientific civilian 

planning cannot be carried out prior to these missions. 

Instead, the science community has the opportunity, 

via this Science Plan, Part 1, to provide a detailed, prioritized list of data-collection efforts considered suitable for SCICEX accommodation cruises. This guidance, provided in a Planning Matrix (Appendix A), is 

intended to serve as a planning tool for SAMs, while 

at the same time understanding and appreciating that 

priority will be given to operational requirements 

during the cruise.

The Arctic research community developed the Science 

Plan, Part 1, to maximize SCICEX contributions 

toward understanding Arctic Ocean processes and 

their role in Earth’s climate system. Specifically, SAM 

cruises will collect baseline data on the ice canopy; 

physical, chemical, and biological water properties; and 

the seafloor. The science plan presents priority recommendations, structured within the framework of the 

SCICEX Phase II MOA, for scientific data collection 

during SAM cruises. Detailed SCICEX data-collection 

plans for a particular cruise will depend strongly on 

cruise mission requirements and the collection capabilities of the submarine involved. These constraints 

Figure 2. Summary of SCICEX cruise tracks to date.
4

necessitate a science plan that is inherently flexible, 

outlining a wide range of sampling options to maximize data-collection opportunities. 

Science Plan, Part 1, recommendations were developed 

with an eye toward making SCICEX an integral element of the Arctic Observing Network (AON; IARPC, 

2007), itself an integral component of the Study of 

Environmental Arctic Change (SEARCH) program. 

AON’s objectives are to enhance, coordinate, and 

sustain observing sites, systems, and networks in the 

Arctic. It is expected that data from this coordinated 

network will contribute information on the magnitude, 

variation, and rate of current and past environmental 

change. Further, these data will be used to initialize, 

validate, and improve computer models that allow 

simulation and prediction of the Arctic environmental system and its global connections. SCICEX data 

are well suited to contribute to AON. In particular, 

SCICEX looks to support repeated surveys of ice, 

ocean, and seabed properties in specific regions of the 

Arctic Basin (particularly those areas difficult to access 

by other means) that build on the historical records 

from SCICEX and other programs. 

The Science Plan, Part 1, includes sampling recommendations for ice draft profiling; ocean hydrography, 

chemistry, and biology; and bathymetry. The recommendations are explained in the context of past related 

SCICEX contributions and the current understanding 

of the Arctic Ocean environment, identified knowledge 

gaps, and submarine sampling capabilities. The current understanding is based on direct observations, 

process studies, and computer model simulations. The 

science plan is developed with the expectation that the 

recommended sampling strategies will be reviewed and 

updated by the SCICEX Science Advisory Committee 

(SAC) to keep pace with the advancement of stateof-the-art knowledge and technology and, hence, the 

evolution of new scientific questions and needs. 

Part 1 of the science plan responds to the urgent 

requirement to provide sampling guidance to the 

U.S. Navy Arctic Submarine Laboratory (ASL) to 

facilitate the continuation of the SCICEX program. 

Notably absent from this part of the plan is detailed 

guidance on another critical issue: community access 

to SCICEX data. This topic will be addressed in a 

separate, companion document that focuses on the 

management, quality control, and availability of data 

collected via a SCICEX SAM. Although the details 

remain to be worked out, it is the intention that data 

collected during the science elements of a SAM cruise 

will be publicly available as soon a possible after 

completion of the cruise. In contrast to the dedicated 

SCICEX missions, data from the SAMs will be disseminated in the public domain without first being held 

for exclusive use by any particular scientist or group 

of scientists. In accordance with the SCICEX Phase II 

MOA, all SCICEX SAM data will be accessible through 

the National Snow and Ice Data Center (NSIDC). 

The SCICEX SAC, in coordination with the SCICEX 

Interagency Committee, will inform the scientific 

community of the release of declassified SCICEX SAM 

data to the NSIDC through the best available medium 

(e.g., ArcticInfo information server operated by the 

Untied States Arctic Research Consortium). 
5

As outlined in the SCICEX Phase II 

MOA, the primary objective of 

Science Accommodation Missions is 

to collect baseline data rather than to 

conduct individual experiments. These 

baseline data are intended to permit 

continued monitoring of evolving sea 

ice and ocean conditions and, potentially, contaminant concentrations, as 

well as mapping of seafloor morphology in the Arctic Ocean. Navy personnel embarked on the ship, including 

ASL personnel, will be responsible for 

collecting the data and samples. It is 

not expected that civilian scientists 

will embark on SAM cruises.

Currently, there are two types of Arctic missions 

conducted by U.S. submarines that can be used as 

SAMs (Figure 3): 

a. Direct transits. Submarine transits occur across the 

Arctic Basin, from the Atlantic to the Pacific Ocean 

or from the Pacific to the Atlantic, typically one to 

three times per year.

b. Ice camps. Approximately every two years, the Navy 

will establish an ice camp in the southern Beaufort 

Sea to support its submarine Ice Exercise (ICEX) 

activities. Submarines operating at the ice camp will 

transit the Arctic Basin en route to the camp. These 

missions typically occur in March and April. 

Data collection during a SCICEX SAM is restricted to 

the Data Release Area, also referred to as the SCICEX 

box (Figure 1). The Navy has approved declassification 

and release of data in this region. Data release is further restricted to times when the submarine is operating at depths less than or equal to 244 m (800 ft) and 

speeds less than or equal to 25 kt. Designation of an 

Arctic submarine cruise as a SCICEX SAM by the Navy 

provides assurance to the scientific community that 

the Navy will make an effort to operate continuously 

within the parameters identified above, thus ensuring 

expeditious release of the data for scientific purposes. 

Baseline data collected during a SCICEX SAM will 

normally be limited to measurements that can be 

obtained using standard submarine equipment, systems that have been installed by ASL to support ICEX 

cruises, and other sensors that can be readily accommodated. Specific data sets and equipment will vary 

depending on the submarine class conducting the 

operations but will generally include: 

• Conductivity, temperature, depth (CTD) profiles 

taken by expendable probes

• CTD and other sensor data taken from hullmounted systems 

• Bathymetry recorded by installed fathometers

Framework

Figure 3. Cruise tracks for routine, direct crossings.
6

• Ice profile data from upward-looking sonar

• Water samples for salinity calibration and other 

later analyses

• Supporting navigation from the submarine’s inertial navigation system, and operational data at a 

nonclassified level

Although collection of baseline data, as described 

in this report, is the primary objective of a SCICEX 

SAM, independent proposals may be entertained. 

These proposals may include, but are not limited to, 

individual experiments or installation of auxiliary 

equipment. It needs to be understood that the proposed work must be consistent with maintaining the 

security of planned submarine operations. The decision to support proposed sampling will be made by the 

SCICEX Interagency Committee (IAC), with concurrence from an identified funding source. The SCICEX 

IAC includes representatives from NSF, the Office of 

Naval Research (ONR), and ASL. Investigators seeking funding for SCICEX-related observations and/

or research should contact either the ONR (Division 

Director, Ocean-Atmosphere-Space Research Division, 

Code 322, phone 703-696-4118) or NSF (Office of 

Polar Programs, Program Director, Arctic Observing 

Network, phone: 703-292-7442) to discuss the proposed work and for advice about submitting proposals. Investigators planning a proposal to ONR or NSF 

should also contact the Technical Director, ASL, to 

discuss the feasibility of their plans (http://www.csp.

navy.mil/asl/index.htm). Proposals must be submitted 

to each agency according to their established guidelines 

and procedures, and they will be subject to each agency’s normal review/approval/funding process. Neither 

ONR nor NSF guarantees that funding will be made 

available. Questions regarding the process of proposal 

submission can also be directed to the Chair, SCICEX 

Science Advisory Committee (contact information for 

current chair is available from the U.S. Arctic Research 

Commission Web site at http://www.arctic.gov). 

SCICEX IAC points of contact can also be found at 

http://www.scicex.org.
7

Approach

When submarines are scheduled for Arctic operations, ASL will examine each mission for its potential 

to collect SCICEX data. In doing so, they will consider 

the following:

• Type/destination of the transit

• Priorities laid out in the Science Plan, Part 1 

(this document)

• Suitability of the submarine’s equipment for 

data collection 

• Amount of time that might be added to the transit 

to perform data collection

• Time of year

• Complementary plans of other elements 

within AON

• Sampling conducted on recent previous SAM cruises

• Feasibility and cost-effectiveness of installing extra 

scientific equipment on board the submarine

The science plan is built around 

five recommended sampling 

corridors within the SCICEX 

Data Release Area (Figure 4). 

Specific cruise tracks, formed 

either within single corridors 

or as combinations of segments of one or more corridors, 

provide examples of what is 

anticipated to be executed, in 

actual practice, by the submarine (Figure 5, Table 1). These 

cruise tracks represent variations on the two most likely 

Navy scenarios under which 

SAM time will become available. As described earlier, these 

scenarios include (1) AtlanticPacific submarine transfers 

(i.e., transits from the Pacific to the Atlantic Ocean and 

vice versa), and (2) transits to and from a dedicated ice 

camp in the Beaufort Sea (Figure 3). The extent of the 

deviations of these cruise tracks from the pure transit 

tracks depends on the amount of additional science 

sampling time to be made available by the Navy. The 

additional sampling time is not anticipated to exceed 

three days for a single cruise. The sample cruise tracks 

are intended to provide a planning tool to the Navy, via 

ASL, for specific SAM opportunities. They also offer 

guidance to the scientific community with respect to 

sampling expectations.

Specific sampling recommendations are outlined in a 

Planning Matrix (Appendix A), as a function of candidate cruise tracks and various allotments of additional 

sampling time. These recommendations address specific 

scientific objectives as outlined in the next section. 

Individual recommendations address bathymetric, ice 

Figure 4. Recommended sampling corridors.
8

cover, and ocean water measurements. The ocean water 

measurements are further subdivided into hydrography, 

chemistry, and biology. Each set of recommendations 

assumes that the time available for SCICEX measurements during a particular deployment can be fully 

dedicated to that particular topical emphasis. For 

example, given a one-day window for sampling, the recommended ice cover measurements assume one day of 

sampling time independent of the other recommendations. This approach is consistent with the objective of 

providing maximum flexibility and, hence, maximizing 

the opportunities to collect SCICEX data. 

The dedicated science cruises of the 1990s balanced the 

sampling needs of the different marine science communities represented in the program. Similarly, the 

science plan presented here is an attempt to balance 

the sampling needs and priorities of these communities. By presenting a plan that targets sampling within 

discrete corridors (rather than specific track lines) 

we aim to introduce the flexibility to simultaneously 

meet the objectives of more than one constituency. 

For example, repeated sampling of the long, central 

cruise track of the late 1990s and early 2000s (Figure 2) 

is a high priority for the oceanographic and sea ice 

Table 1. Description of sample cruise tracks. The minimum time required is referenced to the time required to complete the 

basic crossing for either the Atlantic-Pacific transit or the ice camp transit and gives the additional time necessary to complete 

the route, with no additional time dedicated to the collection of SCICEX data. Although the track descriptions generally 

start from the Atlantic Ocean, all of these tracks could be performed in either direction.

Cruise 

Track

Sampling 

Corridor Track FigureNumber

Min Time

Required Description

Atlantic-Pacific Transits

Direct

AtlanticPacific 

Crossing 

3 none Direct transit between Atlantic and Pacific oceans

1 North Pole 5a 2 days

A track roughly parallel to the recent SCICEX track but displaced 

toward the Canadian side of the basin so as to pass through 

the North Pole

1 Recent 

SCICEX 5b 3 days

Designed to replicate the cruise tracks conducted on several of the 

dedicated SCICEX cruises. The endpoints of this track were initially 

selected in the mid-1990s to support the Acoustic Thermometry of 

Ocean Climate (ATOC) program.

2 and 4 Eastern Offset 5c 1 day

Enters the Data Release Area at about 60°W (north of the Lincoln 

Sea), crosses to the North Pole to the Gakkel Ridge, then makes a 

perpendicular crossing of the Makarov Basin. The first leg of the track 

is designed to collect ice data along a line roughly perpendicular to the 

ice thickness gradients.

2, 3, and 5 Cross Canada 

Basin 5d 2.5 days

After passing though the North Pole, this track hugs the Canadian 

boundary of the Data Release Area, then continues eastward across the 

breadth of the Canada Basin before exiting.

Ice Camp Transits

Direct 

Ice Camp

Crossing

3 none Direct transit between Atlantic or Pacific Ocean and the 

Beaufort Ice Camp

1 North Pole 5a 0.5 days Similar to Atlantic-Pacific North Pole track 

1 Recent 

SCICEX 5b 1 day Similar to Atlantic-Pacific recent SCICEX track 

3 Canadian 

Margin 5e 0.5 days Hugging the Canadian boundary of the Data Release Area from the entry point to the southern Beaufort Sea
9

communities. Repeating this transect at 5–10 km lateral offsets will satisfy most oceanographic objectives 

while adding new bathymetric lines for the marine 

geology community. 

Although not a part of the SCICEX program, the 

SCICEX SAC acknowledges that the ice camps established in the Alaskan Beaufort Sea as part of the Navy’s 

(typically biannual) ICEX offer an important opportunity to conduct focused experiments. Unique to 

these ice camps, and in contrast to the transits, is the 

chance for advanced and coordinated planning. Thus, 

studies can be designed to explore new or improved 

techniques for submarine-based sampling. There is 

frequently an unclassified extension to the ice camp 

that facilitates research by civilian scientists. In these 

cases, the Navy transfers operation of the established 

ice camp over to the organizations funding the research 

(e.g., NSF, NASA). This transfer is made in recognition 

that the ice camp is a valuable platform for conducting 

process-oriented investigations and testing new datacollection technologies. For example, during 2007, the 

unclassified extension of the ICEX ice camp was successfully used to test the integration of various aboveice and below-ice systems for measurement of sea ice 

thickness (Hutchings et al., 2008). Researchers interested in pursuing these opportunities should contact 

appropriate agency program managers.

In support of developing and maintaining a sustained 

AON, the SCICEX planning recommendations seek 

to complement and contribute to other observing 

system components. For instance, SCICEX sampling 

in and around the North Pole (corridors 1 and 4) can 

augment ice and ocean observations made as part of 

the North Pole Environmental Observatory program 

(http://psc.apl.washington.edu/northpole). Sampling 

along the Atlantic ends of corridors 1 and 4 complements the work of the Freshwater Switchyard Project 

(http://psc.apl.washington.edu/switchyard/index.

html), aimed at improving understanding of freshwater circulation in the region between Ellesmere Island 

and the North Pole. Studies conducted as part of the 

Beaufort Gyre Exploration Project (BGEP, http://www.

whoi.edu/beaufortgyre/index.html) will benefit from 

SCICEX measurements made in the Canada Basin 

(corridors 1, 2, 3, and 5). 

The inherent flexibility of the sampling recommendations laid out in the SCICEX Science Plan, Part 1, lends 

itself to successfully coordinating with other existing 

AON elements. For example, where an existing AON 

program samples within a specific geographic region 

during summer, the SCICEX program could provide 

complementary sampling during spring conditions. If 

that summer AON sampling program were to end, the 

SCICEX program could refocus its priority to extend 

the summertime sampling in that region. 
10

Figure 5. Example cruise tracks. Times for each of these tracks are 

given in Table 1.
11

SAMs Sampling Priorities 

and Recommendations

Overarching

The overarching recommendation is that the ASL seek 

additional SCICEX sampling time from the operational 

Navy to collect measurements within specific corridors 

of interest (Figure 4). The scientific justifications and 

prioritizations, which form the core of this SCICEX 

Science Plan, are intended to give guidance to ASL 

in negotiating and planning for the additional sampling time to collect data along specific tracks within 

these corridors. 

It is also a high priority that SCICEX sampling become 

a routine part of the direct Arctic crossing transits 

(Figure 3) in the event that there is not sufficient time 

to deviate to one of the more desirable tracks. The 

Atlantic-Pacific transit crossing line is the shortest 

route between the Atlantic and Pacific oceans and is 

anticipated to be routinely occupied. The direct transit in support of ice camp operations is another track 

that will be routinely occupied, albeit at an expected 

frequency of only once every two years. Taken together, 

these tracks traverse most of the major Arctic Ocean 

bathymetric and ocean circulation features within the 

SCICEX Data Release Area.

Ice Draft Profiling

Background

Profiles of sea ice draft obtained from the upwardlooking sonars of submarines transiting the Arctic 

Ocean have provided the bulk of our current knowledge 

of ice thickness over the Arctic basin. Early analyses 

of ice draft data compiled from one or more cruises 

revealed aspects of spatial ice thickness variability 

(Bourke and Garrett, 1987; Bourke and McLaren, 1992). 

These early analyses also initiated discussions about the 

possible thinning of the ice cover, even in the face of a 

limited knowledge of natural variability (McLaren et al., 

1990; Wadhams, 1990; Shy and Walsh, 1996). 

The advent of the SCICEX program in the 1990s 

greatly expanded the available unclassified ice draft 

data (Rothrock et al., 1999a) and allowed comparison 

of 1990s ice drafts with earlier previously published 

data (Rothrock, et al., 1999b; Yu et al., 2004). These 

analyses established that, indeed, the ice had thinned 

significantly within the Data Release Area between 

1950–1970 and the 1990s. With the subsequent 

declassification of ice draft data collected on many 

earlier cruises, as well as the availability of some ice 

draft data collected by submarines from the United 

Kingdom, interannual changes have been examined 

in greater detail. As a result, rapid decreases in thickness have been confirmed in some regions of the Arctic 

(Wadhams and Davis, 2000; Tucker, et al., 2001). 
12

The recent digitization of analog recordings of ice draft 

has generated a great deal more data (Wenshahan 

and Rothrock, 2005; Rothrock and Wensnahan, 2007; 

Wensnahan, et al., 2007), which has allowed even more 

detailed analyses of ice draft spatial distribution as well 

as annual and interannual variability. Rothrock et al. 

(2008) found a marked decrease in mean ice draft from 

1980 to 2000, with the largest rate of decline occurring 

in 1990 and a lesser rate toward the end of the period. 

However, Kwok and Rothrock (2009) found even larger 

annual declines during the period 2003–2008 using ice 

thickness derived from satellite altimetry to extend the 

submarine data record.

It is likely that the submarine will continue to play a 

key role in an integrated strategy for monitoring ice 

thickness. Kwok et al. (2009) demonstrated that satellite altimetry could provide reasonable estimates of 

large-scale ice thickness by comparing the altimetry 

to submarine and moored sonar records of ice draft. 

This development is timely given the more recent 

large reductions in ice extent and thickness (RichterMenge et al., 2008). Ideally, it will become more 

commonplace for SCICEX-derived ice thickness data 

to be effectively combined with data collected from 

satellite-borne instruments (e.g., Kwok et al., 2007, 

2009; Nghiem et al., 2007; Giles et al., 2008), moorings (e.g., Melling et al., 2005), ice mass balance buoys 

(Richter-Menge et al., 2006), and computer model simulations (e.g., Rothrock and Zhang, 2005; Maslowski 

at al., 2007; Lindsay et al., 2009). Each sensor platform has its own unique capabilities and limitations. 

Although the capability of satellite-borne instruments 

to measure ice thickness variability over large regions 

has improved, submarines continue to provide the 

most accurate, detailed, large-scale thickness information. Although the submarine data are recognized to be 

temporally and spatially limited, they will continue to 

provide critical monitoring of the ice pack and, hence, 

data that are key for the validation and calibration of 

the satellite data and model output. Conversely, satellite 

data and model output can be used to identify regions 

of particularly high importance for sampling during 

a SCICEX SAM.

Sampling Recommendations

The ice draft profiling strategy aims to (a) collect highquality information to add to the existing archive of 

ice draft data and (b) continue to monitor the ongoing 

dramatic changes in ice thickness distribution. The 

areas identified as high sampling priorities include 

regions that have been heavily profiled in the past, 

areas where significant changes in ice thickness have 

taken place or appear imminent, and regions where 

little is known about the ice thickness distribution 

because of data scarcity. These sampling regions, in 

priority order, are: 

1. The North Pole region (within corridors 1 and 4)

2. A north-south track extending from near or at 

the North Pole south to near the coast of Alaska 

(corridor 1)

3. Two tracks crossing the release area from near the 

Canadian Archipelago to the Russian side of the 

box, nearly perpendicular to the north-south track 

(corridors 4 and 5) 

4. A track adjacent to the Canadian Archipelago 

(corridor 3)

The North Pole area is selected as the highest priority 

sampling region because it has the greatest historical coverage of ice profile data, and future submarine 

transits are likely to pass near it. The sampling preference is for two 50-km legs, one passing to either side of 

the North Pole.

Although ice near the North Pole is of interest from 

a historical perspective, the central Canada Basin 

(central and northern Beaufort Sea) has undergone 

some of the most significant changes in ice cover, 

within the SCICEX Data Release Area, since the late 

1980s. Satellite remote sensing and modeling results 

indicate that the Arctic has experienced a significant 

decline in the amount of perennial ice (Rigor and 

Wallace, 2004; Nghiem et al. 2007), due in large part to 

changes in atmospheric circulation that have weakened 

or interrupted the Beaufort Gyre (Tucker, et al., 2001; 

Pfirman et al., 2004; Rigor and Wallace, 2004), and 
13

subsequent purging of much of the older ice through 

Fram Strait. A high priority, then, is to provide the 

most frequent sampling possible to assess the relative volume of older, thicker ice. A track extending 

from the region of the North Pole southward toward 

Alaska, using either the North Pole transect (Figure 5a) 

or the traditional SCICEX transect (Figure 5b, used 

frequently on SCICEX cruises in the 1990s), will cross 

this important region. 

Another high-priority region for sampling extends 

across the Canada Basin from the Canadian side to the 

Russian side of the SCICEX box, essentially bisecting 

the Canada Basin. These tracks cross some of the thickest ice in the Arctic, near the Canadian Archipelago, 

and traverse the region of transition from multiyear ice 

in the Beaufort Gyre to younger ice originating in the 

Chukchi and East Siberian seas. The track along the 

Data Release Area’s Canadian margin provides information about this historically thick ice region, where 

there are currently very limited data.

For consistency and comparison with prior data, it is 

recommended that ice profiles be collected over 50-km 

sample lengths along all sample transects while operating at a submarine depth of approximately 122 m 

(400 ft) and a speed of 14 kt. Most submarine ice draft 

data analyses have used a 50-km-long sampling interval for reporting ice draft statistics, and this interval 

has become the de facto standard (Rothrock et al., 

2008). With regard to U.S. Navy submarine operations, 

the optimal ice draft data are obtained when the ship 

operates at slower speeds and shallower depths. In the 

past, high-quality data have been obtained at operating 

depths and speeds standardized to about 122 m and 

14 kts, respectively.

Sampling strategies are identified based on the time 

available for ice profiling and on the geographic 

priorities (Appendix A). Take, for instance, the ice 

sampling recommendations made for the high-priority 

corridor 1. Even with no additional time available, 

continuous sampling is recommended with the expectation that useful data will be obtained even at the 

greater depths and higher speeds likely to be used 

when the submarine is transiting the Arctic. Given a 

half day of additional sampling time, the preference 

is to slow the submarine to 14 kt and come to a depth 

of 122 m for sampling along two 50-km segments to 

either side (Atlantic and Pacific) of the Pole and six 

50-km segments evenly distributed along the northsouth track within corridor 1. With more time available, more 50-km segments can be sampled. The 

second priority for ice draft data collection is the 

cross-Canada Basin track encompassed by corridor 5. 

Appendix A also shows the sampling strategies for 

other geographic regions. If different tracks are chosen 

to satisfy the different scientific disciplines, the ice 

sampling strategies spell out how the ice profiling segments should be allocated.

Methods and Implementation

U.S. Navy submarines routinely obtain observations 

of sea ice draft in the Arctic Ocean using upwardlooking sonar. These operational instruments are used 

to ensure safe maneuvering of the submarine, and were 

not designed to collect scientific data. Draft measurements are made by a sonar transducer mounted in 

the submarine’s sail. A highly focused beam of sound 

(2–3° beam width) is transmitted upward through the 

water column, reflecting off the bottom of the sea ice 

and returning to the transducer. The system uses the 

signal travel time and an assumed sound speed to estimate the distance from the transducer to the ice. The 

ice draft is then calculated as the difference between 

the depth of the ship, as measured by a pressure transducer, and the distance to the ice. It is this approximate 

draft that is recorded by the ship system.

The data are recorded either digitally or on analog 

paper charts, or a combination of the two. The digital 

recording system uses a set of hard-coded thresholds to determine whether the signal has sufficient 

strength and duration to count as a valid return, in 

which case the leading edge of this return is recorded. 

The recorded draft is therefore the deepest ice from 

the return and is referred to as the “first return.” The 
14

analog charts in the ASL archive have been processed 

to approximate the equivalent of a digital first return 

product (Wensnahan and Rothrock, 2005).

The draft is measured and recorded about six times 

per second. At typical submarine speeds, this recording frequency provides a spatial profile of draft with a 

data spacing of about 1 m for digital data. Overwriting 

of successive measurements on the paper chart limits 

these data to a resolution of about 1 ping per second (at 

14 kt, 1 ping per second translates to a ~7-m spacing).

A significant amount of data in the NSIDC archive was 

collected at greater depths and higher speeds than the 

typical 122 m and 14 kt, respectively. The ICEX-09 submarine exercises in the southern Beaufort Sea during 

March 2009 provided an opportunity to make repeated 

submarine runs at different depths and speeds over the 

same underice track. Ongoing analyses will determine 

the quality of the ice draft data collected at different 

depth/speed combinations and the impact of acquiring 

data at greater speeds and depths than in the past.

Raw data are normally designated as “classified” by 

the Navy and are then archived at ASL. Processing of 

the raw data includes: (a) editing to remove spurious 

points, (b) calibrating the draft to sea level, (c) tying 

the draft to navigation data, and (d) stripping out segments during submarine maneuvers when the data 

are difficult or impossible to interpret. The result is a 

sequence of profiles, varying in length from a few to 

several hundred kilometers, along the submarine track.

Ice draft data are taken as a normal part of ship operations and are available for the entire cruise. To clear 

the classified data taken during normal operations for 

public release, times are rounded to the nearest third 

of a month and positions are rounded to the nearest 

five minutes of latitude and longitude. These constraints are relaxed during SCICEX missions, when the 

data include accurate (unrounded) time and position 

information. All data are reviewed by ASL and are 

approved for public release as unclassified. Data have 

been released, with very few exceptions, only within 

the SCICEX Data Release Area, which covers roughly 

half of the central Arctic Ocean (Figure 1). Draft data 

are now publicly available from some 40 cruises from 

1975 to 2000, covering over 120,000 km of track. Draft 

data from two cruises in 2005 have been processed 

and will be archived at NSIDC. Because the submarine 

routinely collects ice draft data, it remains possible for 

additional data to be made available via the funding of 

independent proposals. All processed ice draft data are 

archived for public use at NSIDC (go to http://nsidc.

org/data/g01360.html).

As explained in Rothrock and Wensnahan (2007), 

the major sources of error in the draft measurements 

include: (a) inaccuracy in the selection of open water 

for calibration, (b) variation in the upward-looking 

sonar power and gain settings, which affect thresholding, and (c) bias due to the finite footprint size of the 

sonar system. Errors due to submarine orientation 

(e.g., pitch, roll, yaw), which occur primarily when 

the submarine is maneuvering, are removed from the 

record during processing. The standard deviation of 

the error in the draft measurement is 22 cm. This number estimates the repeatability and comparability of 

draft measurements by U.S. Navy submarines. The bias 

in the submarine-based measurement of ice draft with 

respect to the actual draft is +29 ± 12 cm. 

Ocean: Hydrography

Background

During the 15-year period since the beginning of the 

SCICEX program, our knowledge of the circulation 

and distribution of water mass properties within the 

upper layers of the Arctic Ocean has increased significantly. Yet, due to the Arctic’s many scales of variability 

and continuing inaccessibility, we are still hard pressed 

to provide details on the variability of many of these 

features. CTD and expendable CTD (XCTD) data collected during the six dedicated-science SCICEX cruises 

(1993, 1995–1999) contributed early to the awareness 
15

of variability in the peripheral flow of Atlantic Water 

(AW). In particular, they revealed the increasing 

temperature in the early 1990s of the core Atlantic 

Water layer flowing along the Lomonosov Ridge 

(Morison et al., 1998; Gunn and Muench, 2001) and 

large-scale variations in the salinity of the halocline in 

the Amundsen and Makarov basins (Steele and Boyd, 

1998; Boyd et al., 2002). These studies made use of the 

submarine’s capability to make synoptic basin-spanning observations of the upper ocean temperature and 

salinity fields. The submarines were also used within 

the dedicated science program to conduct focused 

studies in specific regions and on specific processes, 

such as the Canada Basin eddy study of Muench et al. 

(2000). These experiments demonstrated the value of 

externally mounted chemical sensors in conditions 

where temperature and salinity alone are not sufficient 

to distinguish water mass origins (Guay et al., 1999). 

XCTD observations contributed to studies that focused 

primarily on upper ocean water analysis (e.g., Smith 

et al., 1999). Accuracy of the XCTD salinities were 

considered insufficient, however, to contribute significantly to the understanding of deep variability, such as 

revealed in Smethie et al.’s (2000) study of ventilation of 

Canada Basin intermediate waters. 

Whereas several early analyses by SCICEX-funded 

investigators focused on upper ocean changes through 

comparison of the SCICEX data with climatic data, 

more recent analyses (often conducted by the broader 

oceanographic community) have treated the SCICEX 

archive as one of several contemporary data sources. 

These subsequent studies, which have focused on 

several different aspects of upper ocean circulation and 

water mass distribution in various parts of the Arctic 

Ocean, illustrate the value of the SCICEX data to the 

oceanographic community. For example, Kikuchi et al. 

(2004) combined SCICEX data with icebreaker and 

drifter data to examine the distribution of convectively formed lower halocline water in the Amundsen 

and Nansen basins. Kikuchi et al. (2005) also used 

data from this suite of platforms to demonstrate the 

cyclonic circulation of AW on the Makarov Basin side 

of the Lomonosov Ridge and the increased time lag of 

AW warming there relative to the circulation of AW on 

the European side of the ridge. Shimada et al. (2004) 

used SCICEX, icebreaker, and drifter data from the 

Canada Basin to describe the movement of the 1990s 

AW warm temperature anomaly along the base of 

the Mendeleyev Ridge and Chukchi Plateau and into 

the Beaufort Sea. Woodgate et al. (2007) analyzed the 

structure of intrusions in the core of the Atlantic layer 

to extract details on the flow of Atlantic Water over the 

base of the Mendeleyev Ridge and Chukchi Plateau, but 

found that salinity spiking in the XCTD data marginalized the SCICEX contribution to the analysis. Steele 

et al. (2004) used SCICEX and other data to investigate 

the 1990s distribution of water masses of Pacific origin 

in the central basin and its relationship to atmospheric 

forcing and ice motion. Shimada et al. (2006) used 

SCICEX and other data from the 1990s to consider 

the positive feedback of Pacific Water temperature 

on sea ice concentration in the Beaufort Sea through 

increased coupling of wind forcing to the ocean.

As the SCICEX data archive has grown, it has played a 

greater role in climate and modeling studies. For example, the cross-basin synoptic XCTD sampling of the 

dedicated-science cruises provided much of the 1990s 

data used in Polyakov et al.’s (2004) analysis of multidecadal variability of AW core temperature. Recently, 

the SCICEX XCTD data have been used as a point of 

comparison for numerical modeling studies to validate 

model results of temperature and salinity distributions 

(e.g., Karcher et al., 2003), and to evaluate the dynamical implications of mixing parameterization in Arctic 

regional models (Zhang and Steele, 2007). 

Sampling Recommendations

The hydrographic sampling program recommended 

here is intended to enhance and broaden the data 

archive that has made possible studies such as those 

briefly described above. In particular, the sampling 

should contribute observations that allow monitoring 

and detection of: 
16

•	 Movement of the upper ocean water mass boundaries, and variability of the water mass characteristics

•	 Variability of the temperature and pathways of upper 

ocean currents

•	 Variability of upper ocean freshwater content (salinity deficit) and static stability

These general objectives will be addressed in the SAMs 

by obtaining vertical profiles and continuous horizontal time series of temperature, salinity, and, as possible, 

other variables of interest. The following list of specific 

sampling objectives is in order of decreasing priority.

1. The existing time series of across-basin SCICEX 

transects have contributed to understanding AW 

temperature and salinity distribution variability 

along the peripheral and along-ridge pathways of 

the central basin, and the static stability variability 

of the Amundsen and Makarov basins’ upper layers. Continuation of this time series is the highest 

sampling priority, and can best be accomplished by 

repeating the canonical across-basin transects of 

the late 1990s/early 2000s (sampling corridor 1 in 

Figure 4; cruise tracks a and b in Figure 5). 

2. Temperature and salinity variability along transport 

pathways from the Russian margins to the central 

basins can be sampled on cruise tracks that cross 

the Lomonosov Ridge (sampling corridor 2; cruise 

track c) and the Mendeleyev Ridge (sampling corridors 2 and 5; cruise tracks c and d). These cruise 

tracks will contribute data that are less directly comparable to the previous SCICEX data, but that are 

from a region of the Arctic that historically has been 

difficult to access, and remains difficult to sample 

even with icebreaker-deployed, ice-based, autonomous sampling systems. 

3. Freshwater and heat content variability in the upper 

layers of the Beaufort Gyre can be sampled along 

cruise tracks that pass through the Canada Basin 

(sampling corridors 1, 3, and 5; cruise tracks a, 

b, d, and e). Model results (W. Maslowski, Naval 

Postgraduate School, pers. comm., 2010) suggest that 

the Chukchi Plateau (aka Chukchi Borderlands) is 

presently the region of strongest influence of warm 

summer Pacific Water on sea ice. This region will be 

sampled along cruise tracks at the Alaskan end of 

corridors 1 and 2.

4. Variability in the location and movement of the 

Atlantic/Pacific front separating Atlantic and Pacific 

water mass assemblies can be sampled along cruise 

tracks that pass through the Makarov Basin (sampling corridors 2 and 5; cruise tracks c and d).

5. Variability in the pathway followed by Pacific Water 

in flowing from the Arctic Ocean to the North 

Atlantic can be sampled along tracks that pass 

through the western Amundsen Basin (sampling 

corridor 3; cruise tracks d and e).

6. The rates and impact of mixing of AW into ambient waters of the Canada Basin can be addressed 

through sampling along cruise tracks that cut across 

the AW pathway near the base of the Mendeleyev 

Ridge, the Chukchi Plateau, and the Chukchi Sea 

edge of the Data Release Area (sampling corridors 2 

and 5; cruise tracks b, c, and d). 

The hydrographic sampling priorities shown in the 

Planning Matrix (Appendix A) indicate regions along 

the cruise tracks where XCTD deployments should be 

concentrated, the numbers of additional probes that 

could be used for the increments of sampling time 

shown, and the desired horizontal resolution of vertical 

profiles along each transect. It is noted that many of the 

objectives identified above will be served by sampling 

along the direct Atlantic-Pacific transit, and some will 

be served by sampling along the direct ice camp transit. 

Although sampling along the direct transits will not 

meet the objectives as well as the tailored sampling 

corridors and cruise tracks, we expect that the direct 

transit opportunities may be more frequent and thus 

may represent the best opportunities to increase the 

archival database.

Methods and Implementation

The hydrographic sampling program will take advantage of the submarine’s capability to make two types 

of measurements: (1) vertical profiles of conductivity, 

temperature, and depth, and (2) along-track time series 
17

of conductivity, temperature, and depth, and, as possible, other relevant chemical variables at the submarine’s operating depth. 

Vertical profiles will be obtained using the most current, vetted version of under-ice submarine-launched 

XCTD probes. The XCTDs are launched from the 

operating depth of the submarine, rise toward the surface, and then invert and profile downward, currently 

to a maximum depth of 1000 m. Each XCTD deployment requires about 45 minutes for the submarine to 

complete. To date, the dedicated-science missions and 

SAMS have largely made use of an analog probe that 

is no longer available. In the near future, SAM cruises 

will make use of TSK/Sippican digital XCTD probes 

that are identical to the XCTD probes presently available for use from surface vessels, but which are packaged for use by submarines and employ launch and 

data acquisition systems that are unique to submarines. 

Sippican specifies the accuracy (and resolution) 

of the XCTD as ± 0.02 (0.01) o

C for temperature, ± 0.03 (0.017) mS/cm for conductivity, and 

± 2% or 20 m (0.17 cm) for depth, where depth is not 

directly measured but is inferred from the elapsed 

time and a known rate of descent. Testing of the 

TSK/Sippican XCTDs was conducted by ASL and Navy 

personnel during the ICEX-09 submarine exercises 

in the southern Beaufort Sea during March 2009. 

Testing consisted of comparing CTD casts conducted 

at the ICEX-09 ice camp to XCTDs launched nearby 

from USS Helena (SSN 725). Preliminary analysis of 

the test results show that the probes suffered a higher 

failure rate than experienced with analog probes of the 

dedicated-science program of the 1990s, which had 

typical success rates of >90%. Twelve of the 16 probes 

(75%) tested during ICEX-09 returned profile data, all 

of which provided accurate values of temperature and 

salinity from the base of the mixed layer to the maximum depth sampled. None of the probes sampled to 

a depth greater than 600 m (design maximum depth 

is 1000 m), and the maximum depth for seven of the 

probes was less than 400 m. Notably, the raw profile 

data from these probes did not exhibit salinity spiking, 

such as was typical of the earlier analog probe data 

(Woodgate et al., 2007). In summary, the ICEX-09 

XCTD test revealed that: (1) TSK/Sippican XCTD 

probes yield data of quality that will be useful to the 

SCICEX program, but (2) the failure rate is high, and 

(3) the failure to achieve data to the design depth is 

an unresolved issue. The SCICEX SAC is planning 

additional testing to resolve the issues of reliability and 

maximum sampling depth prior to routine XCTD use 

on SAM cruises.

Although the accuracy of the digital XCTDs is better 

than that of the analog probes of the 1990s (Gunn and 

Muench, 2001), the salinity accuracy (approximately 

0.04 psu; Mizuno and Watanbe, 1998) is still significantly worse than industry-standard CTDs and is not 

considered sufficient to resolve much of the anticipated 

salinity variability below the halocline. The XCTD 

probe accuracy should be sufficient to resolve the water 

mass differences and much of the variability at shallower depths, as well as temperature changes throughout much of the upper ocean. The most significant 

improvement resulting from the introduction of the 

digital XCTDs is the reduction of salinity spiking due 

to the improved matching of the response times of 

temperature and conductivity sensors. This improvement should, for example, increase the suitability of the 

SCICEX data for analyses conducted in the AW intrusions (e.g., Woodgate et al., 2007). Because of thermal 

mass issues directly following launch from the submarine, the XCTDs do not typically obtain valid data 

shallower than 15–20 m and, therefore, may not be 

suitable for determining freshwater and heat balance in 

the uppermost mixed layer.

Time series at the depth of the submarine will be 

obtained using a pumped CTD that will be mounted 

in a free-flood space in the submarine sail, typically 

about 15 m (50 ft) above the keel depth, and plumbed 

to the exterior of the submarine. At present, Sea-Bird 

Electronics model SBE-19 and SBE-49 CTDs are the 

only units that have been approved for use on the 

submarine classes that will be used for SAMs. The 

manufacturer’s specified accuracies (and resolutions) 
18

for the SBE-19 are ± 5 x 10-3 (1 x 10-4) °C for temperature and ± 7 x 10-3 (0.7 x 10-3) psu for salinity. 

Values for the SBE-49 are ± 2 x 10-3 (1 x 10-4) °C and 

± 4 x 10-3 (0.7 x 10-3) psu, respectively. The model 

SBE-19 CTD can provide power to and accept signals 

from external sensors (the current model, SBE-19plus 

V2, has six A/D and one RS-232 input channels), 

whereas the SBE-49 CTD does not accept any auxiliary 

signals. Thus, opportunities for addition of other sensors (e.g., dissolved oxygen, fluorescence) for continuous measurement will more easily arise on SAM 

cruises in which model SBE-19 CTDs are used. At 

present, ASL plans to use SBE-19 CTDs during SAMs 

whenever possible. The addition of auxiliary sensors 

may require a hardware approval (TEMPALT) from 

the Navy. A separate TEMPALT would be required for 

each class of submarine on which the hardware will 

be used. This process is costly and time-consuming. 

Members of the science community interested in the 

inclusion of additional underway sampling sensors or 

systems, whether commercial-off-the-shelf or custom 

designed, should consult the ASL Technical Director 

for advice and recommendations prior to submitting 

proposals that include such sampling.

The SCICEX underway CTD data have been used successfully to identify water mass boundaries (Morison 

et al., 1998, Muench et al., 2000) when the submarine 

was traveling with the CTD at depths ranging from 

104 m to 218 m. When crossing the ridges and slopes 

along which the peripheral currents flow, it is considered preferable for the submarine to operate close to 

the maximum operating keel depth of 244 m (800 ft) to 

be as close as possible to the depth of the AW’s warm 

core and to avoid, insofar as possible, the strong vertical salinity gradients associated with the halocline. The 

underway CTD typically has been mounted in the top 

forward part of the sail, and plumbed to the outside 

with as short a hose as feasible to minimize the flushing 

time. Correlation with vertical profile data led Morison 

et al. (1998) to conclude that the externally pumped, 

sail-mounted underway CTD drew water from about 

20 m beneath the CTD depth due to flow distortion 

around the submarine.

Auxiliary data were recorded by the underway CTD 

system during some of the dedicated science cruises 

of the 1990s, conducted aboard the now-retired 

Sturgeon (637) Class submarines. As an example of the 

utility of these measurements, Muench et al. (2000) 

used dissolved oxygen data, along with temperature 

and salinity, to distinguish between eddy and ambient water in the interior of the Canada Basin. It is well 

known that temperature and salinity alone do not 

provide sufficient information to distinguish between 

water masses in the upper Arctic Ocean (McLaughlin 

et al., 1996; Macdonald et al., 1996; Swift et al., 1997; 

Wheeler et al., 1997). Consequently, sensors that can 

provide reliable data on concentrations of O2, dissolved 

organic carbon (DOC), NO3, and other nutrients 

should be incorporated into the time-series measurement program as they become available (see Table 2). 

As mentioned earlier, the Navy will require a 

TEMPALT prior to introduction of any new sampling 

sensor or system for each class of submarine on which 

it will be used. Interested parties should contact the 

ASL Technical Director for advice and recommendations regarding the process of adding sensors.

Ocean: Chemistry

Background

Chemical measurements have been used extensively 

to investigate physical and biological processes in the 

Arctic Ocean. Numerous measurements were made on 

the SCICEX cruises of the 1990s, during which circulation patterns and time scales were investigated using 

the transient tracers tritium, 3

He, chlorofluorocarbons 

(CFCs), and 129I. Smethie et al. (2000) showed from tritium, 3

He, and CFC measurements made on the 1996 

SCICEX cruise that the central Canada Basin is ventilated with Atlantic Water on a time scale of one to two 

decades and that the oldest intermediate water in the 

Canada Basin was located in the northern end of the 

basin. There are two layers of Atlantic Water: the Fram 

Strait Branch, which is responsible for the temperature 
19

maximum beneath the halocline found throughout the 

Arctic Ocean, and the Barents Sea Branch, which is 

denser and underlies the Fram Strait Branch. Smethie 

et al. (2000) also showed that the Fram Strait Branch 

was diluted by a factor of five due to exchange with 

shelf water along its flow path, but that the deeper 

Barents Sea Branch (core depth about 800 m) was 

diluted by only a factor of about two. Using 129I data 

collected from the 1995 and 1996 SCICEX cruises, 

Smith et al. (1999) showed that the intermediate water 

(Barents Sea Branch) in the central Canada Basin was 

recently ventilated and that the ventilation time for the 

northern Canada Basin was in agreement with Smethie 

et al.’s (2000) results. They estimated the transit time 

for upper Atlantic Water (Fram Strait Branch) from the 

Norwegian Current was about seven years and slightly 

less for the overlying halocline water.

Exchange between the continental shelf and interior 

of the Arctic Ocean has been investigated from naturally occurring chemical substances measured on 

the SCICEX cruises. Guay et al. (1999) used salinity, 

chlorophyll a, barium, total organic carbon (TOC), and 

DOC to identify locations where river water crosses 

the continental shelf break between the Alaskan coast 

and the Laptev Sea to enter the interior of the Arctic 

Ocean. River water was identified as local minima 

in salinity and maxima in barium, TOC, and DOC. 

Kadko and Aagaard (2009) used the 228Ra:226Ra ratio 

to identify shelf water in the interior of the Arctic 

Ocean from measurements on the 2000 SCICEX cruise. 

Water in contact with the extensive shelf sediments 

acquires a radium signal with a high 228Ra:226Ra ratio. 

At 132-m depth, the 228Ra:226Ra ratio varied by a factor of about seven along a line extending through the 

center of the Canada Basin from Alaska to the Gakkel 

Ridge. The ratio was lowest between Gakkel Ridge and 

Lomonosov Ridge, indicating relatively little shelf water. 

The ratio varied by a factor of three in the Canada 

Basin, suggesting that the inflow of shelf water to the 

interior was episodic in space and time. 

One mechanism for shelf basin exchange is eddies. 

As mentioned in the section on ocean hydrography, 

on the 1997 SCICEX cruise, Muench et al. (2000) 

observed such an eddy and mapped its temperature, 

salinity, and velocity fields. They also measured a suite 

of tracers inside and outside the eddy. It was determined from 18O and tritium that the origin of the eddy 

was the Alaska Chukchi coast and that it was less than 

two years old. 

More recently, SCICEX data have been combined with 

data from other icebreaker-based cruises. For instance, 

Tanhua et al. (2009) combined SCICEX CFC data with 

CFC data collected from icebreaker cruises between 

1983 and 2005 to calculate the transit-time distribution 

for water to flow from its sources to the Arctic Ocean 

interior. From this, they calculated the anthropogenic 

CO2 inventory. The amount is 2.5–3.3 Pg-C, which is 

about 2% of the total in the world ocean. Relative to 

its volume, the Arctic Ocean takes up two times more 

than the average of the global ocean.

The Arctic Ocean is sensitive to the global rise in 

temperature and atmospheric carbon dioxide. One 

response has been a steady decrease in sea ice extent 

during summer. As the amount of open water increases, 

there is expected to be biogeochemical consequences, 

which could be documented along the SAM submarine 

tracks. Also, as a result of the enhanced CO2 uptake and 

the relatively low buffer capacity afforded by river and 

ice-melt-freshened Arctic Ocean surface waters, the 

Arctic is particularly vulnerable to ocean acidification. 

Models suggest that uptake of anthropogenic CO2 by 

Arctic Ocean surface waters will drive the largest and 

fastest pH decreases in all the world’s oceans (Steinacher 

et al., 2008). This pH decrease has already and will 

continue to increase sound transmission in the circa 

10 kHz frequency range (Hester et al., 2008). The implications of decreasing pH for organisms, particularly 

those that form calcium carbonate shells, are likely to 

be important and are only beginning to be understood 

(Doney 2006; Doney et al., 2009; Orr et al., 2005, 2009). 

With appropriate instrumentation, SCICEX SAMs can 
20

make a very important contribution to this issue by 

providing much-needed baseline data for relevant in 

situ sensed variables such as alkalinity, pH, and pCO2. 

Global warming will also cause other changes in Arctic 

Ocean biogeochemistry that can be documented by 

submarine-based observations. For example, warming 

is thought to be causing an increase in methane release 

from shelf sediments, which could be detected from 

collection of water samples for shore-based methane 

measurements along SAM submarine tracks. 

Sampling Recommendations

The chemistry program’s objectives, in 

priority order, are:

Table 2. Recommended water properties to measure on SCICEX Science Accommodation Mission cruises. Samples highlighted in 

blue can be made using current equipment and protocols. Others will require additional equipment or protocols, facilitated through 

independent proposals and coordination with the U.S. Navy Arctic Submarine Laboratory.

Sample Purpose Size Collection procedure On board processing Storage 

requirements

Underway continuous sampling via sensors

Temperature Core water property N/A Hull-mounted CTD None N/A

Salinity Core water property N/A Hull-mounted CTD None N/A

Oxygen

Water mass tracer; 

biological production 

and recycling

N/A Hull-mounted CTD None N/A

Nitrate

Water mass tracer; 

biological production 

and recycling

N/A Hull-mounted CTD None N/A

DOC Water mass tracer N/A Hull-mounted CTD None N/A

Alkalinity, pH, 

pCO2

CO2 uptake, ocean 

acidification N/A Pumped stream from

hull-mounted CTD None N/A

Chl a, variable 

fluorescence

Phytoplankton 

abundance, 

photosynthetic capacity

N/A Pumped stream from

hull-mounted CTD None N/A

Spectral 

radiometry, 

light 

scattering, and 

absorption

Chemical and biological 

properties (CDOM; 

overlying phytoplankton 

levels, particulate 

characterization)

N/A

Upward-looking sensors; 

pumped stream from hullmounted CTDNone N/A

Discrete water samples

Salinity

Core water property; 

calibrate salinty sensor 

on CTD

200 ml Rinse, fill, and cap a 200 ml 

glass bottle

Can be stored for shorebased measurement or 

measured on board with 

an Autosal

Room temperature

Oxygen

Water mass tracer; 

Biological production and 

recycling; calibrate O2

sensor on CTD

120 ml Rinse and fill 120 ml flask Add reagents, follow Winkler 

titration procedures

Room temperature 

covered with water 

for up to one day 

prior to titration

Chl a, HPLC 

pigments

Phytoplankton levels and 

community composition; 

calibrate Chl a

fluorometer on CTD

500 ml 

(Chl a

only) or 

1–3 L for 

HPLC

Chl a—filter and place filter 

into 10 ml 90% acetone; 

HPLC samples—freeze filter

Chll a can be measured in 

an on-board fluorometer 

or stored for shore based 

measurement like HPLC

–20°C, must not 

thaw (–80° if 

possible for HPLC)

Continued on next page...
21

1. Monitor the spatial and temporal (including seasonal) variability and longer-term trends of freshwater distribution and composition in the mixed layer 

and in the halocline.

2. Monitor the spatial and temporal (including seasonal) variability and longer-term trends of CO2, 

alkalinity, and pH in the mixed layer and in the 

halocline and compare these observations to variability and trends in plankton community structure.

3. Monitor the spatial and temporal variability and 

longer-term trends in the composition of the halocline and upper Atlantic layer.

4. Delineate circulation pathways for Atlantic and 

Pacific waters within the halocline and upper Atlantic 

layer, and estimate flow rates within the main upper 

ocean currents and transit times from source water 

regions to the interior.

Sample Purpose Size Collection procedure On board processing Storage 

requirements

Discrete water samples, continued

Flow 

cytometry

Microbial abundance 10 ml Rinse and fill 15 ml tube Add formalin and freeze

–20°C, must not 

thaw (–80° if 

possible)

Nutrients 

(PO4 , NO3 , 

SiO2)

Water mass tracers; 

biological production 

and recycling 

50 ml

Rinse, partially fill, and cap 

a 50 ml plastic tube; keep 

upright and ensure cap is tight

Quick freeze as soon as 

possible at –20°C

–20°C, must not 

thaw

18O Determine freshwater 

sources 100 ml Rinse, fill, and cap 100 ml 

glass bottles None Room temperature

Alkalinity CO2 uptake, ocean 

acidification 250 ml

Rinse and fill 250 ml glass 

bottle with screw cap leaving 

a 2 ml headspace

None Keep in dark at 

room temperature

SF6 , CFCs

Age information; 

calculation of 

anthropogenic CO2; 

water mass tracer

1–2 L

Rinse and fill a 250–500 ml 

glass stoppered bottle, insert 

glass stopper, place the bottle 

in a jar and fill the jar with 

sample water

None

Refrigerated at a 

temperature of 

0–2°C

Helium 

isotopes

Age information; 

water mass tracer

50 ml

Flush a 50 ml copper tube 

with the sample and crimp 

the ends of the tube with 

the water flowing; rinse the 

crimped ends with freshwater

None Room temperature

Tritium Age information; 

water mass tracer

500 ml Fill a 500 ml bottle without 

rinsing and cap None Room temperature

129I Circulation time of 

Atlantic water 1 L Rinse, fill, and cap a 1 L 

plastic bottle None Room temperature

Radium 

isotopes

Circulation of shelf water 

into the interior 130 L

Filter water through a 

cartiridge while the submarine 

is underway

Change cartiridge approx 

every three hours while 

submarine is underway

Room temperature

Table 2. Continued.
22

The freshwater volume and composition of the Arctic 

Ocean (mainly river runoff and sea ice melt) is expected 

to change as the sea ice continues to melt. To understand the causes of this change, freshwater volume and 

composition need to be documented as a function of 

time and space. This monitoring is best done by repeat 

measurements in specific regions. The highest priority for SCICEX SAM cruises is sampling corridor 1 

and the direct Atlantic-to-Pacific transit crossing line. 

Corridor 1 provides a long section extending across the 

entire Canada Basin and across the Amundsen Basin 

to the Gakkel Ridge (Figure 4), crossing many of the 

major circulation pathways of the upper waters of the 

Arctic Ocean and, thus, is well situated for monitoring 

changes in freshwater and circulation. The AtlanticPacific transit crossing line is the shortest route between 

the Atlantic and Pacific oceans (Figure 3) and will be 

the most frequently occupied line; thus it provides the 

opportunity for the most frequent sampling. All of the 

sampling corridors provide valuable information on 

the changing Arctic Ocean and should be sampled as 

the opportunity arises, but they have a lower priority. 

The same rationale holds for objectives 3 and 4, but for 

objective 2, all lines are of equal priority. With respect 

to timing, there are very few chemical data from the 

winter, so any winter cruises have a relatively high priority for all measurements.

Methods and Implementation

Table 2 provides the proposed chemical measurements, 

purpose of the measurements, and sampling and storage requirements. Some of the recommended measurements can be made with equipment that currently 

exists on the submarines. For instance, water temperature and salinity can be measured with the CTD that is 

now available. Most of the discrete water samples can 

be collected and then transferred to a shore-based lab 

for analysis. These samples basically require filling a 

sample container, without addition of chemicals, and 

storage at room temperature, refrigerated storage, or 

storage at -20°C. Some of the other measurements in 

Table 2 require additional equipment. If the underway 

CTD system includes a dissolved oxygen sensor (see 

discussion in ocean hydrography section regarding 

Sea-Bird Electronics model SBE-19 and SBE-49 CTDs, 

which are the only units that have been approved 

for use on the classes of submarine that will be used 

for SAMS), underway water samples will need to be 

collected periodically for calibration purposes. An 

oxygen titration system is needed for on-board measurement of oxygen in underway samples. A method 

needs to be devised for handling waste water, particularly for microplankton samples and radium isotopes. 

Scientific freezers are needed to store frozen samples. 

As previously discussed, independent proposals will be 

required to address these additional needs. 

The highest-priority measurements are salinity, 18O, 

nutrients, and dissolved oxygen. 18O has a much lower 

signal in river water than in seawater and sea ice melt, 

and thus allows the amount of these two freshwater 

sources to be estimated. Pacific Water has a different nutrient concentration than Atlantic Water. As it 

flows over the broad Chukchi shelf region, the nutrient 

and oxygen content is further modified by biological processes in the upper sediments, resulting in low 

oxygen concentration, high nutrient concentration, 

and a lower nitrate:phosphate ratio. Thus, nutrients and 

oxygen allow the amount of Pacific and Atlantic waters 

to be estimated. The water mass composition for the 

mixed layer and underlying halocline and intermediate water can be determined from temperature, salinity, and this suite of measurements. Of equal priority 

is the measurement of carbon chemistry parameters 

to determine if acidification is occurring and how it is 

affecting life in the Arctic Ocean. The transient tracers 

(tritium, 3

He, 129I, SF6, and CFCs) and radium isotopes 

have a slightly lower priority for measurement, but 

only because their sampling requires more time and 

storage space and may not be possible on some cruises 

where time is limited. 

Water sampling will be accomplished through the hull 

of the submarine. Salinity, nutrient, carbon chemistry, 

and 18O samples should be taken hourly on the transits to provide good horizontal resolution within the 

halocline and upper Atlantic Water along the transit 
23

lines. Radium isotopes should also be taken on the 

transits because they provide information on basin/

shelf exchange. Sampling involves continuously flowing water through a cartridge for several hours per 

sample while the submarine is underway. Vertical 

profiles of these parameters (except radium isotopes) 

and the transient tracers should be taken at the locations of 12 to 18 of the XCTD stations, roughly evenly 

spaced along the cruise track. Five depths between the 

surface mixed layer and the deepest operating depth 

of the submarine (~230 m) should be taken. Vertical 

sampling can be accomplished by a spiral station 

(i.e., a vertical excursion performed while executing 

a tight turn so as to minimize distance traveled) or by 

stair-step sampling at a speed of about 2 kts, so the 

vertical profile is confined to a small region. The stairstep method is preferred because a tight spiral vertical 

excursion of the submarine may result in significant 

vertical mixing of the water that will be sampled. It is 

very important to obtain a surface mixed layer sample 

at all XCTD stations to provide good spatial and 

temporal resolution of the distribution of freshwater 

components in the mixed layer.

This sampling scheme will also be useful for other 

chemical constituents that may be desired in the future.

Ocean: Biology

Background

Ocean biology is concerned with the interaction of 

marine organisms and their environment. These 

interactions are the basis for evaluating the response of 

marine biota to environmental and climate variations 

and are key aspects for predicting the health of marine 

populations as well as potential changes in biogeochemical cycles (Anderson and Kaltin, 2001; Smetacek 

and Nicol, 2005; Bluhm and Gradinger, 2008). All 

major taxonomic groups of organisms from microbes 

to fish, birds, and marine mammals are represented 

in the Arctic Ocean. The passive acoustic capabilities 

of the submarine fleet have not been used to observe 

marine mammals and fish, and would need specific 

authorization. Information from SCICEX has contributed significantly to the other aspects of biological/

environmental interaction in the Arctic, however, and 

the rapid evolution of in situ, biological sensing technologies, and molecular characterizations of collected 

material are well suited for more detailed observations 

on future SAMs. In addition, the parallel physical and 

chemical observations within SCICEX provide an 

important ecological context for the biological measurements. Several research issues, such as ice cover, 

Arctic Ocean circulation, river/shelf/basin exchange, 

and the role and extent of eddies, cut across several 

disciplines and help to define the processes by which 

Arctic biological systems respond to climate change. 

Biological sampling within the SCICEX program has 

focused mainly on microbial life due to its poorly 

understood diversity and its importance to the flows of 

nutrients and carbon (Falkowski et al., 2008). SCICEX 

sampling provided one of the first characterizations of 

the bacterial assemblages in the Arctic Ocean based 

on genetic sequence analysis (Bano and Hollibaugh, 

2002). The surface mixed layer and the halocline were 

found to harbor distinct bacterial assemblages and, 

despite the relatively small sampling effort (three 

SCICEX cruises), changes in the seasonal distribution 

of some bacterial groups were detected.

The SCICEX program can continue to contribute 

significantly to the growing information on the ocean’s 

microbial diversity (Gross, 2007; DeLong, 2009). 

Current molecular approaches offer a way to analyze 

the detailed ecological dynamics of Arctic microbes 

from samples that can be collected from submarines. 

Properly frozen samples maintain their genomic integrity for years and can continue to be a rich source of 

biological information. For example, the same SCICEX 

samples that were analyzed for bacterial composition 

were used to characterize Archaea populations (Bano 

et al., 2004) and to compare Arctic with Antarctic nitrifying Archaea (Kalenetra et al., 2009). These analyses 

also suggest that there are distinct, environmentally 
24

associated differences within bacterial and archaeal 

groups, and are helping to flesh out the structure of 

polar microbial communities. Importantly, as in other 

ocean regions, most of the bacterial and archaeal 

groups recorded were uncultured forms and many 

of the Arctic groups were distinct from previously 

recorded prokaryotes in lower latitudes. Thus, data 

from future SAMs can continue to contribute to the 

understanding of marine biodiversity. 

Microbial growth in Arctic waters is closely associated 

with the turnover of large amounts of organic carbon 

that can be produced locally or can be derived from 

rivers (Wheeler et al., 1996). Arctic shelves are another 

source of organic carbon to the halocline layer of the 

deeper basin (Bates et al., 2005). Understanding the 

biogeochemical role of the Arctic in global carbon 

cycling, therefore, requires more information on the 

activities of its microbial communities that, despite the 

cold temperatures, can maintain rapid rates of organic 

matter degradation (Rich et al., 1997; Kirchman et al., 

2005). Although information on microbial community composition continues to accumulate (Lovejoy 

et al., 2006), synoptic spatial and seasonal data are not 

presently available. Better seasonal data on microbial 

community associations could aid significantly in 

biogeochemical analyses of the Arctic. Measurements 

of microbial composition and oxygen levels in both 

the surface layer and the upper halocline have high 

biological importance. For example, the abundance 

of groups such as the Cytophaga-like bacteria and the 

Gammaproteobacteria may reflect particulate production in the overlying waters (Elifantz et al., 2007). 

SCICEX measurements of dissolved organic matter 

(DOM) demonstrate the utility of autonomous instrumentation (Guay et al., 1999). The submarine sampling depths include the upper halocline and surface 

waters where large stocks of DOM have been recorded 

(Guéguen et al., 2005).

Currently, one of the most far-reaching biological 

issues in the Arctic is the response of phytoplankton 

production to the reduced summer ice cover extent, 

which has decreased by ~2.5 million square kilometers 

in comparison to the average from the late twentieth 

century. The input of organic matter from ice-edge 

and open-water production impacts both ecological 

dynamics and biogeochemical fluxes of the Arctic. 

Although the ultimate impact of the rapid increase 

in open-water regions for phytoplankton growth 

remains unclear, the response is already significant. 

For instance, the longer open-water season appears 

to be the main factor responsible for increased phytoplankton levels adjacent to the Laptev and East 

Siberian shelves and the Canada Basin (Pabi et al., 

2008). Current nutrient levels in the surface waters 

of most of the Arctic are believed to be insufficient 

to support greatly increased productivity. However, 

nutrient levels could change if mixing and circulation 

patterns are altered in association with changing ice 

conditions. These issues are closely integrated with 

those of the physical response of the Arctic, including 

potential changes in the eddy field of the Arctic Basin, 

which could have significant impacts on its production patterns. Another critical biological issue in the 

Arctic Ocean is the response of its plankton communities to acidification. Calcareous forms such as coccolithophores and pteropods are particularly susceptible 

to lower pH (Doney et al., 2009; Orr et al., 2005, 2009). 

This issue relates directly to objectives already outlined 

in the ocean chemistry section.

SCICEX sampling has included underway sensors for 

chlorophyll a and oxygen that provide information 

on phytoplankton biomass and net community production. Current optically based sensors for oxygen 

collect data much faster than the initial versions and 

are resistant to damage by ice crystals, as compared to 

the Clark-type membrane sensors. Such sensors are 

useful for measurements of photosynthetic production and respiration in the surface layer and deeper 

depths. A variety of in situ methods exist to measure 

phytoplankton biomass and production by fluorescence and other optical approaches. In situ measurements of bulk fluorescence are sensitive but fairly crude 

due to the impact of non-photochemical quenching. 

These problems are significantly less in the nextgeneration instruments, which correct for such effects 
25

using parallel measurements of variable fluorescence 

(Chekalyuk and Hafez, 2008). Variable fluorescence 

also provides an index of photosynthetic capacity to 

enhance the information from the biomass measurement alone. These and additional in situ sensors of 

phytoplankton populations and growth should soon be 

commercially available. 

Sampling Recommendations

The major objective of the recommended SCICEX 

biology sampling program is to document the response 

of Arctic biology to changes in ice cover and other 

climate-induced variability. To this end, we suggest the 

following priority order regarding sampling: 

1. Document the response of Arctic Ocean productivity to reduced sea ice cover.

2. Quantify the interaction between biological processes and changes in the nutrient and carbon 

systems, including the impact of ocean acidification. 

3. Characterize the microbial populations across the 

Arctic Ocean.

4. Record the time-space variation in megafauna 

distributions.

Methods and Implementation

The newly ice-free regions of the Arctic Ocean in 

summer can be sampled along several of the possible 

SCICEX transects, including the Canada Basin and 

Chukchi Plateau (aka Chukchi Borderlands; corridor 1) 

and the Makarov Basin (corridor 2). The orthogonal 

corridors 4 and 5 are of particular interest because they 

traverse a broad region of deep water adjacent to the 

East Siberian and Laptev seas, which have been the 

regions of some of the most dramatic increases in open 

water during summer. The optimal months for tracking the response of primary productivity to changing 

Arctic conditions are spring (May–June just before 

ice retreat) and summer (July–September during 

the expected minimum ice extent). Spring sampling 

provides information on the end-of-winter nutrient 

levels that control the subsequent amount of surface 

productivity, and summer data reflect the actual extent 

of biological production. Nutrient samples can be 

collected jointly with the ocean chemistry component 

and production can be mapped using data from in situ 

fluorescence sensors.

Periodic vertical sampling from the surface layer 

(<100 m) is a high priority. It permits the nutrient and 

biomass levels from the depth of transit (~125 m) to be 

extrapolated to surface conditions. This type of vertical sampling is similar to that outlined in the ocean 

chemistry section and, in most cases, the same vertical 

profile will serve both disciplines. Discrete biological 

samples are needed for phytoplankton identification 

and enumeration, and molecular methods. On-board 

filtration is needed for the molecular samples as well 

as for the chlorophyll a samples to calibrate the external fluorometer. The samples must be frozen and 

otherwise handled as outlined in Table 2. In the past, 

sampling during a vertical excursion of the submarine 

has proved satisfactory for this purpose and requires 

approximately 40 minutes. Several sampling profiles 

should be included in each crossing. Optimal locations are in the permanently ice covered and seasonally 

ice-free regions of corridors 1, 3, 4, and 5. Excursions 

around solar noon would be most useful for assessing 

the submarine light field.

Information on the distribution of bacteria, Archaea, 

and the nutrient, oxygen, and carbon systems is a high 

priority during all seasons. Net production can be 

estimated from the seasonal changes in upper-halocline oxygen and nutrient levels. Nutrient data from 

the winter in all areas of the Arctic Ocean are needed. 

Nitrate sensors that could aid in this goal are now commercially available and have been field-tested. Mapping 

the seasonal impact of high-Arctic productivity on the 

nutrient fields would be most valuable in the northern 

Canada Basin and areas adjacent to the Laptev and East 

Siberian shelf regions. This sampling also addresses 

the goal of bacterial and archaeal community structure and distributions.
26

A variety of additional biological measurements while 

in transit are possible using current sensors or experimental methods with varying amounts of technical 

and methodological development. The planned use 

of the SBE-19 package as described in the ocean 

hydrography section is recommended because this 

instrument is able to accommodate a variety of additional bio-chemical sensors. Deploying fluorescence 

and oxygen sensors is a high priority. More-advanced 

sensors capable of recording variable fluorescence, 

phytoplankton community composition, and DOM 

are also recommended. Other useful biological information can be collected on any of the SAM transits 

with little or no modification to transit depth or other 

operations. For example, during daylight hours, the 

submarine remote video system (SRVS) can be used to 

record the distribution and abundance of large invertebrates, fish, and cetaceans. The population of large 

medusae dramatically increased in the Chukchi and 

Beaufort seas in the 1990s (Brodeur et al., 1999) and 

were clearly visible from the SRVS during the SCICEX 

cruises of the 1990s.

Direct measurements of phytoplankton biomass and 

productivity, bacterial levels, oxygen, and nutrients 

in the water just below the ice will require a dedicated effort because these depths are not accessible 

by the submarine. These depths are some of the 

most productive, however, and have been well characterized on shelves (Cota et al., 1996; Bates et al., 

2005). Such measurements may be best coordinated 

with ICEX experiments.

Bathymetry

Background

Despite the existence of detailed bathymetric maps of 

the northern polar region, such as the International 

Bathymetric Chart of the Arctic Ocean (Jakobsson 

et al., 2008), much of the Arctic Basin has never been 

mapped using modern sounding techniques. This lack 

of data limits geological and geophysical investigations 

of the Arctic Basin and, because topography influences 

Arctic Ocean circulation, it also impacts oceanographic 

research. U.S. Navy nuclear-powered submarines 

played a critical role in acquiring bathymetric data 

for the Arctic. In particular, the SCICEX dedicatedscience missions systematically mapped portions of 

several of the major topographic provinces (Gakkel 

Ridge, Lomonosov Ridge, and Chukchi Borderland) 

that have been inaccessible to icebreakers because of 

perennial sea-ice cover (see Edwards and Coakley, 

2003, and references therein). SCICEX bathymetry and 

backscatter data collected in 1998 and 1999 contributed to two important paradigm shifts in understanding the Arctic Basin. First, that thick ice, either in the 

form of ice shelves (Polyak et al., 2001) or deep draft 

icebergs (Kristoffersen et al., 2004) had extended into 

the interior of the Arctic Basin during the Pleistocene, 

eroding shallow regions of the Alaska Margin, Chukchi 

Borderland, and Lomonosov Ridge. Second, Gakkel 

Ridge is volcanically active and may have erupted as 

recently as 1999, despite being the slowest-spreading 

mid-ocean ridge on Earth (Edwards et al., 2001; Müller 

and Jokat, 2001; Tolstoy et al., 2001).

Bathymetry and backscatter data acquired by 

USS Hawkbill during the 1998 and 1999 SCICEX 

missions provided a base map for the 2001 Arctic 

Mid-Ocean Ridge Expedition (AMORE; Michael et al., 

2003; Schlindwein et al., 2005) and the 2007 Arctic 

Gakkel Vents (AGAVE) expedition (Sohn et al., 2008). 

The latter programs confirmed the existence of volcanism and hydrothermal venting (Edmonds et al., 2003; 

Baker et al., 2004; Sohn et al., 2008) on Gakkel Ridge 

and led to distinctly novel models describing ultraslow seafloor spreading (Dick et al., 2003; Snow and 

Edmonds, 2007). In an interesting twist, the AMORE 

data for the axis of Gakkel Ridge also provided a base 

map for the SCICEX data; because GPS navigation 

was used while collecting AMORE data, they provided an important resource for re-navigating SCICEX 

data to minimize positional errors associated with 

USS Hawkbill’s inertial navigation system. Although 

both AMORE and AGAVE increased the total area 
27

of Gakkel Ridge that has been mapped, SCICEX data 

still provide the most comprehensive coverage of this 

spreading center.

SCICEX data for Lomonosov Ridge informed the 

Integrated Ocean Drilling Program’s 2004 Arctic 

Coring Expedition (ACEX), which successfully collected a 400-m-long composite core containing sediments that span the Cenozoic era (0–65 Ma). Among 

ACEX’s reported findings are warm (~24°C) surface 

waters in the Arctic during the Paleocene/Eocene 

Thermal Maximum (PETM), fresh surface water above 

Lomonosov Ridge ~49 Ma, the first occurrence of 

ice-rafted debris in the core ~45 Ma, and the suggestion that the Arctic Ocean’s perennial ice cover has 

existed for at least 14 million years (Backman et al., 

2006; Moran et al., 2006). A year after ACEX, the 

Healy-Oden Trans-Arctic Expedition (HOTRAX) 

became only the second scientific investigation to 

cross the Arctic Basin using surface vessels. HOTRAX 

researchers collected cores and multichannel seismic 

data, primarily along Chukchi Borderland, Mendeleev 

Ridge, and Lomonosov Ridge, to produce a modern, 

basin-wide paleoclimate record (Darby et al., 2009) as 

well as stratigraphic sections (Polyak et al., 2009).

Sampling Recommendations

Bathymetric mapping during a SCICEX SAM will be 

limited to data that will be collected while underway. 

Thus, the priority for this element of the program is 

to investigate regions in the Arctic Basin that remain 

poorly surveyed and difficult to access via surface 

vessels. The primary focus is Alpha Ridge, a broad 

topographic high located in the Canada Basin that 

extends from the Canadian continental margin to the 

Mendeleev Ridge (Figure 1), but bathymetry data for 

any terrain that has not been mapped previously will 

contribute to the expanding Arctic Basin geophysical 

database. Alpha Ridge is identified as a priority because 

it has the least coverage of any Arctic Basin ridge and 

because its origin remains controversial—at various 

points its formation and evolution have been ascribed 

to processes including continental fragmentation 

(Sweeney et al., 1982), mid-ocean ridge volcanism 

(Vogt and Ostenso, 1970), hotspot volcanism (Vogt 

et al., 1982), and island arc volcanism (Herron et al., 

1974). Currently, the prevailing opinion is that Alpha 

Ridge had an oceanic origin (Jackson et al., 1986; 

Weber and Sweeney, 1990), but that it may have been 

modified by a large impact event (Kristoffersen et al., 

2009). Resolving the processes that formed Alpha 

Ridge is not merely an academic question; claims 

that the Alpha and Mendeleev ridges may be geologically linked have political and economic relevance, especially with sea ice cover diminishing, and 

increasing demand for oil, gas, and minerals, which 

exist in the Arctic.

The nature of future SCICEX SAMs does not allow for 

the systemic “lawn-mowing” types of seafloor surveys 

that were accomplished during the dedicated science 

SCICEX missions. Most SAMs will collect a single 

profile of bathymetric soundings along a transit from 

one side of the Arctic Ocean to the other, or to an ice 

camp and back again. Therefore, the recommended 

strategy is to establish a survey plan that crosses major 

topographic features, including Alpha, Mendeleev, 

Lomonosov, and Gakkel ridges in non-overlapping 

corridors, with emphasis on areas that have not been 

mapped previously. Bathymetric soundings will be 

collected continuously along these tracklines using 

the submarine’s own single-beam echosounder except 

in cases when collection of these data would interfere 

with other science measurements. All three of the long, 

Atlantic-to-Pacific corridors (1, 2, and 3 in Figure 4) 

cross Gakkel and Lomonosov ridges as well as either 

Alpha or Mendeleev Ridge. Corridors 1 and 3 in 

particular cross portions of topographic ridges in the 

Arctic Basin that have very few soundings associated 

with them. Corridor 4 extends from the easternmost 

part of Gakkel Ridge across the portion of Lomonosov 

Ridge attached to Greenland; neither was mapped 

during previous SCICEX missions nor the icebreaker 

expeditions that followed. Corridor 5 runs almost 

perpendicular to Mendeleev Ridge and data collected along this path will extend existing coverage in 

the third dimension. 
28

Methods and Implementation

SCICEX SAMs will benefit from the best available 

navigation data that the Navy can provide to the science community. At present, it is anticipated that a 

ring-laser gyro navigation (RLGN) system will provide inertial navigation for each bathymetry track. 

Typically, the submarine’s RLGN is synched to locations provided by GPS satellites when the submarine 

surfaces. Experience with previous SCICEX data sets, 

which included navigation acquired by the submarine’s 

inertial navigation system, has shown that the locations 

provided by inertial systems while underway can drift 

with time. Thus, it seems prudent, given constraints of 

systems and available time, for the science community 

to assume that the submarines will not be able to cross 

any of the major topographic features at a specific location and instead plan for more general sites within a 

given survey track. Whenever possible, the expectation 

is that, in addition to bathymetric soundings and submarine location, platform attitude and relevant metadata will be released upon completion of the SAMs.
29

The primary objective of the SCICEX Science Plan, Part 1, is to provide the 

Navy’s Arctic Submarine Laboratory with guidance in planning SCICEX Science 

Accommodation Missions. In contrast to the SCICEX cruises that were dedicated 

to the collection of scientific data, the objective of a SAM is to collect unclassified 

data during an otherwise classified submarine exercise. By its nature, the time 

available to plan for a SAM is severely limited. Further, the scientific sampling 

requested during a SAM must dovetail with the planned mission objectives, 

including location, time of year, and submarine class selected for the mission.

The sampling recommendations provided in this element of the SCICEX Science 

Plan are intended to maximize the opportunities to collect scientific data, taking 

advantage of the unique capabilities of the submarine platform. This objective 

is achieved by laying out a wide range of options. The common foundation for 

these options is a set of recommended sampling corridors. Within these sampling 

corridors, priorities are set for ice; ocean hydrography, chemistry, and biology; 

and bathymetry measurements. The individual topical priorities are based on the 

current state of knowledge, derived from observations and models. Each topical 

area assumes that all of the time available during the SAM will be used to make 

measurements of interest to that area. No effort has been made to resolve apparently conflicting recommendations. Rather, it will be the critical responsibility of 

ASL to consider the full range of recommendations in negotiating a SAM with 

the operational Navy. ASL, with intimate knowledge of the planned mission, will 

develop a specific SAM, taking into account and balancing the various priorities, the constraints of the submarine selected for the planned mission, the past 

sampling history, time of the cruise, and other parameters. ASL will also consider 

complementary sampling activities taking place during the ice camps established 

to support ICEX and as part of the Arctic Observing Network, to maximize the 

SCICEX contribution to this integrated network.

Summary
30

In spite of the independent development of the priorities, there are some 

common and distinct points:

a. The routine collection of SCICEX data during direct submarine transits 

between the Atlantic and Pacific oceans and in support of ice camp exercises 

is strongly encouraged, as past and recent experience has shown the value of 

virtually all of the historic submarine-based data.

b. Sampling corridor 1, which runs roughly parallel to 150°W and includes both 

the Recent SCICEX and North Pole tracks, is a high priority on a once-per-year 

basis for all topical areas. 

c. Sampling corridors 2, 4, and 5 are most effectively reached during a SAM 

designed in conjunction with a direct crossing between the Atlantic and 

Pacific oceans.

d. Sampling corridor 3 is most effectively reached during a SAM designed in 

conjunction with an ICEX.

Details regarding the management, quality control, and availability of data collected via a SCICEX SAM remain to be worked out by the SCICEX SAC. This 

guidance will be provided in a separate, companion document. The expectation 

is that all data collected during a SCICEX SAM will be accessible via the National 

Snow and Ice Data Center, in accordance with the SCICEX Phase II MOA.

A key element in the success of the SCICEX SAMs will be their periodic review 

by the SCICEX Science Advisory Committee, specifically, reviewing the utility of 

the Planning Matrix (Appendix A) that forms the centerpiece of the science plan. 

It is expected that modifications will be made to the SCICEX Science Plan as a 

result of these reviews, taking into consideration new sampling technologies and 

insights of the dynamic Arctic Ocean.
31

Anderson, L.G., and S. Kaltin. 2001. Carbon fluxes in the Arctic 

Ocean—potential impact by climate change. Polar Research

20:225–232.

Backman, J., K. Moran, D.B. McInroy, L.A. Mayer, and the 

Expedition 302 Scientists. 2006. Pp. 1–22 in Proceedings of 

the Integrated Ocean Drilling Program. J. Backman, K. Moran, 

D.B. McInroy, L.A. Mayer, and Expedition 302 Scientists, eds., 

Integrated Ocean Drilling Program Management International, 

Inc, Edinburgh, doi:10.2204/iodp.proc.302.2006.

Baker, E.T., H.N. Edmonds, P.J. Michael, W. Bach, H.J.B. Dick, 

J.E. Snow, S.L. Walker, N.R. Banerjee, and C.H. Langmuir. 

2004. Hydrothermal venting in magma deserts: The ultraslowspreading Gakkel and Southwest Indian Ridges. Geochemistry, 

Geophysics, Geosystems 5, Q08002, doi:10.1029/2004GC000712.

Bano, N., and J.T. Hollibaugh. 2002. Phylogenetic composition of 

bacterioplankton assemblages from the Arctic Ocean. Applied 

Environmental Microbiology 68:505–518.

Bano, N., S. Ruffin, B. Ransom, and J.T. Hollibaugh. 2004. 

Phylogenetic composition of Arctic Ocean archaeal assemblages and comparison with Antarctic assemblages. Applied 

Environmental Microbiology 70:781–789.

Bates, N.R., D.A. Hansell, S.B. Moran, and L.A. Codispoti. 2005. 

Seasonal and spatial distribution of particulate organic matter 

(POM) in the Chukchi and Beaufort seas. Deep Sea Research 

Part II 52(24–26):3,324–3,343.

Bluhm, B.A., and R. Gradinger. 2008. Regional variability in food 

availability for arctic marine mammals. Ecological Applications

18(2):S77–S96.

Bourke, R.H., and A.S. McLaren. 1992. Contour mapping of Arctic 

Basin ice draft and roughness parameters. Journal of Geophysical 

Research 97(C11):17,715–17,728.

Bourke, R.H., and R.P. Garrett. 1987. Sea ice thickness distribution in the Arctic Ocean. Cold Regions Science and Technology

13:259–280.

Boyd, T.J., M. Steele, R.D. Muench, and J.T. Gunn. 2002. Partial 

recovery of the Arctic Ocean halocline. Geophysical Research 

Letters 29(14), 1657, doi:10.1029/2001GL014047. 

Brodeur, R.D., C.E. Mills, J.E. Overland, G.E. Walters, and 

J.D. Schumacher. 1999. Evidence for a substantial increase in 

gelatinous zooplankton in the Bering Sea, with possible links to 

climate change. Fisheries Oceanography 8(4):296–306.

Chekalyuk, A., and M. Hafez. 2008. Advanced laser fluorometry 

of natural aquatic environments Limnology and Oceanography

Methods 6:591–609.

Cota G.F., L.R. Pomeroy, W.G. Harrison, E.P. Jones, F. Peters, 

W.M. Sheldon, and T.R. Weingartner. 1996. Nutrients, primary production and microbial heterotrophy in the southeastern Chukchi Sea: Arctic summer nutrient depletion and 

heterotrophy. Marine Ecology Progress Series 135:247–258.

Darby, D.A., L. Polyak, and M. Jakobsson. 2009. The 2005 

HOTRAX Expedition to the Arctic Ocean. Global and Planetary 

Change 68:1–4.

DeLong, E.F. 2009. The microbial ocean from genomes to biomes. 

Nature 459(7244):200–206.

Dick, H.J.B., J. Lin, and H. Schouten. 2003. An ultraslow spreading 

class of ocean ridge. Nature 426:405–412.

Doney, S.C. 2006. The dangers of ocean acidification. Scientific 

American 294:58–65.

Doney, S.C., V.J. Fabry, R.A. Feely, and J.A. Kleypas. 2009. Ocean 

acidification: The other CO2 problem. Annual Review of Marine 

Science 1:169–192.

Edmonds, H.N., P.J. Michael, E.T. Baker, D.P. Connelly, J.E. Snow, 

C.H. Langmuir, H.J.B. Dick, R. Mühe, C.R. German, and 

D.W. Graham. 2003. Discovery of abundant hydrothermal venting on the ultraslow-spreading Gakkel Ridge, Arctic Ocean. 

Nature 421:252–256.

Edwards, M.H., G.J. Kurras, M. Tolstoy, D.R. Bohnenstiehl, 

B.J. Coakley, and J.R. Cochran. 2001. Evidence of recent 

volcanic activity on the ultra-slow spreading Gakkel Ridge. 

Nature 409:808–812.

Edwards, M.H., and B.J. Coakley. 2003. SCICEX investigations of 

the Arctic Ocean System. Chemie de Erde 63(4):281–328.

Elifantz, H., A.I. Dittel, M.T. Cottrell, and D.L. Kirchman. 2007. 

Dissolved organic matter assimilation by heterotrophic bacterial groups in the western Arctic Ocean. Aquatic Microbial 

Ecology 50:39–49. 

Falkowski, P.G., T. Fenchel, and E.F. Delong. 2008. The microbial engines that drive Earth’s biogeochemical cycles. 

Science 320(5879):1034–1039.

Giles, K.A., S.W. Laxon, and A.L. Ridout. 2008. Circumpolar 

thinning of Arctic sea ice following the 2007 record ice 

extent minimum. Geophysical Research Letters 35, L22502, 

doi:10.1029/2008GL035710.

Gross, L. 2007 Untapped bounty: Sampling the seas to survey 

microbial biodiversity. PLoS Biol 5(3):e85, doi:10.1371/journal.

pbio.0050085.

References
32

Guay, C.K., G.P. Klinkhammer, K.K. Falkner, R. Benner, P.G. Coble, 

T.E. Whitledge, B. Black, F.J. Bussell, and T.A. Wagner. 1999. 

High-resolution measurements of dissolved organic carbon in 

the Arctic Ocean by in situ fiber-optic spectrometry. Geophysical 

Research Letters 26:1,007–1,010.

Guéguen, C., L. Guo, and N. Tanaka. 2005. Distributions and characteristics of colored dissolved organic matter in the western 

Arctic Ocean. Continental Shelf Research 25(10):1,195–1,207.

Gunn, J.T., and R.D. Muench. 2001. Observed changes in Arctic 

Ocean temperature structure over the past half decade. 

Geophysical Research Letters 28:1,035–1,038.

Herron, E.M., J.F. Dewey, and W.P. Pitman. 1974. Plate tectonic 

model for the evolution of the Arctic. Geology 4:377–380.

Hester, K.C., E.T. Pelzer, W.J. Kirkwood, and P.G. Brewer. 

2008. Unanticipated consequences of ocean acidification: 

A noisier ocean at lower pH. Geophysical Research Letters 35, 

doi:10.1029/2008GL034913.

Hutchings, J., C. Geiger, A. Roberts, J. Richter-Menge, M. Doble, 

R. Forsberg, K. Giles, C. Haas, S. Hendricks, C. Khambhamettu, 

and others. 2008. Role of ice dynamics in the sea ice mass balance. Eos, Transactions, American Geophysical Union 89(50):515, 

doi:10.1029/2008EO500003.

Interagency Arctic Research Policy Committee (IARPC). 2007. 

Arctic Observing Network: Toward a US Contribution to PanArctic Observing. Arctic Research of the United States, vol. 21. 

Available online at: http://www.nsf.gov/pubs/2008/nsf0842/

index.jsp (accessed May 10, 2010).

Jackson, H.R., D.A. Forsyth, and G.L. Johnson. 1986. Oceanic 

affinities of the Alpha Ridge, Arctic Ocean. Marine 

Geology 73:237–261.

Jakobsson, M., R. Macnab, L. Mayer, R. Anderson, M. Edwards, 

J. Hatzky, H.W. Schenke, and P. Johnson. 2008. An improved 

bathymetric portrayal of the Arctic Ocean: Implications for 

ocean modeling and geological, geophysical and oceanographic analyses. Geophysical Research Letters 35, L07602, 

doi:10.1029/2008GL033520.

Kadko, D., and K. Aagaard. 2009. Glimpses of Arctic Ocean shelfbasin interaction from submarine-borne radium sampling. Deep 

Sea Research Part I 56:32–40.

Kalanetra, K.M., N. Bano, and J.T. Hollibaugh. 2009. Ammoniaoxidizing Archaea in the Arctic Ocean and Antarctic coastal 

waters. Environmental Microbiology 11(9):2,434–2,445, 

doi:10.1111/j.1462-2920.2009.01974.x.

Karcher, M.L., R. Gerdes, F. Kauker, and C. Koeberle. 2003. Arctic 

warming: Evolution and spreading of the 1990s warm event in 

the Nordic Sea and the Arctic Ocean. Journal of Geophysical 

Research 108(C2), 3034, doi:10.1029/2001JC001265.

Kikuchi, T., K. Hatakeyama, and J.H. Morison. 2004. Distribution 

of convective lower halocline water in the eastern Arctic 

Ocean. Journal of Geophysical Research 109, C12030, 

doi:10.1029/20003JC002223.

Kikuchi, T., J. Inoue, and J.H. Morison. 2005. Temperature difference across the Lomonosov Ridge: Implications for the Atlantic 

Water circulation in the Arctic Ocean. Geophysical Research 

Letters 32, L20604, doi:10.1029/2005GL023982.

Kirchman, D.L., R.R. Malmstrom, and M.T. Cottrell. 2005. 

Control of bacterial growth by temperature and organic 

matter in the Western Arctic. Deep Sea Research Part II

52(24–26):3,386–3,395.

Kristoffersen, Y., B. Coakley, W. Jokat, M. Edwards, H. Brekke, 

and J. Gjengedal. 2004. Seabed erosion on the Lomonosov 

Ridge, central Arctic Ocean: A tale of deep draft icebergs 

in the Eurasia Basin and the influence of Atlantic water 

inflow on iceberg motion? Paleoceanography 19, PA3006, 

doi:10.1029/2003PA000985.

Kristoffersen, Y., J.K. Hall, K. Hunkins, J. Ardai, B.J. Coakley, 

J.R. Hopper, and the Healy 2005 Seismic Team. 2009. Extensive 

local seabed disturbance, erosion and mass wasting on Alpha 

Ridge, Central Arctic Ocean: Possible evidence for an extraterrestrial impact? Norwegian Journal of Geology 88:313–320. 

Kwok, R., G.F. Cunningham, H.J. Zwally, and D. Yi. 2007. Ice, 

Cloud, and land Elevation Satellite (ICESat) over Arctic sea 

ice: Retrieval of freeboard. Journal of Geophysical Research 112, 

C12013, doi:10.1029/2006JC003978.

Kwok, R., G.F. Cunningham, M. Wensnahan, I. Rigor, H.J. Zwally, 

and D. Yi. 2009. Thinning and volume loss of the Arctic Ocean 

sea ice cover: 2003–2008. Journal of Geophysical Research 114, 

C07005, doi:10.1029/2009JC005312.

Kwok, R., and D.A. Rothrock. 2009. Decline in Arctic sea ice 

thickness from submarine and ICESat records: 1958–2008. 

Geophysical Research Letters 36, L15501, doi:10.1029/ 

2009GL039035.

Lindsay, R.W., J. Zhang, A.J. Schweiger, M.A. Steele, and H. Stern. 

2009. Arctic sea ice retreat in 2007 follows thinning trend. 

Journal of Climate 22:165–176, doi:10.1175/2008JCLI2521.1. 

Lovejoy, C., R. Massana, and C. Pedrós-Alió. 2006. Diversity and 

distribution of marine microbial eukaryotes in the Arctic Ocean 

and adjacent seas. Applied and Environmental Microbiology

72(5):3,085–3,095

Macdonald, R.W., E.C. Carmack, F.A. McLaughlin, K.K. Falkner, 

and J.H. Swift. 1996. Connections among ice, runoff, and 

atmospheric forcing in the Beaufort Gyre. Geophysical Research 

Letters 26:2,223–2,226.

Maslowski, W., J.L. Clement, and J. Jakacki. 2007. Toward prediction of environmental Arctic change. Computing in Science and 

Engineering 9:29–34.

McLaren, A.S., R.G. Barry, and R.H. Bourke. 1990. Could Arctic ice 

be thinning? Nature 345:762.

McLaughlin, F.A., E.C. Carmack, R.W. Macdonald, and J.K. Bishop. 

1996. Physical and geochemical properties across the Atlantic/

Pacific water mass front in the southern Canadian Basin. Journal 

of Geophysical Research 101:1,183–1,197.
33

Melling H., D.A. Riedel, and Z. Gedalof. 2005. Trends in 

the draft and extent of seasonal pack ice, Canadian 

Beaufort Sea. Geophysical Research Letters 32, L24501, 

doi:10.1029/2005GL024483.

Michael, P.J., C.H. Langmuir, H.J.B. Dick, J.E. Snow, S.L. Goldstein, 

D.W. Graham, K. Lehnert, G. Kurras, W. Jokat, R. Mühe, and 

H.N. Edmonds. 2003. Magmatic and amagmatic seafloor generation at the ultraslow-spreading Gakkel Ridge, Arctic Ocean. 

Nature 423:956–961.

Mizuno, K., and T. Watanabe. 1998. Preliminary results of insitu CTD/CTD comparison test. Journal of Oceanography

54:373–380.

Moran, K., J. Backman, H. Brinkhuis, S.C. Clemens, T. Cronin, 

G.R. Dickens, F. Eynaud, J. Gattacceca, M. Jakobsson, 

R.W. Jordan, and others. 2006. The Cenozoic palaeoenvironment 

of the Arctic Ocean. Nature 441:601–605.

Morison, J., M. Steele, and R. Andersen. 1998. Hydrography of 

the upper Arctic Ocean measured from the nuclear submarine 

U.S.S. Pargo. Deep-Sea Research I 45(357):15–38.

Muench, R.D., J.T. Gunn, T.E. Whitledge, P. Schlosser, and 

W. Smethie. 2000. An Arctic Ocean cold core eddy. Journal of 

Geophysical Research 105:23,997–24,006.

Müller, C., and W. Jokat. 2000. Seismic evidence for volcanic activity discovered in central Arctic. Eos, Transactions, American 

Geophysical Union 81:265–269.

Nghiem, S.V., I.G. Rigor, D.K. Perovich, P. Clemente-Colon, 

J.W. Weatherly, and G. Neumann. 2007. Rapid reduction of 

Arctic perennial sea ice. Geophysical Research Letters 34, L19504, 

doi:10.1029/2007GL031138. 

Orr, J.C., V.J. Fabry, O. Aumont, L. Bopp, S.C. Doney, R.A. Feely, 

A. Gnanadesikan, N. Gruber, A. Ishida, F. Joos, and others. 2005. 

Anthropogenic ocean acidification over the twenty-first century 

and its impact on calcifying organisms. Nature 437:681–686.

Orr, J.C., K. Caldeira, V.J. Fabry, J.-P. Gattuso, P. Haugan, 

P. Lehodey, S. Pantoja, H.-O. Portner, U. Riebesell, T. Trull, 

and others. 2009. Research priorities for ocean acidification. 

Report presented for the Second Symposium on the Ocean 

in a High-CO2 World, Monaco, October 6–9, convened by 

SCOR, IOC-UNESCO, IAEA, and IGBP, 23 pp. Available 

online at: http://www.ocean-acidification.net/Symposium2008/

ResearchPrioritiesReport_OceanHighCO2WorldII.pdf (accessed 

May 11, 2010).

Pabi, S., G.L. van Dijken, and K.R. Arrigo. 2008. Primary production in the Arctic Ocean, 1998–2006. Journal of Geophysical 

Research 113, C08005, doi:10.1029/2007JC004578.

Pfirman, S., W.F. Haxby, R. Colony, and I. Rigor. 2004. Variability 

in Arctic sea ice drift. Geophysical Research Letters 31, L16402, 

doi:10:1029/2004GL020063.

Polyak, L., J. Bischof, J.D. Ortiz, D.A. Darby, J.E.T. Channell, 

C. Xuan, D.S. Kaufman, R. Løvlie, D. Schneider, R. Adler, and 

E. Council. 2009. Late Quaternary stratigraphy and sedimentation patterns in the western Arctic Ocean. Global and Planetary 

Change 68:5–17.

Polyak, L., M.H. Edwards, B.J. Coakley, and M. Jakobsson. 2001. 

Existence of Arctic ice shelves during the Pleistocene inferred 

from deep-sea glaciogenic bedforms. Nature 410:453–457.

Polyakov, I.V., G.V. Aleekseev, L.A. Timokhov, V.S. Bhatt, 

R.L. Colony, H.L. Simmons, D. Walsh, J.E. Walsh, and 

V.F. Zakharov. 2004. Variability of Intermediate Atlantic 

Water of the Arctic Ocean over the last 100 years. Journal of 

Climate 17:4,485–4,496.

Rich J., M. Gosselin, E. Sherr, B. Sherr, and D.L. Kirchman. 1997. 

High bacterial production, uptake and concentrations of dissolved organic matter in the central Arctic Ocean. Deep-Sea 

Research Part II 44(8):1,645–1,663. 

Richter-Menge, J.A., D.K. Perovich, B.C. Elder, K. Claffey, I. Rigor, 

and M. Ortmeyer. 2006. Ice mass balance buoys: A tool for measuring and attributing changes in the thickness of the Arctic sea 

ice cover. Annals of Glaciology 44:205–210.

Richter-Menge, J., J. Overland, M. Svoboda, J. Box, M.J.J.E. Loonen, 

A. Proshutinsky, V. Romanovsky, D. Russell, C.D. Sawatzk, 

M. Simpkins, and others. 2008. Arctic Report Card 2008. http://

www.arctic.noaa.gov/reportcard.

Rigor, I., and J.M. Wallace. 2004. Variations in the age of Arctic seaice and summer sea-ice extent. Geophysical Research Letters 31, 

L09401, doi:10.1029/2004GL019492.

Rothrock, D., W. Maslowski, D. Chayes, G. Flato, J. Grebmeier, 

R. Jackson, R. Sambrotto, W. Smethie, W. Sternberger, J. Swift, 

J. Tarduno, and A. Thorndike. 1999a. Arctic Ocean Science from 

Submarines: A Report Based on the SCICEX 2000 Workshop. 

Applied Physics Laboratory, University of Washington, Seattle, 

WA, 27 pp with 7 appendices.

Rothrock, D.A., and M. Wensnahan. 2007. The accuracy of 

sea-ice drafts measured from U.S. Navy submarines. Journal 

of Atmospheric and Oceanic Technology 24:1,936-1,949, 

doi:10.1175/JTECH2097.1.

Rothrock, D.A., and J. Zhang. 2005. Arctic Ocean sea ice volume: 

What explains its recent depletion? Journal of Geophysical 

Research 110, C01002, doi:10.1029/2004JC002282.

Rothrock, D.A., D.B. Percival, and M. Wensnahan. 2008. The 

decline in arctic sea-ice thickness: separating the spatial, 

annual, and interannual variability in a quarter century of 

submarine data. Journal of Geophysical Research 113, C05003, 

doi:1029/2007JC004252.

Rothrock, D.A., Y. Yu, and G.A. Maykut. 1999b. Thinning of the 

Arctic sea-ice cover. Geophysical Research Letters 26:3,469–3,472.

Schlindwein, V., C. Müller, and W. Jokat. 2005. Seismoacoustic 

evidence for volcanic activity on the ultraslow-spreading Gakkel 

Ridge, Arctic Ocean. Geophysical Research Letters 32, L18306, 

doi:10.1029/2005GL023767.

Shimada, K., F. McLaughlin, E. Carmack, A. Proshutinsky, 

S. Nishino, and M. Itoh. 2004. Penetration of the 1990s 

warm temperature anomaly of Atlantic Water in the 

Canada Basin. Geophysical Research Letters 31, L20301, 

doi:10.1029/2004GL020860. 
34

Shimada, K., T. Kamoshida, M. Itoh, S. Nishino, E. Carmack, 

F. McLaughlin, S. Zimmermann, and A. Proshutinsky. 2006. 

Pacific Ocean inflow: Influence on catastrophic reduction of sea 

ice cover in the Arctic Ocean. Geophysical Research Letters 33, 

L08605, doi:10.1029/2005GL025624.

Shy, T.L., and J.E. Walsh. 1996. North Pole ice thickness and association with ice motion history 1977–1992. Geophysical Research 

Letters 23(21):2,975–2,978, doi:10.1029/96GL02823.

Smetacek, V., and S. Nicol. 2005. Polar ocean ecosystems in a 

changing world. Nature, 437(7057):362.

Smethie, W.M., P. Schlosser, G. Bonisch, and T.S. Hopkins. 2000. 

Renewal and circulation of intermediate waters in the Canadian 

Basin observed on the SCICEX 96 cruise. Journal of Geophysical 

Research 105:1,105–1,121. 

Smith, J.N., K.M. Ellis, and T. Boyd. 1999. Circulation features in 

the central Arctic Ocean revealed by nuclear fuel reprocessing 

tracers from Scientific Ice Expeditions 1995 and 1996. Journal of 

Geophysical Research 104:29,663–29,677.

Snow, J.E., and H.N. Edmonds. 2007. Ultraslow-spreading ridges: 

rapid paradigm changes. Oceanography 20(1):90–101.

Sohn, R.A., C. Willis, S. Humphris, T.M. Shank, H. Singh, 

H.N. Edmonds, C. Kunz, U. Hedman, E. Helmke, M. Jakuba, 

and others. 2008. Explosive volcanism on the ultraslow-spreading Gakkel ridge, Arctic Ocean. Nature 453:1,236–1,238.

Steele, M., and T. Boyd. 1998. Retreat of the cold halocline layer in the Arctic Ocean. Journal of Geophysical 

Research 103:10,491–10,435.

Steele, M., J. Morison, W. Ermold, I. Rigor, and M. Ortmeyer. 

2004. Circulation of summer Pacific halocline water in the 

Arctic Ocean. Journal of Geophysical Research 109, C02027, 

doi:10.1029/2003JC002009.

Steinacher, M., F. Joos, T.L. Forlicher, G.-K. Plattner, and 

S.C. Doney. 2008. Imminent ocean acidification projected 

with the NAR global coupled carbon cycle-climate model. 

Biogeosciences Discussions 5:4,353–4,393.

Sweeney, J.F., J.R. Weber, and S.M. Glasco. 1982. Continental 

ridges in the Arctic Ocean: LORAX constraints. Tectonophysics

89:217–237.

Swift, J.H., E.P. Jones, K. Aagaard, E.C. Carmack, M. Hingston, 

R.W. Macdonald, F.A. McLaughlin, and R.G. Perkin. 1997. 

Waters of the Makarov and Canada basins. Deep-Sea Research 

Part II 44:1,503–1,529.

Tanhua, T., E.P. Jones, E. Jeansson, S. Jutterstrom, W.M. Smethie, Jr., 

D.W.R. Wallace, and L.G. Anderson. 2009. Ventilation of the 

Arctic Ocean: Mean ages and inventories of anthropogenic 

CO2 and CFC-11. Journal of Geophysical Research 114, C01002, 

doi:10.1029/2008JC004868.

Tolstoy, M., D.R. Bohnenstiehl, M.H. Edwards, and G.J. Kurras. 

2001. Seismic character of volcanic activity at the ultraslowspreading Gakkel Ridge. Geology 29:1,139–1,142.

Tucker, W.B., J.W. Weatherly, D.T. Eppler, L.D. Farmer and 

D.L. Bentley. 2001. Evidence for rapid thinning of sea ice in 

the western Arctic Ocean at the end of the 1980s. Geophysical 

Research Letters 28:2,851–2,854.

Vogt, P.R., and N. Ostenso. 1970. Magnetic and gravity 

profiles across the Alpha Cordillera and their relationship to Arctic seafloor spreading. Journal of Geophysical 

Research 75:4,925–4,937.

Vogt, P.R., P.T. Taylor, L.C. Kovacs, and G.L. Johnson. 1982. The 

Canada Basin: Aeromagnetic constraints on structure and evolution. Tectonophysics 89:295–336.

Wadhams, P. 1990. Evidence for thinning of the Arctic ice cover 

north of Greenland. Nature 345:795–797.

Wadhams, P., and N.R. Davis. 2000. Further evidence of 

ice thinning in the Arctic Ocean. Geophysical Research 

Letters 27(24):3973–3975.

Weber, J.R., and J.F. Sweeney. 1990. Ridges and basin in the central 

Arctic Ocean. Pp. 305-336 in The Arctic Ocean Region, vol. L. 

A. Grantz, G.L. Johnson, and J.F. Sweeney, eds., Geological 

Society of America, Boulder, CO.

Wensnahan, M., and D.A. Rothrock. 2005. Sea-ice draft from 

submarine-based sonar: Establishing a consistent record 

from analog and digitally recorded data. Geophysical Research 

Letters 32, L11502, doi:10:1029/2005GL022507.

Wensnahan, M., D.A. Rothrock, and P. Hezel. 2007. New Arctic 

sea ice draft data from submarines. Eos, Transactions, American 

Geophysical Union 88(5):55–56.

Wheeler P.A., M. Gosselin, E. Sherr, D. Thibault, D.L. Kirchman, 

R. Benner, and T.E. Whitledge. 1996. Active recycling of organic 

carbon in the central Arctic Ocean. Nature 380:697–699.

Wheeler, P.A., J.M. Watkins, and R.L. Hansing. 1997. Nutrients, 

organic carbon, and organic nitrogen in the upper water column 

of the Arctic Ocean: Implications for sources of dissolved 

organic carbon. Deep-Sea Research Part II 44:1,571–1,592.

Woodgate, R.A., K. Aagaard, J.H. Swift, W.M. Smethie Jr., 

and K.K. Falkner. 2007. Atlantic water circulation over the 

Mendeleyev Ridge and Chukchi Borderland from thermohaline 

intrusions and water mass properties. Journal of Geophysical 

Research 112, C02005, doi:10.1029/2005JC003416.

Yu, Y., G.A. Maykut, and D.A. Rothrock. 2004. Changes in the 

thickness distribution of Arctic sea ice between 1958–1970 

and 1993–1997. Journal of Geophysical Research 109, C0004, 

doi:10.1029/2003JC001982.

Zhang, J., and M. Steele. 2007. Effect of vertical mixing on the 

Atlantic Water layer circulation in the Arctic Ocean. Journal of 

Geophysical Research 112, C04S04, doi:10.1029/2006JC003732. 
35

 Appendix A

Planning Matrix

General Remarks

•	 For safe operation, submarines will travel more slowly at shallower

depths; typical past SCICEX operating speeds have been around 14 kts 

at keel depth of 134 m (440 ft) and 16 kts at keel depth of 229 m (750 ft)

Terminology

•	 Ice draft sampling: Spacing between segments is the distance from the

end of one segment to the beginning of the next

•	 Ocean chemistry sampling: Transient tracers include tritium, 3

He, SF6 , 

129 I, and CFCs; the vertical suite includes salinity, nutrients (frozen), 

oxygen, 18O, and transient tracers 

Sampling Requests

Ice Draft

•	 Prefer sampling in April–May and September–November

Ocean Hydrography

•	 Prefer sampling in spring or ice minimum thru freeze

•	 Samples collected as deep as possible (keel depth near 244 m [800 ft]),

particularly when passing over (within ±100 km) ridges, to sample 

variability of along-ridge AW flows

•	 When possible, loiter at ice edge to collect a dense sampling array of

water conditions

Ocean Chemistry and Biology

•	 Prefer transit depth of 61 m (200 ft), near the top of the halocline

Ocean Chemistry

•	 Prefer sampling in spring–September with highest priority in September

Ocean Biology

•	 Prefer sampling in spring–September with high priority at ice minimum

in September
36

Table A-1. Atlantic-Pacific Transit: Direct Crossing

Sampling 

Corridor

Time Required (days)

Priority Ship’s Parameters Comments Revisit

Frequency

Transit Science Total 

0 0 0

In general:

If no time 

available to 

deviate to 

higher priority 

track, request 

collection of 

SCICEX data 

along direct 

transit

All: 

1 per year

0 0.5 0.5

0 1 1

0 1.5 1.5
37

Science Priorities

Bathy Ice

Ocean

Hydrography Chemistry Biology

Continuous

Continuous at transit speed 

General approach:

Focus XCTDs from Amundsen 

Basin to Mendeleyev Ridge

(85°N 5°E to 83°N 173°W 

is approx 1300 km)

18O, salinity, 

nutrients (frozen) hourly

Transient tracers every 2 hrs

Chlorophyll fluorescence, 

oxygen, submarine light, and 

nitrate measured continuously

 Particulate material

 frozen every 2 hrs

10 50-km segments

@ 14 kt, 122-m depth:

2 Atlantic side,

2 Pacific side of NP,

6 Pacific side @ 200-km spacing,

Remainder continuous at 

transit speed

18 extra XCTDs

@ 60-km spacing

= 1080 km

= 9.7 deg of lat

18O, salinity, 

nutrients (frozen) hourly

Transient tracers every 2 hrs 

18O, salinity, nutrients (frozen) 

from mixed layer at each 

XCTD station

Underway radium sampling

Vertical sampling suite: 

(Estimated time: 12–18 hrs) 

5–6 depth stairstep extending 

from surface mixed layer 

to 230 m at approximately 

12–16 XCTD stations evenly 

distributed along track

Chlorophyll fluorescence, 

oxygen, submarine light, and 

nitrate measured continuously

Particulate material 

frozen every 2 hrs

Carbon system every 2 hrs

Vertical sampling for discrete 

samples as for chemistry: 

5–6 depth stairstep extending 

from surface mixed layer to 

230 m at XCTD stations

20 50-km segments

@ 14 kt, 122-m depth:

2 Atlantic side NP,

2 Pacific side of NP,

16 Pacific side @ 50-km spacing,

Remainder continuous at 

transit speed

36 extra XCTDs

@ 40-km spacing

= 1440 km

= 12.9 deg of lat

30 50-km segments

@ 14 kt, 122-m depth:

2 Atlantic side of NP,

Remainder continuous 

Pacific side

54 extra XCTDs 

@ 40-km spacing

= 2160 km

= 19.5 deg of lat

(transit is approx 2200 km 

in length) 
38

Table A-2. Atlantic-Pacific Transit: North Pole Track

Sampling 

Corridor

Time Required (days)

Priority Ship’s Parameters Comments Revisit

Frequency

Transit Science Total 

1

2 0 2

Ice: 1

Hydro: 1

Chem: 1

Bio: 2

All:

1 per year for 

either North Pole 

Track or Recent 

SCICEX Track

2 0.5 2.5

2 1 3

2 1.5 3.5

2 2 4
39

Science Priorities

Bathy Ice

Ocean

Hydrography Chemistry Biology

Choose an Alpha Ridge line; Otherwise continuous

Continuous at transit speed 

General approach: 

Deploy XCTDs with finer 

resolution over Lomonosov R, 

coarser resolution over 

Amundsen B and Canadian B 

(track from 85°N 30°E to 

73°N 150°W is approx 2500 km) 

Up to full samples ICW XCTDs

18O and nutrients 

(frozen) hourly

Transient tracers every 2 hrs

Chlorophyll fluorescence, 

oxygen, submarine light, and 

nitrate measured continuously

Particulate material frozen 

every 2 hrs

10 50-km segments

@ 14 kt, 122-m depth:

2 Atlantic side NP,

2 Pacific side NP,

6 Pacific side @ 260-km spacing,

Remainder continuous 

at transit speed

18 extra XCTDs

@ 60-km spacing

= 1080 km

= 9.7 deg of lat

18O, salinity, 

nutrients (frozen) hourly

Transient tracers every 2 hrs 

18O, salinity, nutrients (frozen) 

from mixed layer at each 

XCTD station

 Underway radium sampling

Vertical sampling suite:

(Estimated time: 12–18 hrs)

5–6 depth stairstep extending 

from surface mixed layer 

to 230 m at approximately 

12–16 XCTD stations evenly 

distributed along track

Chlorophyll fluorescence, 

oxygen, submarine light, and 

nitrate measured continuously

Particulate material 

frozen every 2 hrs

Carbon system every 2 hrs

Vertical sampling for discrete 

samples as for chemistry:

5–6 depth stairstep extending 

from surface mixed layer to 

230 m at XCTD stations

Concentrate sampling across 

the ice edge in Aug–Sep 

20 50-km segments

@ 14 kt, 400 ft depth:

 2 Atlantic side NP,

 2 Pacific side of NP,

16 Pacific side @ 70-km spacing,

Remainder continuous

at transit speed

36 extra XCTDs

@ 40-km spacing

= 1440 km

= 12.9 deg of lat

30 50-km segments

@ 14 kt, 122-m depth: 

2 Atlantic side of NP,

2 Pacific side of NP,

26 Pacific side @ 25-km spacing,

Remainder continuous

at transit speed

54 extra XCTDs

@ 40-km spacing

= 2160 km

= 19.5 deg of lat

40 50-km segments

@ 14 kt, 122-m depth:

2 Atlantic side NP,

Continuous Pacific side

72 extra XCTDs

@ 40-km spacing

= 2880 km

= 25.9 deg of lat
40

Table A-3. Atlantic-Pacific Transit: Recent SCICEX Track

Sampling 

Corridor

Time Required (days)

Priority Ship’s Parameters Comments Revisit

Frequency

Transit Science Total 

1

3 0 3

All: 1 Preference to repeat 1998–2003 

transects, if time allows

All:

1 per year for either 

North Pole Track or 

recent SCICEX Track

3 0.5 3.5

3 1 4
41

Science Priorities

Bathy Ice

Ocean

Hydrography Chemistry Biology

Choose an Alpha Ridge line; Otherwise continuous

Continuous at transit speed 

General approach:

Deploy XCTDs with finer 

resolution over Lomonosov R, 

coarser resolution over 

Amundsen B and Canadian B 

(track from 85°N 45°E to 

73°N 156°W is approx 2500 km)

18O, salinity, 

nutrients (frozen) hourly

Transient tracers every 2 hrs Chlorophyll fluorescence, 

oxygen, submarine light, and 

nitrate measured continuously

 Particulate material

 frozen every 2 hrs

 Carbon system every 2 hrs

Vertical sampling for discrete 

samples as for chemistry:

5–6 depth stairstep extending 

from surface mixed layer to 

230 m at XCTD stations

 Concentrate sampling across 

the ice edge in Aug–Sep

10 50-km segments

@ 14 kt, 122-m depth:

4 in region nearest NP,

6 Pacific side @ 260-km spacing,

Remainder continuous

at transit speed

18 extra XCTDs

@ 60-km spacing

= 1080 km

= 9.7 deg of lat

18O, salinity, 

nutrients (frozen) hourly

Transient tracers every 2 hrs

18O, salinity, nutrients (frozen) 

from mixed layer at each 

XCTD station

 Underway radium sampling

Vertical sampling suite:

(Estimated time: 12–18 hours)

5–6 depth stairstep extending 

from surface mixed layer to 

230 m at approximately

 12–16 XCTD stations evenly 

distributed along track

20 50-km segments

@ 14 kt, 122-m depth:

4 in region nearest NP,

16 Pacific side @ 70-km spacing,

Remainder continuous

at transit speed 

36 extra XCTDs

@ 40-km spacing

= 1440 km

= 12.9 deg of lat
42

Table A-4. Atlantic-Pacific Transit: Eastern Offset Track

Sampling 

Corridor

Time Required (days)

Priority Ship’s Parameters Comments Revisit

Frequency

Transit Science Total 

2 & 4

1 0 1

Ice: 2

Hydro: 2

Chem: 2

Bio: 1

Fast outside E-W line

*Ice:

E-W section 

(through North Pole) 

of more interest

Loiter at ice edge 

in summer

Ice: 1 per 2 years

Hydro: 1 per 2 years

Chem: 1 per year 

Bio: 1 per year

1 0.5 1.5

1 1 2

1 1.5 2.5

1 2 3
43

Science Priorities

Bathy Ice

Ocean

Hydrography Chemistry Biology

Continuous

Continuous at transit speed 

General approach:

Focus XCTDs in Makarov 

Basin (corridor 2), then deploy 

additional XCTDs in Amundsen 

Basin (corridor 4)

18O, salinity, 

nutrients (frozen) hourly

Transient tracers every 2 hrs

Chlorophyll fluoresence, 

oxygen, submarine light, and 

nitrate measured continuously

 Genetic material

 frozen every 2 hrs

10 50-km segments 

@ 14 kt, 122-m depth:

10 E-W lines @ 40-km spacing,

Remainder continuous

at transit speed

 18 extra XCTDs

@ 60 km spacing

= 1080 km

(84°N 135°E to 78°N 173°W

 is approx 1100 km along 

corridor 2) 

18O, salinity, 

nutrients (frozen) hourly

Transient every tracers 2 hrs

18O, salinity, nutrients (frozen) 

from mixed layer at each 

XCTD station

 Underway radium sampling

Vertical sampling suite:

(Estimated time: 12–18 hrs)

5–6 depth stairstep extending 

from surface mixed layer to 

230 m at approximately

 12–16 XCTD stations evenly 

distributed along track

Chlorophyll fluorescence, 

oxygen, submarine light, and 

nitrate measured continuously

 Particulate material

 frozen every 2 hrs

 Carbon system every 2 hrs

Vertical sampling for discrete 

samples as for chemistry:

5–6 depth stairstep extending 

from surface mixed layer to 

230 m at XCTD stations

 Concentrate sampling across 

the ice edge in Aug–Sep

20 50-km segments

@ 14 kt, 122-m depth:

20 continuous E-W lines,

Remainder continuous

at transit speed

 36 extra XCTDs

@ 40 km spacing

= 1440 km

 (84°N 120°E to 76°N 165°E

 is approx 1200 km along 

corridor 2) 

30 50-segments

@ 14 kt, 122-m depth:

18 continuous E-W lines,

12 N-S lines @ 100-km spacing,

Remainder continuous 

at transit speed

54 extra XCTDs

@ 40 km spacing

= 2160 km

(NP to 84°N 120°E adds approx 

700 km along corridor 4)

40 50-km segments

@ 14 kt, 122-m depth:

18 continuous E-W lines,

22 N-S lines @ 35-km spacing,

Remainder continuous 

at transit speed

72 extra XCTDs

@ 30-km spacing

= 2160 km

(87°N 60°W to 84°N 120°E 

adds approx 1000 km along 

corridor 4)
44

Table A-5. Atlantic-Pacific Transit: Cross Canada Basin Track

Sampling 

Corridor

Time Required (days)

Priority Ship’s 

Parameters Comments RevisitFrequency

Transit Science Total 

2, 3, & 5

2.5 0 2.5

Ice: 2

Hydro: 3

Chem: 2

Bio: 1

Hydro: 

Prefer sampling along corridor 2, 

assuming sampling along the 

Canadian Margin (corridor 3) is likely 

to take place on ice camp transit

Hydro:

Spring and summer cruises should 

consider coordination with 

Beaufort Gyre experiment (e.g., tend 

to prefer spring cruise, due to 

summer coverage via Beaufort Gyre 

experiment; however, summer 

cruises extend work beyond the 

sunset of BG Exp)

Ice: 1 per 2 years

Hydro: 1 per 2 years

Chem: 1 per 2 years 

Bio: 1 per year

2.5 0.5 3

2.5 1 3.5

2.5 1.5 4
45

Science Priorities

Bathy Ice

Ocean

Hydrography Chemistry Biology

Choose an Alpha Ridge line; Otherwise continuous

Continuous at transit speed 

General approach:

Focus XCTDs in Canada Basin 

(corridor 5), then deploy 

additional XCTDs along 

Canadian margin (corridor 3)

Up to full samples

ICW XCTDs

18O and nutrients 

(frozen) hourly

Transient tracers every 2 hrs

Spring: 1. Cross-track and 

Canadian margin; 

2. E. Siberian margin

Summer/fall: 

1. Ice edge; 2. Cross-track, and 

Canadian margin

Chlorophyl fluorescence, 

oxygen, submarine light, and 

nitrate measured continuously

Genetic material frozen 

every 2 hrs

10 50-km segments

@ 14 kt, 12-m depth: 

1 at NP,

3 Canada Margin @ 300-

km spacing,

6 E-W lines @ 200-km spacing,

Remainder continuous

at transit speed

18 extra XCTDs in Canada Basin

@ 50-km spacing

= 900 km

(81°N 130°W to 81°N 180°W 

is approx 850 km along 

corridor 5)

18O, salinity, 

nutrients (frozen) hourly

Transient tracers every 2 hrs

18O, salinity, nutrients (frozen) 

from mixed layer at each 

XCTD station

 Underway radium sampling

Vertical sampling suite:

(Estimated time: 12–18 hrs)

5–6 depth stairstep extending 

from surface mixed layer 

to 230 m at approximately 

12–16 XCTD stations evenly 

distributed along track

Chlorophyll fluorescence, 

oxygen, submarine light, and 

nitrate measured continuously

 Particulate material

 frozen every 2 hrs

 Carbon system every 2 hrs

Vertical sampling for discrete 

samples as for chemistry:

5–6 depth stairstep extending 

from surface mixed layer to 

230 m at XCTD stations

 Concentrate sampling across 

the ice edge in Aug–Sep on 

Mendelyev side of track

20 50-km segments

@ 14 kt,122-m depth:

1 at NP,

2 northern E-W lines @ 

15- km spacing,

6 Canadian Margin @ 

125-km spacing,

11 E-W lines @ 100-km spacing,

Remainder continuous

at transit speed

36 extra XCTDs in Canada Basin

@ 40-km spacing

= 1440 km

 (81°N 130°W to 80°N 165°E 

is approx 1150 km along 

corridor 5) 

30 50-km segments

@ 14 kt, 122 m depth:

1 at NP,

3 northern E-W lines @ 

50-km spacing,

10 Canadian Margin @ 

50-km spacing,

16 E-W lines @ 50-km spacing,

Remainder continuous

at transit speed

54 extra XCTDs

@ 40-km spacing

= 2160 km

(81°N 130°W to 87°N 60°W 

adds approx 950 km along 

corridor 3)
46

Sampling 

Corridor

Time Required (days)

Priority Ship’s Parameters Comments Revisit

Frequency

Transit Science Total 

0 0 0

In general:

If no time available 

to deviate to 

higher priority 

track, request 

collection of 

SCICEX data along 

direct transit

All:

1 per 2 year

0 0.5 0.5

0 1 1

0 1.5 1.5

Table A-6. Ice-Camp Transit: Direct Atlantic-Pacific Crossing via Ice Camp
47

Science Priorities

Bathy Ice

Ocean

Hydrography Chemistry Biology

Choose an Alpha Ridge line; Otherwise continuous

Continuous at transit speed 

General approach: 

Focus XCTDs first from

 Lomonosov R to Canada B.

(87°N 45°W to 82°N 140°W is 

approx 1200 km)

18O, salinity, nutrients 

(frozen) hourly

Transient tracers 2 hrs 

Chlorophyll fluorescence, 

oxygen, submarine light and 

nitrate measured continuously

10 50-km segments

@ 14 kt, 122-m depth

@ 150-km spacing

Remainder continuous

 at transit speed

18 extra XCTDs

@ 60-km spacing

= 1080 km 18O, salinity, nutrients 

(frozen) hourly

Transient tracers every 2 hrs 

18O, salinity, nutrients (frozen) 

from mixed layer at each 

XCTD station

 Underway radium sampling

Vertical sampling suite:

(Estimated time: 12–18 hrs)

5–6 depth stairstep extending 

from surface mixed layer to 

230 m at approximately

 12–16 XCTD stations evenly 

distributed along track

Chlorophyll fluorescence, 

oxygen, submarine light and 

nitrate measured continuously

 Particulate material

 frozen every 2 hrs

 Carbon system every 2 hrs

Vertical sampling for discrete 

samples as for chemistry:

5–6 depth stairstep extending 

from surface mixed layer to 

230 m at XCTD stations

 Concentrate sampling across 

the ice edge in Jun–Sep

20 50-km segments

@ 14 kt, 122-m depth

 @ 50-km spacing

Remainder continuous 

at transit speed

36 extra XCTDs 

@ 40-km spacing = 1440 km

@ 60-km spacing = 2160 km

30 50-km segments

@ 14 kt, 122-m depth

@ 20-km spacing

Remainder continuous 

at transit speed

54 extra XCTDs

@ 40-km spacing

= 2160 km 

(transit from 87°N 45°W 

to 72°N 145°W is 

approx 2200 km)
48

Table A-7. Ice-Camp Transit: North Pole Track

Sampling 

Corridor

Time Required (days)

Priority Ship’s Parameters Comments Revisit

Frequency

Transit Science Total 

1

0.5 0 0.5

Ice: 1

Hydro: 1

Chem: 1

Bio: 2

All: 

1 per 2 year for either 

North Pole Track or recent 

SCICEX Track

0.5 0.5 1

0.5 1 1.5

0.5 1.5 2

0.5 2 2.5
49

Science Priorities

Bathy Ice

Ocean

Hydrography Chemistry Biology

Choose an Alpha Ridge line; Otherwise continuous

Continuous at transit speed 

General approach:

Deploy XCTDs with finer 

resolution over Lomonosov R,

coarser resolution 

over Amundsen B and 

Canadian B (track from 

85°N 30°E to 72°N 150°W is 

approx 2500 km) 18O, salinity, nutrients 

(frozen) hourly

Transient tracers every 2 hrs

18O, salinity, nutrients (frozen) 

from mixed layer at each 

XCTD station

 Underway radium sampling

Vertical sampling suite: 

(Estimated time: 12–18 hrs)

5–6 depth stairstep extending 

from surface mixed layer to 

230 m at approximately

 12–16 XCTD stations evenly 

distributed along track

Chlorophyll fluorescence, 

oxygen, submarine light and 

nitrate measured continuously

10 50-km segments

@ 14 kt, 122-m depth:

2 Atlantic side NP,

2 Pacific side NP,

6 Pacific side @ 260-km spacing,

Remainder continuous 

at transit speed

18 extra XCTDs

@ 60-km spacing

= 1080 km

= 9.7 deg of lat Chlorophyll fluorescence, 

oxygen, submarine light and 

nitrate measured continuously

 Particulate material

 frozen every 2 hrs

 Carbon system every 2 hrs

Vertical sampling for discrete 

samples as for chemistry:

5-6 depth stairstep extending 

from surface mixed layer to 

230 m at XCTD stations

 Concentrate sampling across 

the ice edge in Jun–Sep

20 50-km segments

@ 14 kt, 122-m depth:

 2 Atlantic side NP,

 2 Pacific side of NP,

16 Pacific side @ 70-km spacing,

Remainder continuous

at transit speed

36 extra XCTDs

@ 40-km spacing

= 1440 km

= 12.9 deg of lat

30 50-km segments

@ 14 kt, 122-m depth:

2 Atlantic side of NP,

2 Pacific side of NP,

26 Pacific side @ 25-km spacing,

Remainder continuous

at transit speed

54 extra XCTDs

@ 40-km spacing

= 2160 km

= 19.5 deg of lat

40 50-km segments

@ 14 kt, 122-m depth:

2 Atlantic side NP,

Continuous Pacific side

72 extra XCTDs

@ 50-km spacing

= 2880 km

= 25.9 deg of lat
50

Table A-8. Ice-Camp Transit: Recent SCICEX Track

Sampling 

Corridor

Time Required (days)

Priority Ship’s Parameters Comments Revisit

Frequency

Transit Science Total 

1

1 0 1

All: 1

All: 

1 per 2 years for 

either North Pole 

Track or recent 

SCICEX Track

1 0.5 1.5

1 1 2

1 1.5 2.5
51

Science Priorities

Bathy Ice

Ocean

Hydrography Chemistry Biology

Continuous

Continuous at transit speed 

General approach:

Deploy XCTDs with finer 

resolution over Lomonosov R,

coarser resolution over 

Amundsen B and Canadian B 18O, salinity, nutrients 

(frozen) hourly

Transient tracers every 2 hrs

18O, salinity, nutrients (frozen) 

from mixed layer at each 

XCTD station

 Underway radium sampling

Vertical sampling suite:

(Estimated time: 12–18 hrs)

5–6 depth stairstep extending 

from surface mixed layer to 

230 m at approximately

 12–16 XCTD stations evenly 

distributed along track

Chlorophyll fluorescence, 

oxygen, submarine light and 

nitrate measured continuously

10 50-km segments

@ 14 kt, 122-m depth:

4 in region nearest NP,

6 Pac side @ 260-km spacing,

Remainder continuous

at transit speed

18 extra XCTDs

@ 60-km spacing

= 1080 km

= 9.7 deg of lat

Chlorophyll fluorescence, 

oxygen, submarine light and 

nitrate measured continuously

 Particulate material

 frozen every 2 hrs

 Carbon system every 2 hrs

Vertical sampling for discrete 

samples as for chemistry:

5–6 depth stairstep extending 

from surface mixed layer to 

230 m at XCTD stations

 Concentrate sampling across 

the ice edge in Jun–Sep

20 50-km segments

@ 14 kt, 122-m depth:

4 in region nearest NP,

16 Pacific side @ 70-km spacing,

Remainder continuous

at transit speed 

36 extra XCTDs

@ 40-km spacing

= 1440 km

= 12.9 deg of lat

30 50-km segments

@ 14 kt, 122-m depth:

2 Atlantic side of NP,

2 Pacific side of NP,

26 Pacific side @ 25-km spacing,

Remainder continuous

at transit speed

54 extra XCTDs

@ 40-km spacing

= 2160 km

= 19.5 deg of lat
52

Table A- 9. Ice-Camp Transit: Canadian Margin Track

Sampling 

Corridor

Time Required (days)

Priority Ship’s Parameters Comments Revisit

Frequency

Transit Science Total 

3

0.5 0 0.5

Ice: 2

Hydro: 3

Chem: 2

Bio: 3

Ice: 1 per 2 years

Hydro: 1 per 2 years

Chem: 1 per 2 years

Bio: 1 per 2 years

0.5 0.5 1

0.5 1 1.5

0.5 1.5 2

0.5 2 2.5
53

Science Priorities

Bathy Ice

Ocean

Hydrography Chemistry Biology

Choose an Alpha Ridge line; Otherwise continuous

Continuous at transit speed 

General approach:

Focus XCTDs first 

on middle segment 

(87°N 60°W to 80°N 130°W 

is approx 1000 km)

18O, salinity, nutrients 

(frozen) hourly

Transient tracers every 2 hrs

18O, salinity, nutrients (frozen) 

from mixed layer at each 

XCTD station

Underway radium sampling

Vertical sampling suite:

(Estimated time: 12–18 hrs)

5–6 depth stairstep extending 

from surface mixed layer to 

230 m at approximately

 12–16 XCTD stations evenly 

distributed along track

Chlorophyll fluorescence, 

oxygen, submarine light and 

nitrate measured continuously

10 50-km segments

@ 14 kt, 122-m depth

@ 170-km spacing

Remainder continuous

at transit speed

18 extra XCTDs

@ 60-km spacing

 = 1080 km Chlorophyll fluorescence, 

oxygen, submarine light and 

nitrate measured continuously

 Particulate material

 frozen every 2 hrs

 Carbon system every 2 hrs

Vertical sampling for discrete 

samples as for chemistry:

5–6 depth stairstep extending 

from surface mixed layer to 

230 m at XCTD stations

 Concentrate sampling across 

the ice edge in Jun–Sep

20 50-km segments

@ 14 kt, 122-m depth

@ 60-km spacing

Remainder continuous

at transit speed 

36 extra XCTDs

@ 40-km spacing

= 1440 km

30 50-km segments

@ 14 kt, 122-m depth

@ 25-km spacing

Remainder continuous

at transit speed

54 extra XCTDs

@ 40-km spacing

= 2160 km

Continuous

14 kt, 122-m depth

72 extra XCTDs

@ 50-km spacing

= 2880 km

 (transit from 84°N 15°E 

to 72°N 145°W is 

approx 2600 km)
54

 Appendix B

Original SCICEX

Memorandum of Agreement
55
56
57
58
59
60
61
62

 Appendix C

Current (Phase II) SCICEX

Memorandum of Agreement
63
64
65
66
67
68
69
70
71
72
73
74
75

 Appendix D

Acronyms

ACEX ............... Arctic Coring Expedition

AGAVE ............ Arctic Gakkel Vents

AMORE ........... Arctic Mid-Ocean Ridge Expedition 

AON................. Arctic Observing Network

ASL ................... Navy’s Arctic Submarine Laboratory

ATOC............... Acoustic Thermometry of Ocean Climate

AW.................... Atlantic Water

BGEP................ Beaufort Gyre Exploration Project

CDOM ............. Colored Dissolved Organic Matter

CFC .................. Chlorofluorocarbon

CTD.................. Conductivity, Temperature, Depth Sensor

DOC................. Dissolved Organic Carbon

DOM................ Dissolved Organic Matter

HOTRAX......... Healy-Oden Trans-Arctic Expedition

IAC ................... Interagency Committee

IARPC.............. Interagency Arctic Research Policy Committee

ICEX................. Ice Exercise

MOA................. Memorandum of Agreement

NASA ............... National Aeronautics and Space Administration

NSF................... National Science Foundation

NOAA.............. National Oceanic and Atmospheric Administration

NSIDC.............. National Snow and Ice Data Center

ONR ................. Office of Naval Research

PETM............... Paleocene/Eocene Thermal Maximum

RLGN............... Ring-Laser Gyro Navigation

SAC................... Science Advisory Committee

SAM.................. Science Accommodation Mission

SCICEX............ SCience ICe EXercise

SEARCH.......... Study of Environmental Arctic Change
76

SRVS................. Submarine Remote Video System

TEMPALT........ Temporary Alteration (any alteration that provides given capabilities 

on a temporary basis in support of mission requirements)

TOC.................. Total Organic Carbon

USARC............. U.S. Arctic Research Commission

USGS................ U.S. Geological Survey

XCTD............... Expendable Conductivity, Temperature, Depth Sensor
Acknowledgements

Many are to be thanked for their contribution in the development of the SCICEX Science Plan, Part 1, including:

•	 US Arctic Research Commission for their unwavering and

enthusiastic support of the SCICEX Science Advisory Committee, 

including the facilitation of committee meetings and the 

publication of the science plan.

•	 George Newton, former Chair, US Arctic Research Commission,

who played a critical role in the establishment of the SCICEX 

program and continues to provide strong advocacy for its 

continuation, for his key insights and guidance in the development 

of the science plan.

•	 US Navy for the spectacular photographs of submarines operating

under Arctic conditions.

•	 Ellen Kappel and Johanna Adams at Geosciences Professional

Services, Inc, for transforming the text of the science plan into a 

handsome publication we can all be proud of.

•	 Those who responded to the call for a community review of

the science plan and provided input that resulted in substantial 

improvements to the science plan: Lou Codispodi (University 

of Maryland Center for Environmental Sciences), Cathy Geiger 

(University of Delaware), Kelly Falkner (Oregon State Univeristy), 

Tim Hollibaugh (University of Georgia), Dave Kadko (Univeristy of 

Miami), David Kirchman (University of Delaware), Heide Mairs (on 

behalf of ExxonMobil’s sea ice group), Wieslaw Maslowski (Naval 

Postgraduate School, Monterey, CA), Jamie Morison (Polar Science 

Center, University of Washington), Robin Muench (Earth and 

Space Research, Seattle, WA), Drew Rothrock (Polar Science Center, 

University of Washington), Michael Steele (Polar Science Center, 

University of Washington), Wayne Sternberger (Johns Hopkins 

University Applied Physics Lab) 

•	 Jeff Gossett, US Navy Arctic Submarine Laboratory, for

providing critical technical leadership in the development of 

the Planning Matrix to ensure that the SCICEX Science Plan was 

operationally feasible.
SCICEX: Science Ice Exercise | http://www.scicex.org

June 2010