bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass balance of Devon Ice Cap, Canadian Arctic
Authors: Shepherd Andrew , Du Zhijun , Benham Toby J. , Dowdeswell Julian A. , Morris Elizabeth M. 
Published: December 2007

AbstractInterferometric synthetic aperture radar data show that Devon Ice Cap (DIC), northern Canada, is drained through a network of 11 glacier systems. More than half of all ice discharge is through broad flows that converge to the southeast of the ice cap, and these are grounded well below sea level at their termini. A calculation of the ice-cap mass budget reveals that the northwestern sector of DIC is gaining mass and that all other sectors are losing mass. We estimate that a 12 489 km2 section of the main ice cap receives 3.46±0.65 Gt of snowfall each year, and loses 3.11±0.21 Gt of water through runoff, and 1.43±0.03 Gt of ice through glacier discharge. Altogether, the net mass balance of DIC is –1.08±0.67 Gt a–1. This loss corresponds to a 0.003 mma–1 contribution to global sea levels, and is about half the magnitude of earlier estimates.
Volume–area scaling vs flowline modelling in glacier volume projections
Authors: Radić Valentina , Hock Regine , Oerlemans Johannes 
Published: December 2007

AbstractVolume–area scaling provides a practical alternative to ice-flow modelling to account for glacier size changes when modelling the future evolution of glaciers; however, uncertainties remain as to the validity of this approach under non-steady conditions. We address these uncertainties by deriving scaling exponents in the volume–area relationship from one-dimensional ice-flow modelling. We generate a set of 37 synthetic steady-state glaciers of different sizes, and then model their volume evolution due to climate warming and cooling as prescribed by negative and positive mass-balance perturbations, respectively, on a century timescale. The scaling exponent derived for the steady-state glaciers (γ = 1.56) differs from the exponents derived for the glaciers in transient (non-steady) state by up to 86%. Nevertheless, volume projections employing volume–area scaling are relatively insensitive to these differences in scaling exponents. Volume–area scaling agrees well with the results from ice-flow modelling. In addition, the scaling method is able to simulate the approach of a glacier to a new steady state, if mass-balance elevation feedback is approximated by removing or adding elevation bands at the lowest part of the glacier as the glacier retreats or advances. If area changes are approximated in the mass-balance computations in this way, our results indicate that volume–area scaling is a powerful tool for glacier volume projections on multi-century timescales.
Long-term change of mass balance and the role of radiation
Authors: Ohmura Atsumu , Bauder Andreas , Müller Hans , Kappenberger Giovanni 
Published: December 2007

AbstractThe effect of climate change in the 20th century is investigated based on measured mass-balance data. Annual, winter and summer mass balances on Claridenfirn, Switzerland, (since 1914/15) Storglaciären, Sweden, (since 1945/46) Storbreen, Norway, (since 1948/49) Glacier de Sarennes, France, (since 1948/49) and Vernagtferner, Austria, (since 1965/66) are studied with air temperature at high-altitude stations and the longest records of solar global radiation in Europe. The mean mass balances of these glaciers during the 20th century were mostly negative except for the first two decades. The fluctuating mass balance reaches the minimum (largest loss) and maximum (almost equilibrium) around 1940 and 1980, respectively, with a drastic loss in the last 15 years. These variations are mostly steered by the variation in summer mass balance. The change in the summer mass balance is determined to 72% by temperature and the remaining 28% by solar radiation. During the colder period (e.g. 1960–80), the reduction in solar radiation counteracted the warming trend due to the greenhouse effect. Since 1990 the greenhouse effect of terrestrial radiation and the global brightening effect of solar radiation have both been acting to accelerate the melt, resulting in the unprecedented mass loss of the observational era. The glacier mass balance during the 20th century clearly reacted towards temperature and solar radiation changes, which reflected the greenhouse effect and aerosol and cloud variations.
Temperature variations over the past millennium on the Tibetan Plateau revealed by four ice cores
Authors: Yao Tandong , Duan Keqin , Thompson L.G. , Wang Ninglian , Tian Lide , Xu Baiqing , Wang Youqing , Yu Wusheng 
Published: December 2007

AbstractTemperature variation on the Tibetan Plateau over the last 1000 years has been inferred using a composite δ18O record from four ice cores. Data from a new ice core recovered from the Puruogangri ice field in the central Tibetan Plateau are combined with those from three other cores (Dunde, Guliya and Dasuopu) recovered previously. The ice-core δ18O composite record indicates that the temperature change on the whole Tibetan Plateau is similar to that in the Northern Hemisphere on multi-decadal timescales except that there is no decreasing trend from AD 1000 to the late 19th century. The δ18O composite record from the northern Tibetan Plateau, however, indicates a cooling trend from AD 1000 to the late 19th century, which is more consistent with the Northern Hemisphere temperature reconstruction. The δ18O composite record reveals the existence of the Medieval Warm Period and the Little Ice Age (LIA) on the Tibetan Plateau. However, on the Tibetan Plateau the LIA is not the coldest period during the last millennium as in other regions in the Northern Hemisphere. The present study indicates that the 20th-century warming on the Tibetan Plateau is abrupt, and is warmer than at any time during the past 1000 years.
Glacier mass-balance fluctuations in the Pacific Northwest and Alaska, USA
Authors: Josberger Edward G. , Bidlake William R. , March Rod S. , Kennedy Ben W. 
Published: December 2007

AbstractThe more than 40 year record of net and seasonal mass-balance records from measurements made by the United States Geological Survey on South Cascade Glacier, Washington, and Wolverine and Gulkana Glaciers, Alaska, shows annual and interannual fluctuations that reflect changes in the controlling climatic conditions at regional and global scales. As the mass-balance record grows in length, it is revealing significant changes in previously described glacier mass-balance behavior, and both inter-glacier and glacier–climate relationships. South Cascade and Wolverine Glaciers are strongly affected by the warm and wet maritime climate of the northeast Pacific Ocean. Their net balances have generally been controlled by winter accumulation, with fluctuations that are strongly related to the Pacific Decadal Oscillation (PDO). Recently, warm dry summers have begun to dominate the net balance of the two maritime glaciers, with a weakening of the correlation between the winter balance fluctuations and the PDO. Non-synchronous periods of positive and negative net balance for each glacier prior to 1989 were followed by a 1989–2004 period of synchronous and almost exclusively negative net balances that averaged –0.8m for the three glaciers.
Long-term change, interannual and intra-seasonal variability in climate and glacier mass balance in the central Greater Caucasus, Russia
Authors: Shahgedanova M. , Popovnin V. , Aleynikov A. , Petrakov D. , Stokes C.R. 
Published: December 2007

AbstractLong-term trends, interannual and intra-seasonal variability in the mass-balance record from Djankuat glacier, central Greater Caucasus, Russia, are related to local climate change, synoptic and large-scale anomalies in atmospheric circulation. A clear warming signal emerged in the central Greater Caucasus in the early 1990s, leading to a strong increase in ablation. In the absence of a compensating change in winter accumulation, the net mass balance of Djankuat has declined. The highest value of seasonal ablation on record was registered in the summer of 2000. At the beginning of the 21st century these trends reversed. Ablation was below average even in the summer of 2003, which was unusually warm in western Europe. Precipitation and winter accumulation were high, allowing for a partial recovery of net mass balance. The interannual variability in the components of mass balance is weakly related to the North Atlantic Oscillation (NAO) and the Scandinavian teleconnection patterns, but there is a clear link with the large-scale circulation anomalies represented by the Rossby pattern. Five synoptic categories have been identified for the ablation season of 2005, revealing a strong separation between components of radiation budget, air temperature and daily melt. Air temperature is the main control over melt. The highest values of daily ablation are related to the strongly positive NAO which forces high net radiation, and to the warm and moist advection from the Black Sea.
Investigations of meltwater refreezing and density variations in the snowpack and firn within the percolation zone of the Greenland ice sheet
Authors: Parry Victoria , Nienow Peter , Mair Douglas , Scott Julian , Hubbard Bryn , Steffen Konrad , Wingham Duncan 
Published: December 2007

AbstractThe mass balance of polythermal ice masses is critically dependent on the proportion of surface-generated meltwater that subsequently refreezes in the snowpack and firn. In order to quantify this effect and to characterize its spatial variability, we measured near-surface (<10 m) snow and firn densities at an elevation of ~1945ma.s.l. in the percolation zone of the Greenland ice sheet in spring and autumn 2004. Results indicate that local snowpack depth above the previous end-of-summer 2003 melt surface increased by ±5% (7.6 cm) from spring to autumn while, over the same period, snowpack density increased by >26%, resulting in a 32% increase in net accumulation. This ‘seasonal densification’ increased at lower elevations, rising to 47% 10 km closer to the ice-sheet margin at 1860ma.s.l. Density/depth profiles from nine sites within 1 km2 at ~1945ma.s.l. reveal complex stratigraphies that change over short spatial scales and seasonally. We conclude that estimates of mass-balance change cannot be calculated solely from observed changes in surface elevation, but that near-surface densification must also be considered. However, predicting spatial and temporal variations in densification may not be straightforward. Further, the development of complex firn-density profiles both masks discernible annual layers in the near-surface firn and ice stratigraphy and is likely to introduce error into radar-derived estimates of surface elevation.
Glacier changes in the Austrian Alps during the last three decades, derived from the new Austrian glacier inventory
Authors: Lambrecht A. , Kuhn M. 
Published: December 2007

AbstractBeginning in 1996, aerial photographs were taken for a new Austrian glacier inventory, resulting in digital elevation models (DEMs) and digital orthoimages. An earlier inventory of the Austrian glaciers containing the original aerial photographs and glacier maps and a manual evaluation of various glacier parameters as of 1969 has been re-evaluated at the present state of the art. The two inventories provide the basis for the comparison of glacier reactions over a period of 29 years. In general a reduction of glacier area is observed for almost all Austrian glaciers between 1969 and 1998. The overall reduction in ice-covered area is 17%. The glacier volume change calculated from the DEMs amounts to about 5 km3. This is almost 22% of the ice volume in Austria in 1969, estimated from a volume–area relation. Changes of individual glaciers, however, show a wide variability, depending on their size and physiographic setting.
Sea-ice thickness in the Weddell Sea, Antarctica: a comparison of model and upward-looking sonar data
Authors: Renner Angelika H.H. , Lytle Victoria 
Published: December 2007

AbstractSea-ice thickness is a key parameter for estimates of salt fluxes to the ocean and the contribution to global thermohaline circulation. Observations of sea-ice thickness in the Southern Ocean are sparse and difficult to collect. An exception to this data gap is time-series data from upward-looking sonars (ULS) which sample the drifting sea ice continuously. In this study we use ULS data from ten different locations over periods ranging from 9 to 25 months to compare with model data. Although these data are limited in space and time, they provide a qualitative indication of the ability of global climate models (GCMs) to adequately represent Southern Ocean sea ice. We compare the ULS data to output from four different GCMs (BCCR-BCM2.0, ECHAM5/MPI-OM, UKMO-HadCM3 and NCAR CCSM3) which were used for the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. They simulate the ice thickness reasonably well, but in most cases average model ice thickness is less than thicknesses derived from ULS data. The seasonal cycle produced by the models correlates well with the ULS except for locations near Maud Rise, where in summer the ULS find a low concentration of thick ice floes. This overly thin ice will have implications for both the salt flux to the central Weddell Sea during the growth season and the freshwater flux during the melt season. Using satellite-derived ice-drift data to calculate transports in the Weddell Sea, we find that the underestimation of ice thickness results in underestimated salt fluxes.
A time series of SAR data for monitoring changes in boundaries of glacier zones on the Antarctic Peninsula
Authors: Arigony-Neto Jorge , Rau Frank , Saurer Helmut , Jaña Ricardo , Simões Jefferson Cardia , Vogt Steffen 
Published: December 2007

AbstractDrastic changes have been detected in glacial systems of the Antarctic Peninsula in the last few decades and are well documented in numerous scientific publications. However, the spatial and temporal distribution of glacier changes on the Antarctic Peninsula remains largely restricted to ice fronts. To expand the current monitoring of a few glaciers, unevenly distributed along the peninsula, to a representative set, we developed a method to simplify the detection of boundaries between glacier zones using satellite SAR data. The evolution of glacier zones is greatly influenced by local and regional climatic and meteorological settings. Their variations in response to changes in energy or mass balance are considered as good indicators of climatic changes. In this paper, we describe the results of knowledge-based image analysis algorithms on test areas located at Trinity Peninsula and near Marguerite Bay. In general, the two analyzed areas show different patterns of glacier zone development. The bare-ice zone occurs mainly on glaciers located on the eastern side of Trinity Peninsula. Its upper boundary shows a good correlation with the mean summer air temperature. Finally, the position of the dry-snow line shows different spatial patterns of change in both study areas.
The response of a simple Antarctic ice-flow model to temperature and sea-level fluctuations over the Cenozoic era
Authors: Van Tuyll C.I. , Van De Wal R.S.W. , Oerlemans J. 
Published: December 2007

AbstractAn ice-flow model is used to simulate the Antarctic ice-sheet volume and deep-sea temperature record during Cenozoic times. We used a vertically integrated axisymmetric ice-sheet model, including bedrock adjustment. In order to overcome strong numerical hysteresis effects during climate change, the model is solved on a stretching grid. The Cenozoic reconstruction of the Antarctic ice sheet is accomplished by splitting the global oxygen isotope record derived from benthic foraminifera into an ice-volume and a deep-sea temperature component. The model is tuned to reconstruct the initiation of a large ice sheet of continental size at 34 Ma. The resulting ice volume curve shows that small ice caps (<107 km3) could have existed during Paleocene and Eocene times. Fluctuations during the Miocene are large, indicating a retreat back from the coast and a vanishing ice flux across the grounding line, but with ice volumes still up to 60% of the present-day volume. The resulting deep-sea temperature curve shows similarities with the paleotemperature curve derived from Mg/Ca in benthic calcite from 25 Ma till the present, which supports the idea that the ice volume is well reproduced for this period. Before 34 Ma, the reproduced deep-sea temperature is slightly higher than is generally assumed. Global sea-level change turns out to be of minor importance when considering the Cenozoic evolution of the ice sheet until 5 Ma.
River-ice break-up/freeze-up: a review of climatic drivers, historical trends and future predictions
Authors: Prowse T.D. , Bonsal B.R. , Duguay C.R. , Lacroix M.P. 
Published: December 2007

AbstractRiver ice plays a fundamental role in biological, chemical and physical processes that control freshwater regimes of the cold regions. Moreover, it can have enormous economic implications for river-based developments. All such activities and processes can be modified significantly by any changes to river-ice thickness, composition or event timing and severity. This paper briefly reviews some of the major hydraulic, mechanical and thermodynamic processes controlling river-ice events and how these are influenced by variations in climate. A regional and temporal synthesis is also made of the observed historical trends in river-ice break-up/freeze-up occurrence from the Eurasian and North American cold regions. This involves assessment of several hydroclimatic variables that have influenced past trends and variability in river-ice break-up/freeze-up dates including air-temperature indicators (e.g. seasonal temperature, 0˚C isotherm dates and various degree-days) and large-scale atmospheric circulation patterns or teleconnections. Implications of future climate change on the timing and severity of river-ice events are presented and discussed in relation to the historical trends. Attention is drawn to the increasing trends towards the occurrence of mid-winter break-up events that can produce especially severe flood conditions but prove to be the most difficult type of event to model and predict.
Assessing the possibility to couple the chemical signal in winter snow on Storglaciären, Sweden, to atmospheric climatology
Authors: Jansson Peter , Linderholm Hans W. , Pettersson Rickard , Karlin Torbjörn , Mörth Carl-Magnus 
Published: December 2007

AbstractWinter accumulation on glaciers in temperate to sub-arctic climate regimes is determined by both precipitation and snowdrifting during repeated events during any particular winter. Since glacier mass balance is calculated from the sum of winter and summer balance, and summer balance can be modeled with high accuracy, identification of the coupling between atmospheric circulation and winter balance is essential in order to fully understand the climate information hidden in the glacier mass-balance records. We have sampled snow cores from Storglaciären, Sweden, to examine identifiable chemical signatures to link these with up-wind sources in an attempt to quantify how much accumulation occurs under given atmospheric conditions. The snow samples reveal that several different chemical signatures occur but that identifying their source is not trivial, although only few but distinct sources exist. The relationship between the identified strata of a given signature is difficult to couple to recorded precipitation events because the crucial timing of deposition is lacking in our investigation. If time control on snow deposition is available, the combination of snow chemistry, meteorological and climatological data is a promising tool for evaluating the coupling between snow accumulation and atmospheric circulation.
Recent glacier retreat in the Caucasus Mountains, Russia, and associated increase in supraglacial debris cover and supra-/proglacial lake development
Authors: Stokes C.R. , Popovnin V. , Aleynikov A. , Gurney S.D. , Shahgedanova M. 
Published: December 2007

AbstractThis paper reports changes in supraglacial debris cover and supra-/proglacial lake development associated with recent glacier retreat (1985–2000) in the central Caucasus Mountains, Russia. Satellite imagery (Landsat TM and ETM+) was used to map the surface area and supraglacial debris cover on six neighbouring glaciers in the Adylsu valley through a process of manual digitizing on a false-colour composite of bands 5, 4, 3 (red, green, blue). The distribution and surface area of supraglacial and proglacial lakes was digitized for a larger area, which extended to the whole Landsat scene. We also compare our satellite interpretations to field observations in the Adylsu valley. Supraglacial debris cover ranges from <5% to >25% on individual glaciers, but glacier retreat between 1985 and 2000 resulted in a 3–6% increase in the proportion of each glacier covered by debris. The only exception to this trend was a very small glacier where debris cover did not change significantly and remote mapping proved more difficult. The increase in debris cover is characterized by a progressive up-glacier migration, which we suggest is being driven by focused ablation (and therefore glacier thinning) at the up-glacier limit of the debris cover, resulting in the progressive exposure of englacial debris. Glacier retreat has also been accompanied by an increase in the number of proglacial and supraglacial lakes in our study area, from 16 in 1985 to 24 in 2000, representing a 57% increase in their cumulative surface area. These lakes appear to be impounded by relatively recently lateral and terminal moraines and by debris deposits on the surface of the glacier. The changes in glacier surface characteristics reported here are likely to exert a profound influence on glacier mass balance and their future response to climate change. They may also increase the likelihood of glacier-related hazards (lake outbursts, debris slides), and future monitoring is recommended.
Positive mass balance during the late 20th century on Austfonna, Svalbard, revealed using satellite radar interferometry
Authors: Bevan Suzanne , Luckman Adrian , Murray Tavi , Sykes Helena , Kohler Jack 
Published: December 2007

AbstractDetermining whether increasing temperature or precipitation will dominate the cryospheric response to climate change is key to forecasting future sea-level rise. The volume of ice contained in the ice caps and glaciers of the Arctic archipelago of Svalbard is small compared with that of the Greenland or Antarctic ice sheets, but is likely to be affected much more rapidly in the short term by climate change. This study investigates the mass balance of Austfonna, Svalbard’s largest ice cap. Equilibrium-line fluxes for the whole ice cap, and for individual drainage basins, were estimated by combining surface velocities measured using satellite radar interferometry with ice thicknesses derived from radio-echo sounding. These fluxes were compared with balance fluxes to reveal that during the 1990s the total mass balance of the accumulation zone was (5.6±2.0)×108m3 a–1. Three basins in the quiescent phase of their surge cycles contributed 75% of this accumulation. The remaining volume may be attributable either to as yet unidentified surge-type glaciers, or to increased precipitation. This result emphasizes the importance of considering the surge dynamics of glaciers when attempting to draw any conclusions on climate change based on snapshot observations of the cryosphere.