bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ice-sheet elevation changes caused by variations of the firn compaction rate induced by satellite-observed temperature variations (1982–2003)
Authors: Li Jun , Zwally H. Jay , Comiso Josefino C. 
Published: December 2007

AbstractChanges in the surface elevation of the Greenland and Antarctic ice sheets and ice shelves caused by variations in the rate of firn compaction are calculated with a time-dependent firn densification model driven by two decades (1982–2003) of satellite-observed monthly surface temperatures. The model includes the effects of melting and refreezing, both the direct changes in density and the subsequent effects on the densification rate. As previously shown, the temperature-dependent rate of densification is largest in summer, but changes in winter temperatures also have a significant effect. Over the last decade, climate warming has enhanced the rate of compaction and lowered the average surface elevation of Greenland by 1.8 cma-1 and most of West Antarctica by 1.9 cma–1. In East Antarctica, a small cooling raised the average surface elevation by 0.14 cma–1.
Integrated monitoring of mountain glaciers as key indicators of global climate change: the European Alps
Authors: Haeberli Wilfried , Hoelzle Martin , Paul Frank , Zemp Michael 
Published: December 2007

AbstractThe internationally recommended multi-level strategy for monitoring mountain glaciers is illustrated using the example of the European Alps, where especially dense information has been available through historical times. This strategy combines in situ measurements (mass balance, length change) with remote sensing (inventories) and numerical modelling. It helps to bridge the gap between detailed local process-oriented studies and global coverage. Since the 1980s, mass balances have become increasingly negative, with values close to –1mw.e. a–1 during the first 5 years of the 21st century. The hot, dry summer of 2003 alone caused a record mean loss of 2.45 mw.e., roughly 50% above the previous record loss in 1998, more than three times the average between 1980 and 2000 and an order of magnitude more than characteristic long-term averages since the end of the Little Ice Age and other extended periods of glacier shrinkage during the past 2000 years. It can be estimated that glaciers in the European Alps lost about half their total volume (roughly 0.5% a–1) between 1850 and around 1975, another 25% (or 1%a–1) of the remaining amount between 1975 and 2000, and an additional 10–15% (or 2–3% a–1) in the first 5 years of this century.
Changes in speed near the onset of Bindschadler Ice Stream, West Antarctica
Authors: Winberry J. Paul , Anandakrishnan Sridhar , Smith Andrew M. 
Published: December 2007

AbstractIce-stream velocities can change rapidly. Understanding the spatial and temporal pattern of these changes and the forcings responsible is essential for predicting ice-sheet mass balance. Inland migration of the onset location will lead to more efficient drainage of inland ice. One way to monitor the stability of the onset location is to investigate changes in the velocity field. We report on the velocity near the onset of Bindschadler Ice Stream, West Antarctica, in 2002 and compare these data to the velocity measured in 1996. Mean annual velocities were determined by measuring the GPS position of markers during consecutive seasons. We compare our results with similar measurements from 1996 to investigate temporal changes in this ice-stream onset. Our results indicate that only minimal changes have occurred in the speed of the ice stream between 1996 and 2002.
Glacier change and climate forcing in recent decades at Gran Campo Nevado, southernmost Patagonia
Authors: Möller M. , Schneider C. , Kilian R. 
Published: December 2007

AbstractDigital terrain models of the southern Chilean ice cap Gran Campo Nevado reflecting the terrain situations of the years 1984 and 2000 were compared in order to obtain the volumetric glacier changes that had occurred during this period. The result shows a slightly negative mean glacier change of 3.80 m. The outlet glacier tongues show a massive thinning, whereas the centre of the ice cap is characterized by a moderate thickening. Thus a distinct altitudinal variability of the glacier change is noticed. Hypothetically this could be explained by the combined effects of increased precipitation and increased mean annual air temperature. Both to verify and to quantify this pattern of climatic change, the mean glacier change as well as its hypsometric variation are compared with the results of a degree-day model. The observed volumetric glacier change is traced back to possible climate forcing and can be linked to an underlying climate change that must be comparable with the effects of a precipitation offset of at least 7–8% and a temperature offset of around 0.3 K compared to the steady-state conditions in the period 1984–2000.
Antarctic sea ice: a self-organizing map-based perspective
Authors: Reusch David B. , Alley Richard B. 
Published: December 2007

AbstractSelf-organizing maps (SOMs) provide a powerful, non-linear technique to optimally summarize a complex geophysical dataset using a user-selected number of ‘icons’ or SOM states, allowing rapid identification of preferred patterns, predictability of transitions, rates of transitions, and hysteresis in cycles. The use of SOMs is demonstrated here through application to a 24 year dataset (1973–96) of monthly Antarctic sea-ice edge positions. Variability in sea-ice extent, concentration and other physical characteristics is an important component of the Earth’s dynamic climate system, particularly in the Southern Hemisphere where annual changes in sea-ice extent (temporarily) double the size of the Antarctic cryosphere. SOM-based patterns concisely capture the spatial and temporal variability in these data, including the annual progression of expansion and retreat, a general eastward propagation of anomalies during the winter, and sub-annual variability in the rate of change in extent at different times of the year (e.g. retreat in January is faster than in November). There is also often a general seasonal hysteresis, i.e. monthly anomalies during cooling follow a different spatial path than during warming.
20th-century glacier fluctuations on Disko Island (Qeqertarsuaq), Greenland
Authors: Yde Jacob C. , Knudsen N. Tvis 
Published: December 2007

AbstractThis study assesses glacier fluctuations on Disko Island (Qeqertarsuaq), central West Greenland, during the 20th century. A total of 247 glaciers, of which 75 are classified as surge-type glaciers, are included, representing about 95% of the glacierized area. Based on expedition accounts and early maps, it is concluded that recession rates were highest during the first half of the century. Between 1953 and 2005, 70% of the glaciers showed recession, 28% remained stationary and 2% experienced overall advance due to glacier surging. The mean recession rate of quiescent surge-type glaciers was 20 ma–1 compared to 8ma–1 for normal glaciers. Identification of changes in glacier length controlled by climate changes is achieved by excluding surge-type glaciers from the dataset. The result indicates that glaciers with ablation areas facing in the arc south to northwest, covering an area above 5 km2 and having a terminus elevation below 800 m are the most climate-sensitive.
Fast computation of a viscoelastic deformable Earth model for ice-sheet simulations
Authors: Bueler Ed , Lingle Craig S. , Brown Jed 
Published: December 2007

AbstractThe model used by Lingle and Clark (1985) to approximate the deformation of the Earth under a single ice stream is adapted to the purposes of continent-scale ice-sheet simulation. The model combines a layered elastic spherical Earth (Farrell, 1972) with a viscous half-space overlain by an elastic plate lithosphere (Cathles, 1975). For the half-space model we identify a new mathematical formulation, essentially a time-dependent partial differential equation, which generalizes and improves upon the standard elastic plate lithosphere with relaxing asthenosphere model widely used in ice-sheet simulation. The new formulation allows a significantly faster numerical strategy, a spectral collocation method based directly on the fast Fourier transform. We verify this method by comparing to an integral formula for a disk load. We also demonstrate that the magnitudes of numerical errors made in approximating coupled ice-flow/Earth-deformation systems are significantly smaller than pairwise differences between several Earth models. Our implementation of the Lingle and Clark (1985) model offers important features of spherical, layered, self-gravitating, viscoelastic Earth models without the computational expense.
Some aspects of ice phenology on ponds in central Alaska, USA
Authors: Jeffries Martin O. , Morris Kim 
Published: December 2007

AbstractIce phenology (freeze-up, break-up and duration) was monitored for five seasons between autumn 2001 and spring 2006 at 11 small, shallow ponds in the boreal forest of central Alaska, USA. The sequence in which freeze-up (FU; day of 100% ice cover) and break-up (BU; day of zero ice cover) occurred at the 11 ponds showed moderately high to very high coherence each season. This was probably due to FU and BU being poorly correlated with pond morphometry (area, depth). BU is strongly correlated with April mean air temperature; a ±1˚C change in mean April air temperature is equivalent to a ±1.86 day change in BU. FU and air-temperature relationships are inconclusive, primarily because post-FU warm intervals in two autumns cause an anticorrelation between mean September air temperature and FU. Mean ice duration varies between 205 and 225 days, and is strongly correlated with maximum ice thickness through its effect on BU. A ±10mm change in maximum ice thickness will cause a ±0.6 day change in ice duration. Maximum ice thickness and ice composition (snow ice, congelation ice) also have a strong influence on break-up when all data from all ponds and all years are considered. The predictability of FU and BU sequence, the minor role of morphometry in FU and BU, the strong role of April mean air temperature in BU, and the role of maximum ice thickness in duration suggests that these ponds would be good sites for continued long-term observation of phenology and the influence of weather/climate variation and change, and for freeze-up/break-up process studies, particularly the role of ice composition and albedo.
Polynya Signature Simulation Method polynya area in comparison to AMSR-E 89GHz sea-ice concentrations in the Ross Sea and off the Adélie Coast, Antarctica, for 2002–05: first results
Authors: Kern Stefan , Spreen Gunnar , Kaleschke Lars , De La Rosa Sara , Heygster Georg 
Published: December 2007

AbstractThe Polynya Signature Simulation Method (PSSM) is applied to Special Sensor Microwave/Imager observations from different Defense Meteorological Satellite Program spacecraft for 2002–05 to analyze the polynya area in the Ross Sea (Ross Ice Shelf polynya (RISP) and Terra Nova Bay polynya (TNBP)) and off the Adélie Coast (Mertz Glacier polynya (MGP)), Antarctica, on a sub-daily scale. The RISP and the MGP exhibit similar average total polynya areas. Major area changes (>10000km2; TNPB: >2000km2) occur over a range of 2–3 to 20 days in all regions. Sub-daily area changes are largest for the MGP (5800km2) and smallest for the TNBP (800km2), underlining the persistence of the forcing of the latter. ARTIST sea-ice (ASI) algorithm concentration maps obtained using 89 GHz Advanced Microwave Scanning Radiometer (AMSR-E) data are compared to PSSM maps, yielding convincing agreement in the average, similarly detailed winter polynya distribution. Average ASI algorithm ice concentrations take values of 25–40% and 65–80% for the PSSM open-water and thin-ice class, respectively. The discrepancy with expected values (0% and 100%) can be explained by the different spatial resolution and frequency used by the methods. A new land mask and a mask to flag icebergs are introduced. Comparison of PSSM maps with thermal ice thickness based on AVHRR infrared temperature and ECMWF ERA-40 data suggests an upper thickness limit for the PSSM thin-ice class of 20–25 cm.
An improved numerical scheme to compute horizontal gradients at the ice-sheet margin: its effect on the simulated ice thickness and temperature
Authors: Saito Fuyuki , Abe-Ouchi Ayako , Blatter Heinz 
Published: December 2007

AbstractIn three-dimensional numerical ice-sheet models that use finite-difference schemes, the position of ice margins is poorly represented with a regular quadratic grid. As a result, in a centered difference scheme, the surface gradient term and the flux divergence term computed for the gridpoints next to the ice margin may be inaccurate. In this paper, an improved scheme is presented that computes the horizontal gradients at the ice-sheet margin using an asymmetric (upstream) second-order difference scheme in order to avoid using information from the zero-thickness gridpoints. The model is applied to an idealized synthetic geometry to obtain a steady-state ice-sheet topography. The improved model shows a realistically smooth thickness distribution near the margin. Thermomechanical coupling is found to enhance the error near the margin. The error in simulated thicknesses with the centered-difference method was significantly reduced with the new upstream scheme.
Relation between glacier-termini variations and summer temperature in Iceland since 1930
Authors: Sigurđsson Oddur , Jónsson Trausti , Jóhannesson Tómas 
Published: December 2007

AbstractMeasurements of the retreat and advance of glacier termini are simple and straightforward and in many cases give clear indications about climate history. A careful analysis of glacier type and the processes that override the climate forcing of the mass balance are important for the correct interpretation of terminus variations in terms of climate fluctuations. Regular measurements of glacier variations in Iceland were started in 1930. The Iceland Glaciological Society is now responsible for the monitoring programme. The observed front variations of non-surge-type outlet glaciers of various sizes have closely mimicked major variations of the climate in Iceland during the 20th century. Most of the glaciers retreated rapidly during the warm decades from 1930 to 1960, slowing down as the climate cooled during the following decade, and started to advance after 1970. The rate of advance peaked in the 1980s, after which it slowed down as a consequence of rapid warming of the climate that has taken place since the mid-1980s. Mass-balance measurements show alternating positive and negative mass balance of glaciers during the period 1987–95, but the mass balance has been predominantly negative since 1996. Most glaciers in Iceland began to retreat after 1990, and by 2000 all monitored non-surge-type glaciers in Iceland were retreating. A comparison of the front variations of non-surge-type glaciers and mean summer temperature shows that the major shifts in the climate were followed by a change in the rate of advance or retreat at the termini with a delay of only a few years. This delay does not seem to correlate with the size, the mass turnover or other characteristics of the glacier.
A late-winter to early-spring temperature reconstruction for southeastern Norway from 1758 to 2006
Authors: Nordli Ø. , Lundstad E. , Ogilvie A.E.J. 
Published: December 2007

AbstractSystematic temperature observations were not undertaken in Norway until the early 19th century, and even then only sporadically. Climate-proxy data may be used to reconstruct temperatures before this period, but until now there have not been any climate proxies available for late winter. This situation has recently changed, as a diary containing historical ice break-up data from a farm near lake Randsfjord in southeastern Norway has been discovered. These data, together with observations from lake Mjøsa in the same region, make it possible to reconstruct temperature back to 1758. The reconstructed series, combined with instrumental series from the area near the lake, were merged into one composite time series covering the period 1758–2006. The lowest temperatures are seen during the Dalton sunspot minimum in the early 19th century. The 20th century was 1.3˚C warmer than the 19th century, whereas the 19th century was 0.4˚C warmer than the last 43 years of the 18th century. During the period 1758–1850, the mean temperature was 1.4˚C lower than the mean value of the 20th century. The warmth observed in the 1990s and at the start of the 21st century is unprecedented during the whole series.
Recent air-temperature changes in the Arctic
Authors: Przybylak Rajmund 
Published: December 2007

AbstractA detailed analysis of the spatial and temporal changes in mean seasonal and annual surface air temperature (SAT) in the Arctic is presented mainly for the period 1951–2005. Mean seasonal and annual homogenized and complete series of SAT from up to 35 Arctic stations were used in the analysis. The focus in this paper is on the 11 years 1995–2005, a period which saw dramatic warming in the Arctic (>1˚C for annual values in relation to the 1951–90 mean). An abrupt rise in SAT occurred in the mid-1990s and was most pronounced in autumn and winter (>2˚C). The greatest warming in the period 1995–2005 occurred in the Pacific and Canadian regions (>1˚C), while the lowest was in the Siberian region (0.82˚C). This period has been the warmest since at least the 17th century. In particular, 2005 was an exceptionally warm year (>2˚C in relation to the 1951–90 mean) and was warmer than 1938, the warmest year in the 20th century. The seasonal and annual trends of the areally averaged Arctic SAT for the periods 1936–2005, 1951–2005 and 1976–2005 are positive, with the exception of winter and autumn for the first period. The majority of trends calculated for the last two periods are statistically significant. While there are varying opinions about the forces driving the present warming, it seems likely that the marked rise in SAT in the mid-1990s (mainly from 1994 to 1995) was caused by (i) a set of natural factors, (ii) non-linear effects of greenhouse-gas loading, or (iii) the combined effect of these two groups of factors.
Surface melting derived from microwave radiometers: a climatic indicator in Antarctica
Authors: Picard G. , Fily M. , Gallee H. 
Published: December 2007

AbstractThis paper aims at presenting a new dataset including the melt events derived from microwave remote sensing occurring in Antarctica from summer 1979/80 to 2005/06. The method for detecting melt events and sources of error is presented, and then trends in melt duration for every pixel are extracted from the dataset, mapped and analyzed. The analysis focuses on two particular cases, and the main results show that: (1) the trends over the period 1980–2006 in the Antarctic Peninsula match with lengthening of the melt season on the ice shelves and, surprisingly, shortening of the melt season in the mountainous area of the peninsula; and (2) the trends over the period 1996–2006 on the entire continent show a dipolar pattern, with the western regions experiencing decreasing melt duration, whereas East Antarctica and the Ross Ice Shelf experience increasing melt duration. This pattern closely mirrors the temperature pattern expected when the Southern Annular Mode is in a decreasing trend, as it is over the period 1996–2006. For further analysis and validation, the dataset has been made available at http://www-lgge.obs.ujf-grenoble.fr/~picard/melting/.
Glacier changes in the west Kunlun Shan from 1970 to 2001 derived from Landsat TM/ETM+ and Chinese glacier inventory data
Authors: Shangguan Donghui , Liu Shiyin , Ding Yongjian , Li Jing , Zhang Yong , Ding Lianfu , Wang Xing , Xie Changwei , Li Gang 
Published: December 2007

AbstractRecent studies have indicated that widespread wastage of glaciers in western China has occurred since the late 1970s. By using digitized glacier outlines derived from the 1970 inventory and Landsat satellite data from 1990/91 to 2001, we obtained area changes of about 278 glaciers with a total area of 2711.57 km2 in the heavily glaciated west Kunlun Shan (WKS) in the northern Tibetan Plateau (TP). Results indicate that the prevailing characteristic of glacier variation is ice wastage, and glacier area decreased by 10 km2 (0.4% of the total 1970 area) between 1970 and 2001. Both the south and north slopes of the WKS presented shrinkage during 1970–2001, but whereas on the north slope a slight enlargement of ice extent during 1970–90 was followed by a reduction of 0.2% during 1990–2001, on the south slope the glacier area decreased by 1.2% during 1970–91, with a small increment of 0.6% during 1991–2001. Comparisons with other glaciated mountainous regions in western China show that glaciers in the research area have experienced less retreat. Based on records from the Guliya ice core, we believe that an increase in air temperature was the main forcing factor for glacier shrinkage during 1970–2001.
Ice-volume changes of selected glaciers in the Swiss Alps since the end of the 19th century
Authors: Bauder Andreas , Funk Martin , Huss Matthias 
Published: December 2007

AbstractThe evolution of surface topography of glaciers in the Swiss Alps is well documented with high-resolution aerial photographs repeatedly recorded since the 1960s and further back in time with topographic maps including elevation contour lines first surveyed in the mid-19th century. In order to quantify and interpret glacier changes in the Swiss Alps, time series of volume changes over the last 100–150 years have been collected. The available datasets provide a detailed spatial resolution for the retreat period since the end of the Little Ice Age. The spatial distribution as well as temporal variations of the thickness change were analyzed. A significant ice loss since the end of the 19th century was observed in the ablation area, while the changes in the accumulation area were small. We found moderate negative secular rates until the 1960s, followed by steady to positive rates for about two decades and strong ice loss starting in the 1980s which has lasted until the present. An evaluation of 19 glaciers revealed a total ice volume loss of about 13km3 since the 1870s, of which 8.7 km3 occurred since the 1920s and 3.5 km3 since 1980. Decadal mean net balance rates for the periods 1920–60, 1960–80 and 1980–present are –0.29, –0.03 and –0.53ma–1w.e., respectively.
Recent changes in glacier area and volume within the southern Canadian Cordillera
Authors: DeBeer Christopher M. , Sharp Martin J. 
Published: December 2007

AbstractNet changes in glacier area in the region 50–51˚ N, 116–125˚W, which includes the Columbia and Rocky Mountains (1951/52–2001) and the Coast Mountains (1964/65–2002), were determined through a comparison of historic aerial photography and contemporary Landsat 7 ETM+ imagery. The volumes of individual glaciers were estimated using an empirical volume–area scaling relationship. The area of glaciers in the Coast Mountains decreased by 120±10km2, or 5%of the initial ice-covered area here. The areas of glaciers in the Columbia and Rocky Mountains decreased by 20 and 6km2 respectively, corresponding to relative changes in total area of –5% and –15%. The estimated total ice volume loss from the whole region was 13 ±3 km3. In all parts of the study area, the relative changes in area of individual glaciers showed considerable variability, while the smallest glaciers remained essentially unchanged. This suggests that local factors unique to individual glaciers largely determine their sensitivity to climatic change, and that the very small glaciers are collectively less sensitive to such change.