bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass-balance characteristics of arctic glaciers
Authors: Braithwaite Roger J. 
Published: November 2007

AbstractA survey of available mass-balance data shows that glaciers on arctic islands, i.e. mountain glaciers and ice caps in northern Canada, Greenland, Svalbard and the Eurasian islands, share mass-balance characteristics of low annual amplitude and small interannual variability. By contrast, glaciers around the Arctic (e.g. in Alaska, Iceland, mainland Scandinavia and northern Eurasia) can have exceptionally large annual amplitude and interannual variability but otherwise share characteristics with glaciers in lower latitudes. The arctic island glaciers occur in areas with low annual precipitation and high annual temperature variability, i.e. in dry-cold or continental regions. Most glaciers surrounding the Arctic (Alaska, Iceland and Scandinavia) occur in areas with high annual precipitation and low annual temperature variability, i.e. in wet-warm or maritime regions. Earlier mass-balance modelling showed that arctic island glaciers have low sensitivity to temperature changes consistent with their low mass-balance amplitude. However, very large changes in mass balance could occur on arctic island glaciers if the sea ice surrounding the arctic islands were reduced so that the climate of the arctic islands becomes more maritime.
The presence of thrust-block naled after a major surge event: Kuannersuit Glacier, West Greenland
Authors: Yde Jacob C. , Tvis Knudsen N. , Larsen Nicolaj K. , Kronborg Christian , Nielsen Ole B. , Heinemeier Jan , Olsen Jesper 
Published: November 2007

AbstractThrust-block naled in front of Kuannersuit Glacier, West Greenland, appears to have formed during the termination of a terrestrial surge event by a combination of enhanced winter runoff, rapid advance of the glacier terminus, and proglacial stress release by thrusting and stacking of naled blocks. This process is equivalent to the formation of thrust-block moraines. The thrust-block naled consists of at least seven thrust sheets, which are characterized by stratified ice with beds composed of a lower debris-rich lamina, an intermediate dispersed lamina and a top clean-ice lamina, and underlain by frozen outwash deposits. The thrust-block naled differs from basal stratified ice in the absence of internal deformation structures, a relatively low debris concentration, a clay-rich particle-size distribution and a preferential sorting of lighter minerals. The oxygen isotope composition of the thrust-block naled is indistinguishable from δ18O values from meteoric glacier ice and bulk meltwater, but different from basal stratified ice facies. The d–δD relationship indicates that thrust-block naled has been formed by freezing of successive thin layers of bulk waters with variable isotopic composition, whereas basal stratified ice has developed in a subglacial environment with regelation. This work shows that the association between proglacial naled and rapidly advancing glaciers may have significant consequences for the proglacial geomorphology and the interpretation of basal ice layers.
Flow field of Kronebreen, Svalbard, using repeated Landsat 7 and ASTER data
Authors: Kääb Andreas , Lefauconnier Bernard , Melvold Kjetil 
Published: November 2007

AbstractKnowledge about the spatio-temporal distribution of fast-flowing Arctic glaciers is still limited. Kronebreen, Svalbard, in particular, includes the confluence − and the dynamic interplay − of the fast-flowing Kronebreen and the currently slow-flowing Kongsvegen. In this study, image-matching techniques on the basis of repeated Landsat 7 Enhanced Thematic Mapper Plus (ETM+) pan and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite data are applied in order to derive surface velocity fields of the lowermost 10 km of Kronebreen for the annual periods 1999/2000, 2000/01, 2001/02 and a 40 day period around July 2001. This work perfectly complements differential synthetic aperture radar interferometry (DInSAR) studies available for Kronebreen. A complete surface velocity field is now available from combining the DInSAR studies for the upper part of the glacier and the optical image-matching study presented here. The data obtained within this study are also compared to velocity data of 1964, 1986, 1990 and 1996. As also suggested by previous studies, a significant spatio-temporal variability of the spring/summer and annual ice speeds becomes evident.
Palaeo-ice streams in the northern Keewatin sector of the Laurentide ice sheet
Authors: Angelis Hernán De , Kleman Johan 
Published: November 2007

AbstractEvidence for ice streams in the Laurentide ice sheet is widespread. In the region of northern Keewatin and the Boothia Peninsula, Nunavut, Canada, palaeo-ice streams have been recognized, but their location, size and potential role in ice-sheet dynamics are poorly constrained. Based on the interpretation of satellite imagery, we produce a palaeo-ice-stream map of this region. Glacial directional landforms, eskers and moraines were mapped and integrated into landform assemblages using a glacial geological inversion model. Palaeo-frozen bed areas were also identified. Relative age of the geomorphic swarms was assessed by cross-cutting relationships and radiocarbon ages where available. Using this information we obtained a glaciologically plausible picture of ice-stream evolution within the northernmost Laurentide ice sheet. On the M’Clintock Channel corridor, three generations of pure ice streams are found. On Baffin Island and the Gulf of Boothia, glaciation was dominated by frozen-bed zones located on high plateaus and ice streams running along the troughs, i.e. topographic ice streams. A massive convergent pattern at the head of Committee Bay drained ice from both the Keewatin and Foxe sectors and was probably one of the main deglaciation channels of the Laurentide ice sheet. Finally, our results indicate that streaming flow was present in the deep interior of the Laurentide ice sheet, as recently shown for the Greenland and Antarctic ice sheets.
Analyses of a surging outlet glacier of Vatnajökull ice cap, Iceland
Authors: Aðalgeirsdóttir Guðfinna , Björnsson Helgi , Pálsson Finnur , Magnússon Eyjolfur 
Published: November 2007

AbstractMany of the large outlet glaciers of Vatnajökull ice cap, Iceland, have a history of regular surges. The mass transport during surges can be up to 25% of the total ice flux. This is a considerable amount that affects the whole ice cap, the location of the ice divides, the flow field and the size and shape of the ice cap. Data from the surging outlet Dyngjujökull, on the northern side of Vatnajökull, which surged during the period 1998-2000, are presented: surface elevation changes, displacement and total mass tr ansport. The total gain in ice volume in the receiving area, due to the surge, is considerably smaller than the loss in the reservoir area. The difference is mainly due to enhanced melting rates on the larger surface area of the crevassed glacier surface, and increased turbulent fluxes above the surface, but also due to increased frictional melting at the bed during the surge. A two-dimensional vertically integrated numerical flow model, of standard shallow-ice approximation type, is used to show that a modeled glacier that is similar in size to Dyngjujökull and subject to the same mass balance has three times higher velocities than the measured velocity during the quiescent phase. Adding surges in the numerical model, by periodically increasing the sliding velocity, causes the glacier to retreat and oscillate around a smaller state when subject to the same mass-balance regime. Lowering the equilibrium line by 50 m lets the modeled surging glacier oscillate around a size similar to that of the present glacier, indicating that surging is an efficient long-term ablation mechanism.
Volume change of McCall Glacier, Arctic Alaska, USA, 1956–2003
Authors: Nolan Matt , Arendt Anthony , Rabus Bernhard , Hinzman Larry 
Published: November 2007

AbstractA long history of research documents that McCall Glacier, Arctic Alaska, USA, continues to lose mass at a rate that is likely increasing with time. We present a photo comparison (1958-2003) that visually documents these volume changes, along with survey measurements that quantify these losses. Measurements of longitudinal profiles initially acquired from airborne laser altimetry, and repeated by ground-based surveys, indicate that the areally averaged rate of thinning increased between 1956-93 and 1993-2002, from 0.35 ± 0.07 m a-1 to 0.47 ± 0.03 m a-1, respectively; total volume loss was (8.3 × 107) ± (1.7 × 107) m3 and (2.7 × 107) ± (0.2 × 107) m3 (all in water equivalent) for these two time periods. These profiles also indicate that a 1 km stretch of the mid-ablation area is behaving differently from this trend, with a rate of thinning that is not changing with time. Lastly we present a comparison of several methods for calculating volume change and assess their relative errors.
Geochemical properties of the water–snow–ice complexes in the area of Shokalsky glacier, Novaya Zemlya, in relation to tabular ground-ice formation
Authors: Leibman M.O. , Arkhipov S.M. , Perednya D.D. , Savvichev A.S. , Vanshtein B.G. , Hubberten H.-W. 
Published: November 2007

AbstractTabular (massive) ground ice in periglacial areas of the Russian Arctic (Barents and Kara Sea coasts) is considered to be a remnant of past glacial epochs and is thus used as proof of the glacial extent. In this paper, we argue that the origin of these tabular ice bodies, which can be used as archives of specific climatic conditions and periglacial environments, is intra-sedimentary (migration/intrusion). The objective of this study is to establish geochemical benchmarks describing the ice formation from atmospheric moisture and compare them with geochemical data of tabular ground ice. Shokalsky glacier on Novaya Zemlya (NZ), on the east coast of the Barents Sea, was chosen as a possible moisture source for the formation of tabular ground ice at the key section ‘Shpindler’ on Yugorsky peninsula, on the south coast of the Kara Sea. Tabular ice in the Shpindler section was compared to the Shokalsky glacier ice in both isotope/geochemical and structural aspects. In general, the hydrochemical properties of glacier ice at NZ and ground ice from Shpindler are closely correlated, while stable-isotope, microelemental and microbiological properties are substantially different. It was concluded that glacier ice most likely participated in the formation of tabular ground ice, but only as a source of refrozen meltwater.
Breaching of an ice dam at Qorlortossup tasia, south Greenland
Authors: Mayer Christoph , Schuler Thomas V. 
Published: November 2007

AbstractIn July 2003 an ice-dammed lake was suddenly drained in an outburst flood at Qorlortorssup tasia in south Greenland, the site of a projected hydropower station. The lake developed during the first decades of the 20th century as a result of the recession of the ice cap in this area. It used to drain over a shallow rock spillway towards Sermeq kangigdleq, the adjacent outlet glacier to the north. In order to assess the hazard potential and the additional water contribution from the enlarged catchment, the glacial lake and its surroundings were investigated. Based on the analysis of available historical data, field investigations and model results, the history of lake generation and the sudden outbreak were reconstructed. With the lake formation the ice dam lost its connection to the ice cap. The flood was initiated after the ice surface became low enough for the lake water to overflow the glacier towards Qorlortorssup tasia basin, creating a gully through the glacier which drained approximately 55 × 106 m3 of water over a period of 8-10 days. Thanks to the stability of the dam and the downstream damping of the flood, there was no serious threat to a farm that is situated close to the planned power-station site. In the future, we expect much smaller floods, as a result of partial closure of the gully by ice movement or snowdrift in the winter. The new drainage pattern into Qorlortorssup tasia basin, however, will be a permanent situation. The amount of this new water contribution can only be roughly estimated since the exact size of the drainage basin is not well known.
The role of atmospheric circulation in the growth of sea-ice extent in marginal seas around the Arctic Ocean
Authors: Rikiishi Kunio , Ohtake Hideaki , Katagiri Yurika 
Published: November 2007

AbstractSatellite data of weekly sea-ice extent and monthly means of objectively analyzed upper-air observation for the years 1978–95 are analyzed in order to investigate the role of atmospheric circulation in the growth of sea-ice extent in five marginal seas around the Arctic Ocean. It has been found that in all the regions the sea ice advances when a cold wind blows from the land (or from the Arctic ice field) to the region, whereas it hardly advances (or it retreats) when a warm wind blows over the region. Whether the wind is favorable or unfavorable for sea-ice growth depends on the position and intensity of the Icelandic low in the Atlantic sector and of the Aleutian low in the Pacific sector. This leads to a negative correlation in ice growth between the western region (Labrador or Okhotsk Sea) and the eastern region (Barents or Bering Sea). Significant correlations are also found across the continents, that is, positive correlations between the Barents Sea and the Sea of Okhotsk, and between the Labrador and Bering Seas. These teleconnections of ice growth can be explained by taking into account an observed negative correlation between the activities of the Icelandic low and Aleutian low.
Mass-balance rates derived by mapping internal tephra layers in Mýrdalsjökull and Vatnajökull ice caps, Iceland
Authors: Brandt Ola , Björnsson Helgi , Gjessing Yngvar 
Published: November 2007

AbstractInternal tephra layers of known age have been detected by radio-echo soundings within the Mýrdalsjökull and Vatnajökull ice caps in Iceland. Assuming steady state, the estimated strain rates since these isochrones were deposited on the glacier surface have been used to calculate past average specific net balance rates in the accumulation zones along three flowlines on Mýrdalsjökull and one on Vatnajökull. For the period 1918-91 the specific mass-balance rate has been estimated to 4.5 and 3.5 m a-1 at 1350 ma.s.l. on the southern and northern slopes of Mýrdalsjökull, respectively. At 1800 m elevation on the Bardarbunga ice dome in Vatnajökull, the specific net balance averaged over the last three centuries is estimated to be about 2.1 ma–1. Given this specific net balance, a revised age-depth timescale is presented for a 400 m deep ice core recovered in 1972 from Bardarbunga. The ice at the bottom is estimated to be from AD 1750.
Static mass-balance sensitivity of Arctic glaciers and ice caps using a degree-day approach
Authors: Woul Mattias De , Hock Regine 
Published: November 2007

AbstractFuture climate warming is predicted to be more pronounced in the Arctic where approximately two-thirds of all small glaciers on Earth are located. A simple mass-balance model was applied to 42 glaciers and ice caps north of 60° N to estimate mass-balance sensitivities to a hypothetical climate perturbation. The model is based on daily temperature and precipitation data from climate stations in the vicinity of each glacier and ice cap. A regression analysis was made using a degree-day approach where the annual sum of positive daily air temperatures was correlated to measured summer mass balance, and the total annual snow precipitation was correlated to measured winter mass balance. The net mass-balance sensitivity to a hypothetical temperature increase of +1 K ranged from -0.2 to -2.0 m a-1, and an assumed increase in precipitation of +10% changed the mass balance by <+0.1 to +0.4 m a-1, thus on average offsetting the effect of a temperature increase by approximately 20%. Maritime glaciers showed considerably higher mass-balance sensitivities than continental glaciers, in agreement with similar previous studies. The highest sensitivities were found in Iceland, exceeding those reported in previous studies. Extrapolating our results, glaciers and ice caps north of 60° N are estimated to contribute ∼0.6 mm a–1 K–1 to global sea-level rise. Our results highlight the value of long-term mass-balance records and meteorological records in remote areas.
The International Trans-Antarctic Scientific Expedition (ITASE): an overview
Authors: Mayewski Paul Andrew , Frezzotti Massimo , Bertler Nancy , Ommen Tas VAN , Hamilton Gordon , Jacka Tim H. , Welch Brian , Frey Markus , Dahe Qin , Jiawen Ren , Simões Jefferson , Fily Michel , Oerter Hans , Nishio Fumihiko , Isaksson Elisabeth , Mulvaney Robert , Holmund Per , Lipenkov Volodya , Goodwin Ian 
Published: November 2007

AbstractFrom its original formulation in 1990 the International Trans-Antarctic Scientific Expedition (ITASE) has had as its primary aim the collection and interpretation of a continent-wide array of environmental parameters assembled through the coordinated efforts of scientists from several nations. ITASE offers the ground-based opportunities of traditional-style traverse travel coupled with the modern technology of GPS, crevasse detecting radar, satellite communications and multidisciplinary research. By operating predominantly in the mode of an oversnow traverse, ITASE offers scientists the opportunity to experience the dynamic range of the Antarctic environment. ITASE also offers an important interactive venue for research similar to that afforded by oceanographic research vessels and large polar field camps, without the cost of the former or the lack of mobility of the latter. More importantly, the combination of disciplines represented by ITASE provides a unique, multidimensional (space and time) view of the ice sheet and its history. ITASE has now collected >20 000km of snow radar, recovered more than 240 firn/ice cores (total length 7000 m), remotely penetrated to ~4000m into the ice sheet, and sampled the atmosphere to heights of >20 km.
Solar forcing recorded by aerosol concentrations in coastal
Authors: Bertler Nancy A.N. , Mayewski Paul A. , Sneed Sharon B. , Naish Tim R. , Morgenstern Uwe , Barrett Peter J. 
Published: November 2007

AbstractIce-core chemistry data from Victoria Lower Glacier, Antarctica, suggest, at least for the last 50 years, a direct influence of solar activity variations on the McMurdo Dry Valleys (MDV) climate system via controls on air-mass input from two competing environments: the East Antarctic ice sheet and the Ross Sea. During periods of increased solar activity, when total solar irradiance is relatively high, the MDV climate system appears to be dominated by air masses originating from the Ross Sea, leading to higher aerosol deposition. During reduced solar activity, the Antarctic interior seems to be the dominant air-mass source, leading to lower aerosol concentration in the ice-core record. We propose that the sensitivity of the MDV to variations in solar irradiance is caused by strong albedo differences between the ice-free MDV and the ice sheet.
Sources and transport pathways of marine aerosol species into West Antarctica
Authors: Kaspari S. , Dixon D.A. , Sneed S.B. , Handley M.J. 
Published: November 2007

AbstractSixteen high-resolution marine aerosol (Na+, SO42–) records from spatially distributed International Trans-Antarctic Scientific Expedition (ITASE) ice cores spanning the last ~200 years from the Pine Island–Thwaites and Ross drainage systems and the South Pole are used to examine sources (sea spray and frost flowers) and transport pathways of marine aerosols into West Antarctica. Factors contributing to the amount of marine aerosols transported inland include sea-ice extent, the presence of open-water features (polynyas, leads), wind strength and direction, and the strength and positioning of low-pressure systems. Analysis of SO42–/Na+ ratios indicates that frost flowers can contribute significantly (40%) to the Na+ budget of Antarctic ice cores. Higher Na+ concentrations in the Ross drainage system may result from greater production of marine aerosols related to frost flowers in the Ross Sea region in association with greater sea-ice extent and larger open-water areas. Significant positive correlations of sea-ice extent and the Na+ time series exist in some regions of West Antarctica. Higher wind speeds in winter and higher Na+ concentrations when sea-level pressure is lower indicate that intensified atmospheric circulation enhances transport and production of marine aerosols.
A time marker at 17.5 kyr BP detected throughout West Antarctica
Authors: Jacobel Robert W. , Welch Brian C. 
Published: November 2007

AbstractDeep radar soundings as part of the International Trans-Antarctic Scientific Expedition (US-ITASE) traverses in West Antarctica have revealed a bright internal reflector that we have imaged throughout widespread locations across the ice sheet. The layer is seen in traverses emanating from Byrd Station in four directions and has been traced continuously for distances of 535km toward the Weddell Sea drainage, 500km toward South Pole, 150km toward the Executive Committee Range and 160km toward Kamb Ice Stream (former Ice Stream C). The approximate area encompassed by the layer identified in these studies is 250 000km2. If the layer identification can also be extended to Siple Dome where we have additional radar soundings (Jacobel and others, 2000), the approximate area covered would increase by 50%. In many locations echo strength from the layer rivals the bed echo in amplitude even though it generally lies at a depth greater than half the ice thickness. At Byrd Station, where the layer depth is 1260 m, an age of ~17.5 kyr BP has been assigned based on the Blunier and Brook (2001) chronology. Hammer and others (1997) note that the acidity at this depth is >20 times the amplitude of any other part of the core. The depiction of this strong and widespread dated isochrone provides a unique time marker for much of the ice in West Antarctica. We apply a layer-tracing technique to infer the depth–time scale at the inland West Antarctic ice sheet divide and use this in a simple model to estimate the average accumulation rate.