bluuebunny/crossref_metadata_2025_split huggingface dataset:
Self-similarity in glacier surface characteristics
Authors: Arnold Neil S. , Rees W. Gareth 
Published: November 2007

AbstractCatchment-wide information on glacier snow-cover depth, surface albedo and surface roughness is important input data for distributed models of glacier energy balance. In this study, we investigate the small-scale (mm to 100 m) spatial variability in these properties, with a view to better simulating this variability in such models. Data were collected on midre Lovénbreen, a 6 km2 valley glacier in northwest Svalbard. The spatial variability of all three properties was found to be self-similar over the range of scales under investigation. Snow depth and albedo exhibit a correlation length within which measurements were spatially autocorrelated. Late-winter and summer properties of snow depth differed, with smaller depths in summer due to melt, and shorter correlation lengths. Similar correlation lengths for snow depth and surface albedo may suggest that snow-depth variation is an important control on the small-scale spatial variability of glacier surface albedo. For surface roughness, the data highlight a possible problem in energy-balance studies which use microtopographic surveys to calculate aerodynamic roughness, in that the scale of the measurements made affects the calculated roughness value. This suggests that further investigations of the relationships between surface form and aerodynamic roughness of glacier surfaces are needed.
New velocity map and mass-balance estimate of Mertz Glacier, East Antarctica, derived from Landsat sequential imagery
Authors: Berthier Etienne , Raup Bruce , Scambos Ted 
Published: November 2007

AbstractAutomatic feature tracking on two Landsat images (acquired inJanuary 2000 and December 2001) generates a complete and accurate velocity field of Mertz Glacier, East Antarctica. This velocity field shows two main tributaries to the ice stream. Between the tributaries, a likely obstruction feature in the bedrock results in a slow-down of the flow. A third Landsat image, acquired in 1989 and combined with the 2000 image, permits the determination of the glacier mean velocity during the 1990s. Although some parts of the Mertz Glacier system show evidence of slight speed increase, we conclude that the Mertz flow speed is constant within our uncertainty (35 m a−1). Using this complete velocity field, new estimates of the ice discharge flux, 17.8 km3 a−1 (16.4 Gt a−1), and of the basal melting of the tongue, 11 m a−1 of ice, are given. Our results lead to an apparent imbalance of the drainage basin (ice discharge 3.5 km3 a−1 lower than the accumulation). Considering previous studies in the Mertz Glacier area, we then discuss the uncertainty of this imbalance and the problems with accumulation mapping for this region.
Temporal and spatial variation of the surface albedo of Morteratschgletscher, Switzerland, as derived from 12 Landsat images
Authors: (Lisette) Klok E. J. , Greuell Wouter , Oerlemans Johannes 
Published: November 2007

AbstractThis investigation uses Landsat images from 12 days in 1999 and 2000 to study the spatial and temporal variation in surface albedo of a glacier with a rugged topography: Morteratschgletscher, Switzerland. Our retrieval method considers all processes that substantially influence the relationship between the satellite signal and the surface albedo. The correction for the anisotropy of the reflected radiation field of ice and snow ranges up to 0.10, depending on wavelength band, solar zenith angle and surface type. We analyzed the uncertainties in the retrieval method and mainly expect errors in satellite-derived albedos for areas with large variation in topography and high albedos. The latter is due to application of bidirectional reflectance distribution function (BRDF) parameterizations for the anisotropic correction to albedos outside the parameterizations’ validity. On average, satellite-derived albedos exceed the measured surface albedo by 0.03. The glacier tongue is characterized by bands of low and high albedo, relating to ice with higher and lower concentrations of debris. The ice albedo shows no dependence on altitude, except at 2000–2200 m a.s.l. It increases during summer, which is likely associated with rainfall, as concluded from a comparison between summer rainfall and measured albedos.
Subglacial environment inferred from bedrock-coating siltskins, Mendenhall Glacier, Alaska, U.S.A.
Authors: Carter Carissa L. , Dethier David P. , Newton Robert L. 
Published: November 2007

AbstractRetreat of Mendenhall Glacier nearJuneau, Alaska, U.S.A., has exposed a bedrock ridge spotted with “siltskins”, patchy coatings of calcite-cemented clay-to sandsized lithic grains. Coatings 0.5–20 mm thick occur in two distinct morphologies. Thin, striated siltskins coat mainly stoss faces. Thicker, corrugated siltskins on lee faces consist of parallel micro-ridges elongated downslope. Thin-section analysis shows that siltskins consist of a basal, calcite-rich layer overlain by microlaminated layers of calcite-cemented lithic grains. Scanning electron microscope (SEM) energy-dispersive spectrometer (EDS) analysis of laminae and surfaces shows laterally persistent Ca/Si differences. Isotopic values for δO18 and δO13 ranged from −19.52‰ to −12.74‰ and −6.18‰ to −3.44‰, respectively, consistent with deposition from subglacial waters of varying isotopic composition and with derivation of carbon from inorganic sources. Corrugated siltskins are complex depositional features modified by erosional processes. Parallel micro-ridges spaced 1–10 mm apparently formed as sediment-rich water dripped down lee-slope rock faces. Ice–rock separation, flow energy and the transported sediment controlled the layering and depositional forms. Siltskins probably formed when a subglacial cavity system was active on the rock ridge and provide clues about how microscale hydrologic processes interact with larger-scale subglacial systems.
A two-dimensional shallow ice-flow model of Glacier de Saint-Sorlin, France
Authors: Meur Emmanuel Le , Vincent Christian 
Published: November 2007

AbstractA two-dimensional ice-flow model based on the shallow-ice approximation (SIA) is used to investigate the dynamics of Glacier de Saint-Sorlin, France. This glacier is well suited for this kind of study. First, the particular geometry of the glacier itself as well as that of the bedrock surface allows for correct applicability of the SIA (zeroth-order equations), provided that thickness changes and termini positions rather than short-scale dynamics are considered. Secondly, the wealth of available data for the glacier including mass-balance series and records of glacier changes provides a reliable forcing and a powerful constraining set for the model. Steady-state simulations show realistic results and the capabilities of the model in reproducing the glacier extent at the beginning of the 20th century. An extensive parameter study of ice rheology and sliding intensity is also carried out and the results are checked against the thickness changes as well as the glacier termini positions since 1905. It is possible to find a parameter combination that best matches these two types of data with an ice-flow rate factor of 2 × 10−24 Pa−3 s−1 and a Weertman-type sliding factor of 5 × 10−14 m8 N−3 a−1 which both appear to be in agreement with similar inferences from recent modelling attempts.
Energy exchange processes in the marginal ice zone of the Barents Sea, Arctic Ocean, during spring 1999
Authors: Ivanov Boris V. , Gerland Sebastian , Winther Jan-Gunnar , Goodwin Harvey 
Published: November 2007

AbstractWe present some new results describing energy exchange processes of drifting sea ice in the marginal ice zone (MIZ) in the Barents Sea, Arctic Ocean. All measurements and observations of meteorological parameters and ice conditions were taken on board the Norwegian research vessel Lance from 3 to 22 May 1999. Components of surface heat balance were measured and correlated with ice conditions and synoptic observations. These results can be used in atmospheric boundary layer modelling as lower boundary conditions. A relationship was found between modelled turbulent heat fluxes and observed sea-ice concentrations.
Glaciological response to distal tephra fallout from the 1947 eruption of Hekla, south Iceland
Authors: Kirkbride Martin P. , Dugmore Andrew J. 
Published: November 2007

AbstractGlacier responses to tephra deposition are shown to be highly variable where wind-transported eruption plumes produce narrow distal fallout zones with steep lateral thickness gradients. Significant but short-lived advances of faster-flowing glaciers can be triggered by deposition from modest eruptions. The 1947 eruption of Hekla, south Iceland, covered nearby glaciers with variable thicknesses of tephra, causing dramatic spatial variations in ablation rate. Relative snow ablation increased by an estimated >80% at the eastern margin of Eyjafjallajökull, but decreased by >54% at the western margin. Relative ice ablation increased by only 4% in the east but decreased by >75% at the western margin, only 15 km distant. The effect on mass balance therefore depends on tephra distribution as well as on the nature of the glacier surface. On Gígjökull, retardation of ablationwas greatest at the terminus, associated with an anomalous advance of ≥328 m between 1947 and 1954. Other glaciers in the fallout zone show either no recognizable response, or accelerated retreat. Advances will be short-lived due to the rapid redistribution of supraglacial tephra in a maritime climate, and the potential for discriminating between volcanically and climatically forced advances in the glacio-geomorphological record is low. The long-term glaciological effect of volcanism is to create thin, low-albedo covers after reworking, which make conditions less favourable for glaciation.
Surge-related topographic change of the glacier Sortebræ, East Greenland, derived from synthetic aperture radar interferometry
Authors: Pritchard Hamish , Murray Tavi , Strozzi Tazio , Barr Stuart , Luckman Adrian 
Published: November 2007

AbstractA major surge of the glacier complex of Sortebræ, East Greenland, occurred between 1992 and 1995. The impact of this surge on the topography of Sortebræ was examined through the production of a pre-surge (1981) digital elevation model (DEM) from interpolated digital map data, and a post-surge DEM from differential synthetic aperture radar interferometry using European Remote-sensing Satellite (ERS) imagery. The combined vertical error is typically 30–40 m; however, downdraw of up to 270 m in the reservoir zone, and uplift of up to 145 m in the receiving zone were measured. The upper glacier reservoir area discharged in excess of 24.3 ± 9.5 km3volume over the surge, of which ∼12.5 km3was stored in the advanced lower glacier, the balance being lost, predominantly to calving.
On friction and surface cracking during sliding of ice on ice
Authors: Montagnat Maurine , Schulson Erland M. 
Published: November 2007

AbstractAs a complement to earlier measurements on the friction of both granular fresh-water ice and S2 columnar salt-water ice, new experiments were performed on the friction of S2 columnar fresh-water ice sliding against itself at low velocities (5 × 10−7 to 5 × 10−1 m s−1) and at −10°C, using the same double-shear device as was used earlier. The results showed that under a given set of experimental conditions the kinetic coefficient of friction of S2 fresh-water ice compares favorably with that of the other two variants.The experiments also revealed friction-induced surface cracks and recrystallized grains.These deformation features are explained, respectively, in terms of fracture mechanics and an earlier model of dynamic recrystallization in ice.
Variations of Glaciar Coronas, Pyrenees, Spain, during the 20th century
Authors: Chueca Javier , Julián Asunción , López Ignacio 
Published: November 2007

AbstractGlaciar Coronas is one of the small cirque glaciers located in the Maladeta Range, central Spanish Pyrenees. The ice extends from 3220 to 3065 m a.s.l. Using early and modern photographs and aerial photographs, we study the evolution of the glacier during the 20th century, with particular focus on evaluating the variations in area, ice thickness and the withdrawal of the ice front. This information is compared with some basic climatic data (quarterly and annual evolution of temperatures and precipitation) recorded in the nearby Seira observatory. The results show that ice wastage, clearly associated with the main regional climatic evolution, has been dominant during the 20th century at Glaciar Coronas, but the rate has varied and has not been continuous. Three periods have been detected: (1) 1920s–early 1960s: ice depletion period; (2) early 1960s–mid-1980s: stabilization of the deglaciation process; (3) mid-1980s–1998: marked ice depletion period. The study shows a decrease in area of Glaciar Coronas from 19 ha in 1928 to 2.4 ha in 1998. The decrease in length from 1928 to 1998 has been 325 m.
Thickness changes on Whillans Ice Stream and Ice Stream C, West Antarctica, derived from laser altimeter measurements
Authors: Spikes Vandy Blue , Csatho Beáta M. , Hamilton Gordon S. , Whillans Ian M. 
Published: November 2007

AbstractRepeat airborne laser altimeter measurements are used to derive surface elevation changes on parts of Whillans Ice Stream and Ice Stream C, West Antarctica. Elevation changes are converted to estimates of ice equivalent thickness change using local accumulation rates, surface snow densities and vertical bedrock motions. The surveyed portions of two major tributaries of Whillans Ice Stream are found to be thinning almost uniformly at an average rate of ∼1 m a−1. Ice Stream C has a complicated elevation-change pattern, but is generally thickening. These results are used to estimate the contribution of each surveyed region to the current rate of global sea-level rise.
Oxygen isotopes in glacier-river water, Austre Okstindbreen, Okstindan, Norway
Authors: Theakstone Wilfred H. 
Published: November 2007

AbstractThere is no discernible river discharge from Austre Okstindbreen, Norway, in winter; any water formed by basal melting is likely to be stored in isolated cavities or sediments at the bed. In summer, a baseflow component of discharge, relatively depleted of 18O, is diluted by water more enriched in 18O. Glacier ice meltwater with a high δ18O value passes rapidly through channelized systems, and emerges in the glacier river within a few hours. Headward extension of the systems in late summer may tap water stored within the glacier since the previous summer’s close-down. Stored water also is released during early melt-season events, when the low-capacity drainage systems cannot accommodate inputs. The high δ18O value indicates that the probable source of the released water is glacier ice or low-altitude snowfall. Stratigraphic variations of δ18O values, resulting from changing weather conditions, characterize the accumulating winter snowpack. During the melt season, the mean δ18O value of the residual pack rises. The water leaving it, depleted of 18O, passes slowly through the glacier, smoothing out variations of supply. δ18O values of rain vary between and within events, and their effect on glacier-river δ18O values is unpredictable.
Tropical glacier meltwater contribution to stream discharge: a case study in the Cordillera Blanca, Peru
Authors: Mark Bryan G. , Seltzer Geoffrey O. 
Published: November 2007

AbstractDischarge measurements, climate observations and hydrochemical samples gathered monthly (1998/99) in the Yanamarey and Uruashraju glacier-fed catchments of the Cordillera Blanca, Peru, permit an analysis of the glacier meltwater contribution to stream-flow. These glacier catchments feed the Río Santa, which discharges into the Pacific Ocean. Based on a water-balance computation, glacier melt contributes an estimated 35% of the average discharge from the catchments. For comparison, a volumetric end-member mixing model of oxygen isotopes shows glacier melt contributes 30–45% to the total annual discharge. Based on stream geochemistry, discharge from the Yanamarey glacier catchment provides 30% of the annual volume discharged from the Querococha watershed, which is <10% glacierized. By analogy, the larger Río Santa watershed, also <10% glacierized, receives at least 12% of its annual discharge from melting glacier ice. Tributary watersheds to the Río Santa with larger fractions of glacier cover have less variable runoff and enhanced discharge, demonstrating that the glaciers effectively buffer stream discharge seasonally. With continued glacier melting, stream-flow will likely become more variable, and there will be less dry-season runoff.
Investigation of surface melting and dynamic thinning on Jakobshavn Isbræ, Greenland
Authors: Thomas Robert H. , Abdalati Waleed , Frederick Earl , Krabill William B. , Manizade Serdar , Steffen Konrad 
Published: November 2007

AbstractJakobshavn Isbræ is the most active glacier in Greenland, with an annual discharge of about 30 km3 of ice, and it is one of the few recently surveyed glaciers to thicken between 1993 and 1998, despite locally warm summers. Repeated airborne laser-altimeter surveys along a 120 km profile in the glacier basin show slow, sporadic thickening between 1991 and 1997, suggesting a small positive mass balance, but since 1997 there has been sustained thinning of several m a−1 within 20 km of the ice front, with lower rates of thinning further inland. Here, we use weather-station data from the coast and the ice sheet to estimate the effects on surface elevation of interannual variability in snowfall and surface melt rates, and thus to infer the temporal and spatial patterns of dynamic thinning. These show the glacier to have been close to balance before 1997 followed by a sudden transition to rapid thinning, initially confined to the lower reaches of the glacier (below about 500 m elevation), but progressively spreading inland until, between 1999 and 2001, thinning predominated over the entire surveyed region, up to 2000 m elevation. If this continues, the glacier calving front and probably its grounding line will retreat substantially in the very near future.
SEM/EDS observations of impurities in polar ice: artifacts or not?
Authors: Baker Ian , Cullen Daniel 
Published: November 2007

AbstractA series of experiments was undertaken to determine the origin of filaments found in grain boundaries and impurity spots found in grain interiors of polar ice during observation in the scanning electron microscope. It is shown that although the filaments are artifacts, they demonstrate the presence of impurities segregated to the grain boundary planes. It is also demonstrated that the impurities observed in the grain interior reside there and were not transported from the grain boundaries during specimen preparation or observation.
Accuracy of three-dimensional glacier surface velocities derived from radar interferometry and ice-sounding radar measurements
Authors: Mohr Johan Jacob , Reeh Niels , Madsen Søren Nørvang 
Published: November 2007

AbstractWe present a method for analyzing the errors involved in measuring three-dimensional glacier velocities with interferometric radar. We address the surface-parallel flow assumption and an augmented approach with a flux-divergence (FD) term. The errors in an interferometric ERS-1/-2 satellite radar dataset with ascending- and descending-orbit data covering Storstrømmen glacier, northeast Greenland, are assessed. The FD error assessment is carried out on airborne 60 MHz ice-sounding radar data from the same area. A simple model of an interferometric radar system is developed and analyzed. The error sources considered include phase noise, atmospheric distortions, baseline calibration errors, a dry snow layer, and the stationary-flow assumption used in differential interferometry. The additional error sources in the analysis of FD errors are noise, bias and unknown variations of the ice thickness, and approximations of the ice-flow model. The example glacier is now building up following a surge. The analysis shows that in the case study presented the errors are small enough to justify the use of both the estimated surface-parallel flow term of the vertical velocity and the estimated FD term of the vertical velocity.
Initial investigations of dynamics of the maritime Koryto glacier, Kamchatka, Russia
Authors: Yamaguchi Satoru , Naruse Renji , Sugiyama Shin , Matsumoto Takane , Murav’yev Yaroslav D. 
Published: November 2007

AbstractIce-flow velocities were measured at Koryto glacier on Kamchatka Peninsula, Russia, during a 37 day period in the middle of the 2000 melt season. Six survey points from the upper to the lower reaches of the glacier exhibited daily fluctuations in surface horizontal speed with major peaks that appeared at all points.We argue that basal motion is the major cause of flow on Koryto glacier. Downward vertical velocities measured over most of the glacier during the survey period are likely due to shrinking of englacial and subglacial cavities. This result may imply that a large amount of water is deposited in the early summer. Since 1960, Koryto glacier has retreated by 450 m and this retreat has accelerated following a decrease in winter precipitation after the mid 1970s.The glacier has thinned by 10–50 m during the last 40 years.
Three-dimensional surface velocities of Storstrømmen glacier, Greenland, derived from radar interferometry and ice-sounding radar measurements
Authors: Reeh Niels , Mohr Johan Jacob , Madsen Søren Nørvang , Oerter Hans , Gundestrup Niels S. 
Published: November 2007

AbstractNon-steady-state vertical velocities of up to 5 m a−1exceed the vertical surface-parallel flow (SPF) components over much of the ablation area of Storstrømmen, a large outlet glacier from the East Greenland ice sheet. Neglecting a contribution to the vertical velocity of this magnitude results in substantial errors (up to 20%) also on the south–north component of horizontal velocities derived by satellite synthetic aperture radar interferometry (InSAR) measurements. In many glacier environments, the steady-state vertical velocity component required to balance the annual ablation rate is 5–10 m a−1or more. This indicates that the SPF assumption may be problematic also for glaciers in steady state. Here we derive the three-dimensional surface velocity distribution of Storstrømmen by using the principle of mass conservation (MC) to combine InSAR measurements from ascending and descending satellite tracks with airborne ice-sounding radar measurement of ice thickness. The results are compared to InSAR velocities previously derived by using the SPF assumption, and to velocities obtained by in situ global positioning system (GPS) measurements. The velocities derived by using the MC principle are in better agreement with the GPS velocities than the previously calculated velocities derived with the SPF assumption.