scholarly journals A Re-Assessment of the Mass Balance of the Lambert Glacier Drainage Basin, Antarctica

1985 ◽  
Vol 31 (107) ◽  
pp. 34-38 ◽  
Author(s):  
N. F. McIntyre
Keyword(s):  
Mass Balance ◽  
Drainage Basin ◽  
Landsat Imagery ◽  
Accumulation Rates ◽  
Positive Mass ◽  
Recent Calculation ◽  
Ice Surface ◽  
Low Mass ◽  
Definition Of ◽  
Lambert Glacier

AbstractRe-definition of the interior drainage basin Lambert Glacier, using the most recent sources of ice-surface elevations, has shown its area to be 902000 km2, that is, 17% less than previous estimates. Landsat imagery of the steepest sloping part of the basin shows there is bare ice over an area of 56000 km2. Other evidence also indicates exceptionally low mass inputs and the distribution of accumulation rates has been up-dated. The result is a positive mass balance for the interior basin (+2 Gt a–1) and error limits which fall below zero. This is 47% less than the most recent calculation and illustrates the difficulty in deriving mass budgets in regions where data are scarce.

scholarly journals A Re-Assessment of the Mass Balance of the Lambert Glacier Drainage Basin, Antarctica

1985 ◽  
Vol 31 (107) ◽  
pp. 34-38 ◽  
Author(s):  
N. F. McIntyre
Keyword(s):  
Mass Balance ◽  
Drainage Basin ◽  
Landsat Imagery ◽  
Accumulation Rates ◽  
Positive Mass ◽  
Recent Calculation ◽  
Ice Surface ◽  
Low Mass ◽  
Definition Of ◽  
Lambert Glacier

AbstractRe-definition of the interior drainage basin Lambert Glacier, using the most recent sources of ice-surface elevations, has shown its area to be 902000 km2, that is, 17% less than previous estimates. Landsat imagery of the steepest sloping part of the basin shows there is bare ice over an area of 56000 km2. Other evidence also indicates exceptionally low mass inputs and the distribution of accumulation rates has been up-dated. The result is a positive mass balance for the interior basin (+2 Gt a–1 ) and error limits which fall below zero. This is 47% less than the most recent calculation and illustrates the difficulty in deriving mass budgets in regions where data are scarce.

scholarly journals The Dynamics of Austfonna, Nordaustlandet, Svalbard: Surface Velocities, Mass Balance, and Subglacial Melt Water

1989 ◽  
Vol 12 ◽  
pp. 37-45 ◽  
Author(s):  
Julian A. Dowdeswell ◽  
David J. Drewry
Keyword(s):  
Strain Rate ◽  
Mass Balance ◽  
Sea Level ◽  
Drainage Basin ◽  
Landsat Imagery ◽  
Lower Boundary ◽  
Surface Velocity ◽  
Ice Cap ◽  
Ice Surface ◽  
Melt Water

Glaciological measurements from Austfonna on Nordaustlandet, Svalbard, are needed as a prerequisite to mathematical modelling of ice-mass dynamics. Several upper and lower boundary conditions are set out in detail for a 670 km2 drainage basin (Basin 5) and are generalized to the whole ice cap where possible. The ice surface and bed topography are mapped for Basin 5. 30% of the basin lies below sea-level. Bed elevations range from -100 m to over 300 m, and maximum ice thickness is >500 m. A 21 km long trilateral network of stakes provides velocity and strain-rate data. Maximum ice-surface velocity is 47 m a−1 and maximum strain-rate is 0.64 × 10−2 a−1. Snow-line migration with time is mapped from digital Landsat MSS data, and mass-balance estimates are used to calculate balance velocities. At the equilibrium line, about 300–350 m in elevation, balance velocity and observed ice-surface velocity are comparable, indicating that the basin is approximately in balance. A first approximation is given for the rate of iceberg calving from the tide-water basin margins. Enhanced Landsat imagery also shows that turbid melt-water plumes of subglacial origin flow from the terminal ice cliffs, indicating that at least parts of the ice-cap margin are at the melting point. The margins of Basin 5, grounded below present sea-level, are likely to be underlain by deformable sediments, but inland the nature of the substrate is unknown.

scholarly journals The Dynamics of Austfonna, Nordaustlandet, Svalbard: Surface Velocities, Mass Balance, and Subglacial Melt Water

1989 ◽  
Vol 12 ◽  
pp. 37-45 ◽  
Author(s):  
Julian A. Dowdeswell ◽  
David J. Drewry
Keyword(s):  
Strain Rate ◽  
Mass Balance ◽  
Sea Level ◽  
Drainage Basin ◽  
Landsat Imagery ◽  
Lower Boundary ◽  
Surface Velocity ◽  
Ice Cap ◽  
Ice Surface ◽  
Melt Water

Glaciological measurements from Austfonna on Nordaustlandet, Svalbard, are needed as a prerequisite to mathematical modelling of ice-mass dynamics. Several upper and lower boundary conditions are set out in detail for a 670 km2drainage basin (Basin 5) and are generalized to the whole ice cap where possible. The ice surface and bed topography are mapped for Basin 5. 30% of the basin lies below sea-level. Bed elevations range from -100 m to over 300 m, and maximum ice thickness is >500 m. A 21 km long trilateral network of stakes provides velocity and strain-rate data. Maximum ice-surface velocity is 47 m a−1and maximum strain-rate is 0.64 × 10−2a−1. Snow-line migration with time is mapped from digital Landsat MSS data, and mass-balance estimates are used to calculate balance velocities. At the equilibrium line, about 300–350 m in elevation, balance velocity and observed ice-surface velocity are comparable, indicating that the basin is approximately in balance. A first approximation is given for the rate of iceberg calving from the tide-water basin margins. Enhanced Landsat imagery also shows that turbid melt-water plumes of subglacial origin flow from the terminal ice cliffs, indicating that at least parts of the ice-cap margin are at the melting point. The margins of Basin 5, grounded below present sea-level, are likely to be underlain by deformable sediments, but inland the nature of the substrate is unknown.

Recent changes of McCall Glacier, Alaska

1995 ◽  
Vol 21 ◽  
pp. 231-239 ◽  
Author(s):  
Bernhard Rabus ◽  
Keith Echelmeyer ◽  
Dennis Trabant ◽  
Carl Benson
Keyword(s):  
Climate Change ◽  
Exchange Rate ◽  
Mass Balance ◽  
Volume Loss ◽  
Average Mass ◽  
Ice Surface ◽  
Low Mass ◽  
The Mean ◽  
Alaskan Arctic ◽  
Drop Rate

Detailed surveys of McCall Glacier in the Alaskan Arctic reveal changes from 1972 to 1993. The ice surface dropped everywhere, by amounts ranging from about 3 m in the highest cirques tq more than 42 m near the present terminus. The total volume loss was 3.5+ 0.2 x 10' m(, resulting in an average mass balance of 0.33 + 0.01 in a . l he terminus has retreated by about 285 m at a rale of 12_.5 ma \ Results from photogrammetry for an earlier period, 1958-71, were I.16x 10'm3 and 0.13 ma for volume change and mass balance, respectively; the mean terminus retreat rate was then 5.7 m a . The changes have to be seen in the context of McCall Glacier’s low mass-exchange rate; annual accumulation and ablation, averaged over the years 1969 72 were only +0.16 and 0.3 m a '. Cross-profiles in the ablation area, surveyed at intervals of a few years, show an increased drop rate since the late 1970s. 7 he volume-ehange data suggest a climate warming in the early 1970s. Enhanced thinning of the lower ablation region and accelerated terminus retreat seem to lag this climate change by not more than 10 years, This indicates a reaction time of McCall Glacier that is considerably shorter than its theoretic response time of about 50 70 years.

scholarly journals Mass Balance of Four Cirque Glaciers in the Torngat Mountains of Northern Labrador, Canada

1986 ◽  
Vol 32 (111) ◽  
pp. 208-218
Author(s):  
Robert J. Rogerson
Keyword(s):  
Mass Balance ◽  
Temporal Pattern ◽  
Climatic Conditions ◽  
Spatial Variations ◽  
Equilibrium Line ◽  
Positive Mass ◽  
Negative Mass ◽  
Equilibrium Line Altitude ◽  
Ice Surface ◽  
Debris Cover

AbstractThe net mass balance of four small cirque glaciers (0.7–1.4 km2) in the Torngat Mountains of northern Labrador was measured for 1981–84, allowing three complete mass-balance years to be calculated. The two largest glaciers experienced positive mass-balance conditions in 1982 while all the glaciers were negative in 1983. The temporal pattern relates directly to general climatic conditions, in particular winter snowfall. Spatial variations of mass balance on the glaciers are the result of several factors including altitude, extent of supraglacial debris cover, slope, proximity to side and backwalls of the enclosing cirque, and the height of the backwall above the ice surface. Abraham Glacier, the smallest studied and with consistently the largest negative mass balance (–1.28 m in 1983), re-advanced an average of 1.2 m each year between 1981 and 1984. Mean equilibrium-line altitude (ELA) for the four glaciers is 1050 m, varying substantially from one glacier to another (+240 to –140 m) and from year to year (+60 to –30 m).

scholarly journals Regional Greenland accumulation variability from Operation IceBridge airborne accumulation radar

2017 ◽  
Vol 11 (2) ◽  
pp. 773-788 ◽  
Author(s):  
Gabriel Lewis ◽  
Erich Osterberg ◽  
Robert Hawley ◽  
Brian Whitmore ◽  
Hans Peter Marshall ◽  
...  
Keyword(s):  
Mass Balance ◽  
Sea Level Rise ◽  
Sea Level ◽  
Climate Models ◽  
Drainage Basin ◽  
Function Analysis ◽  
Greenland Ice Sheet ◽  
Snow Accumulation ◽  
Accumulation Rates ◽  
Surface Mass

Abstract. The mass balance of the Greenland Ice Sheet (GrIS) in a warming climate is of critical interest to scientists and the general public in the context of future sea-level rise. An improved understanding of temporal and spatial variability of snow accumulation will reduce uncertainties in GrIS mass balance models and improve projections of Greenland's contribution to sea-level rise, currently estimated at 0.089 ± 0.03 m by 2100. Here we analyze 25 NASA Operation IceBridge accumulation radar flights totaling  >  17 700 km from 2013 to 2014 to determine snow accumulation in the GrIS dry snow and percolation zones over the past 100–300 years. IceBridge accumulation rates are calculated and used to validate accumulation rates from three regional climate models. Averaged over all 25 flights, the RMS difference between the models and IceBridge accumulation is between 0.023 ± 0.019 and 0.043 ± 0.029 m w.e. a−1, although each model shows significantly larger differences from IceBridge accumulation on a regional basis. In the southeast region, for example, the Modèle Atmosphérique Régional (MARv3.5.2) overestimates by an average of 20.89 ± 6.75 % across the drainage basin. Our results indicate that these regional differences between model and IceBridge accumulation are large enough to significantly alter GrIS surface mass balance estimates. Empirical orthogonal function analysis suggests that the first two principal components account for 33 and 19 % of the variance, and correlate with the Atlantic Multidecadal Oscillation (AMO) and wintertime North Atlantic Oscillation (NAO), respectively. Regions that disagree strongest with climate models are those in which we have the fewest IceBridge data points, requiring additional in situ measurements to verify model uncertainties.

scholarly journals Changes in jökulhlaup sizes in Grímsvötn, Vatnajökull, Iceland, 1934-91, deduced from in-situ measurements of subglacial lake volume

1995 ◽  
Vol 41 (138) ◽  
pp. 263-272 ◽  
Author(s):  
Magnús T. Gudmundsson ◽  
Helgi Björnsson ◽  
Finnur Pálsson
Keyword(s):  
Mass Balance ◽  
Lake Level ◽  
Drainage Basin ◽  
Peak Discharge ◽  
Lake Area ◽  
Positive Mass ◽  
Ice Shelf ◽  
Subglacial Lake ◽  
Lake Volume ◽  
Cover Thickness

AbstractA record of volumes of jökulhlaups from the subglacial Grímsvötn lake, Vatnajökull, Iceland, has been derived for the period 1934–91. The change in lake volume during jökulhlaups is estimated from the lake area, ice-cover thickness and the drop in lake level. The jökulhlaup volumes have decreased gradually during this period of low volcanic activity and declining geothermal power. The two jökulhlaups in the 1930s each discharged about 4.5 km3(peak discharge 25-30 × 103m3s−1). In the 1980s, jökulhlaup volumes were 0.6.-1.2 km3(peak discharge 2 × 103m3s−1). The lake level required to trigger a jökulhlaup has risen as an ice dam east of the lake has thickened. Water flow in a jökulhlaup ceases when the base of a floating ice shelf covering Grímsvötn settles to about 1160 m a.s.l. Apparently, the jökulhlaups are cut off when the base of the ice shelf collapses on to a subglacial ridge bordering the lake on its eastern side. The decline in melting rates has resulted in a positive mass balance of the 160-170 km2Grímsvötn ice-drainage basin. Comparison of maps shows that the average positive mass-balance rate was 0.12 km3a−1(25% of the total accumulation) in the period 1946-87. A gradually increasing positive mass balance has prevailed since 1954, reaching 0.23 km3a−1in 1976-86 (48% of total accumulation).

scholarly journals Mass Balance of Four Cirque Glaciers in the Torngat Mountains of Northern Labrador, Canada

1986 ◽  
Vol 32 (111) ◽  
pp. 208-218 ◽  
Author(s):  
Robert J. Rogerson
Keyword(s):  
Mass Balance ◽  
Temporal Pattern ◽  
Climatic Conditions ◽  
Spatial Variations ◽  
Equilibrium Line ◽  
Positive Mass ◽  
Negative Mass ◽  
Equilibrium Line Altitude ◽  
Ice Surface ◽  
Debris Cover

Abstract The net mass balance of four small cirque glaciers (0.7–1.4 km2) in the Torngat Mountains of northern Labrador was measured for 1981–84, allowing three complete mass-balance years to be calculated. The two largest glaciers experienced positive mass-balance conditions in 1982 while all the glaciers were negative in 1983. The temporal pattern relates directly to general climatic conditions, in particular winter snowfall. Spatial variations of mass balance on the glaciers are the result of several factors including altitude, extent of supraglacial debris cover, slope, proximity to side and backwalls of the enclosing cirque, and the height of the backwall above the ice surface. Abraham Glacier, the smallest studied and with consistently the largest negative mass balance (–1.28 m in 1983), re-advanced an average of 1.2 m each year between 1981 and 1984. Mean equilibrium-line altitude (ELA) for the four glaciers is 1050 m, varying substantially from one glacier to another (+240 to –140 m) and from year to year (+60 to –30 m).

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