Recession, thinning, and slowdown of Greenland's Mittivakkat Gletscher

Abstract. Here, we document changes for the Mittivakkat Gletscher, the glacier in Greenland (disconnected to the Greenland Ice Sheet, GrIS) having the longest observed mass balance and surface velocity time series (since 1995). Between 1986 and 2011, this glacier decreased by 15% in mean ice thickness and 30% in volume. We attribute these changes to summer warming and less winter snowfall. The vertical strain was able to compensate about 60% of the elevation change due to surface mass balance (SMB) in the lower part, and about 25% in the upper part. The annual mean ice surface velocity decreased by 30%, likely as a dynamic effect of ice thinning. Mittivakkat Gletscher summer surface velocities were on average 50–60% above winter background values, and up to 160% higher during peak velocity events.

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Are longitudinal ice-surface structures on the Antarctic Ice Sheet indicators of long-term ice-flow configuration?

Earth Surface Dynamics Discussions ◽

10.5194/esurfd-2-911-2014 ◽

2014 ◽

Vol 2 (2) ◽

pp. 911-933 ◽

Cited By ~ 1

Author(s):

N. F. Glasser ◽

S. J. A. Jennings ◽

M. J. Hambrey ◽

B. Hubbard

Keyword(s):

Flow Line ◽

Ice Sheet ◽

Surface Structures ◽

Surface Velocity ◽

Ice Flow ◽

Antarctic Ice Sheet ◽

Ice Surface ◽

Ice Stream ◽

The Antarctic

Abstract. Continent-wide mapping of longitudinal ice-surface structures on the Antarctic Ice Sheet reveals that they originate in the interior of the ice sheet and are arranged in arborescent networks fed by multiple tributaries. Longitudinal ice-surface structures can be traced continuously down-ice for distances of up to 1200 km. They are co-located with fast-flowing glaciers and ice streams that are dominated by basal sliding rates above tens of m yr-1 and are strongly guided by subglacial topography. Longitudinal ice-surface structures dominate regions of converging flow, where ice flow is subject to non-coaxial strain and simple shear. Associating these structures with the AIS' surface velocity field reveals (i) ice residence times of ~ 2500 to 18 500 years, and (ii) undeformed flow-line sets for all major flow units analysed except the Kamb Ice Stream and the Institute and Möller Ice Stream areas. Although it is unclear how long it takes for these features to form and decay, we infer that the major ice-flow and ice-velocity configuration of the ice sheet may have remained largely unchanged for several thousand years, and possibly even since the end of the last glacial cycle. This conclusion has implications for our understanding of the long-term landscape evolution of Antarctica, including large-scale patterns of glacial erosion and deposition.

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Long-Term Glacier Variations Measured by Photogrammetry. A Re-Survey of Tunsbergdalsbreen after 24 Years

Journal of Glaciology ◽

10.3189/s002214300001902x ◽

1966 ◽

Vol 6 (43) ◽

pp. 3-18

Author(s):

W. Kick

Keyword(s):

Eastern Alps ◽

Ice Thickness ◽

Surface Level ◽

Ice Surface ◽

Geodetic Measurements ◽

Alpine Glaciers ◽

Transverse Profile

AbstractThe relations between geodetic measurements of the surface level variations Δh and net budget measurements by stakes arc discussed. In 1961, 24 yr. after Finsterwalder’s survey, Tunsbergdalsbreen, the largest and most regular of the 26 outlet glaciers of Jostedalsbreen, was re-surveyed. The variations in the length, area, ice thickness, and volume of its tongue are shown. The lake Brimkjelen was 99 m. deep in 1937; it disappeared in 1949. From 1900–40 the whole Jostedalsbre lost 0.4 m./yr., about the same amount as the glaciers of the eastern Alps. The ice thickness of the Tunsbergdalsbre tongue diminished by −ΔhA = 0.46+0.0022 (1500−A) m./yr. from 1937–61; for the eastern Alps from 1920–50 −ΔhA ≈ 0.53+0.0021 (2850−A) m./yr. where A is the altitude. The change of Δh with altitude is much the same. The amounts of the retreat of the Alpine glaciers, of Tunsbergdalshreen, and at Werenskioldbreen, Vestspitsbergen, were the greater the higher the latitude. The numerical relations between Δh, net budget, and ice movement are shown. The temporary velocity transverse profile of 1937 served as a prototype for the streaming mode of flow, but in 1961 the glacier partially showed Blockschollen movement, although the velocity had decreased by more than 30 per cent. The article is accompanied by a map showing ice surface contours in 1937 and 1961.

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Ice flux of Plogbreen, a small ice stream in Dronning Maud Land, Antarctica

Annals of Glaciology ◽

10.3189/172756404781813844 ◽

2004 ◽

Vol 39 ◽

pp. 409-416

Author(s):

Jim Hedfors ◽

Veijo Allan Pohjola

Keyword(s):

Mass Balance ◽

Ice Core ◽

Austral Summer ◽

Snow Accumulation ◽

Surface Velocity ◽

Cross Sectional ◽

Ice Surface ◽

Dronning Maud Land ◽

Using Data

AbstractAs part of a long-term mass-balance program run by SWEDARP since 1988, a detailed study on Plogbreen, Dronning Maud Land, Antarctica, was undertaken during the austral summer of 2003 to investigate the long-term mass balance. We compare ice outflux, φout, through a cross-sectional gate with ice influx, φin, from the upstream catchment area. The φin is based on calculations of snow accumulation upstream of the gate using data available from published ice-core records. The φout is based on Glen’s flow law aided by thermodynamic modeling and force-budget calculations. Input data from the field consist of measurements of ice surface velocity and ice geometry. The ice surface velocity was measured using repeated differential global positioning system surveying of 40 stakes over a period of 25 days. The ice geometry was determined by 174 km of ground-penetrating radar profiling using ground-based 8MHz dipole antennas. This study presents the collected velocity and geometry data as well as the calculated ice flux of Plogbreen. The results show a negatively balanced system within the uncertainty limits; φout = 0.55 ± 0.05 km3 a–1 and φin = 0.4 ± 0.1 km3 a–1. We speculate that the negative balance can be explained by recent eustatic increase reducing resistive stresses and inducing accelerated flow.

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Incorporation of Flow Stripes as Constraints for Calibrating Ice Surface Velocity Measurements from Interferometric SAR Data

Photogrammetric Engineering & Remote Sensing ◽

10.14358/pers.74.12.1501 ◽

2008 ◽

Vol 74 (12) ◽

pp. 1501-1508 ◽

Cited By ~ 2

Author(s):

Hongxing Liu ◽

Jaehyung Yu ◽

Zhiyuan Zhao ◽

Kenneth C. Jezek

Keyword(s):

Surface Velocity ◽

Velocity Measurements ◽

Ice Surface ◽

Sar Data ◽

Interferometric Sar

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Basal conditions of Kongsvegen at the onset of surge - revealed using seismic vibroseis surveys

10.5194/egusphere-egu2020-7185 ◽

2020 ◽

Author(s):

Emma C. Smith ◽

Anja Diez ◽

Olaf Eisen ◽

Coen Hofstede ◽

Jack Kohler

Keyword(s):

Surface Velocity ◽

Ablation Area ◽

Physical Conditions ◽

Ice Surface ◽

Undisturbed Sediment ◽

Glacier Surges ◽

Clear Change ◽

Electrodynamic Vibrator ◽

Term Monitoring

<p>Kongsvegen is a well-studied surge-type glacier in the Kongsfjord area of northwest Svalbard. Long-term monitoring has shown that the ice surface velocity has been increasing since around 2014; presenting a unique opportunity to study the internal ice structure, basal conditions and thermal regime, all of which play a crucial role in initiating glacier surges. In April 2019, three-component seismic vibroseis surveys were conducted at two sites on the glacier, using a small Electrodynamic Vibrator source (ElViS). The first site is in the ablation area and the second near the equilibrium line, where the greatest increase in ice-surface velocity has been observed.</p><p>Initial analysis indicates the conditions at the two sites are significantly different. At the ablation area site, the ice is around 220 m thick, and the bed is relatively flat and unvaried, with no clear change in the bed reflection along the profile. The bed appears to comprise a uniform and undisturbed sediment package ~60 m thick, and there are no clear englacial reflections within the ice column. By contrast at the second site, the ice is around 390 m thick, and the internal ice structure is much more complex. Clear internal ice reflections are visible at depths between 150-250 m, and further reflections in the 100 m above the bed indicate there could be shearing or sediment entrainment in this area. Below the bed, cross-cutting layers are clearly visible and the bed reflection itself shows changing reflection polarity &#8211; suggesting water or very wet sediment is present in some areas.&#160; The contrast between these two sites at the onset of a surge phase allows us to investigate the physical conditions that are conducive to surge initiation, both at the ice-bed interface and within the ice column.</p>

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Long-Term Glacier Variations Measured by Photogrammetry. A Re-Survey of Tunsbergdalsbreen after 24 Years

Journal of Glaciology ◽

10.1017/s002214300001902x ◽

1966 ◽

Vol 6 (43) ◽

pp. 3-18 ◽

Cited By ~ 9

Author(s):

W. Kick

Keyword(s):

Eastern Alps ◽

Ice Thickness ◽

Surface Level ◽

Ice Surface ◽

Geodetic Measurements ◽

Alpine Glaciers ◽

Transverse Profile

Abstract The relations between geodetic measurements of the surface level variations Δh and net budget measurements by stakes arc discussed. In 1961, 24 yr. after Finsterwalder’s survey, Tunsbergdalsbreen, the largest and most regular of the 26 outlet glaciers of Jostedalsbreen, was re-surveyed. The variations in the length, area, ice thickness, and volume of its tongue are shown. The lake Brimkjelen was 99 m. deep in 1937; it disappeared in 1949. From 1900–40 the whole Jostedalsbre lost 0.4 m./yr., about the same amount as the glaciers of the eastern Alps. The ice thickness of the Tunsbergdalsbre tongue diminished by −Δh A = 0.46+0.0022 (1500−A) m./yr. from 1937–61; for the eastern Alps from 1920–50 −Δh A ≈ 0.53+0.0021 (2850−A) m./yr. where A is the altitude. The change of Δh with altitude is much the same. The amounts of the retreat of the Alpine glaciers, of Tunsbergdalshreen, and at Werenskioldbreen, Vestspitsbergen, were the greater the higher the latitude. The numerical relations between Δh, net budget, and ice movement are shown. The temporary velocity transverse profile of 1937 served as a prototype for the streaming mode of flow, but in 1961 the glacier partially showed Blockschollen movement, although the velocity had decreased by more than 30 per cent. The article is accompanied by a map showing ice surface contours in 1937 and 1961.

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Five decades of shrinkage of July 1st glacier, Qilian Shan, China

Journal of Glaciology ◽

10.3189/172756506781828836 ◽

2006 ◽

Vol 52 (176) ◽

pp. 11-16 ◽

Cited By ~ 24

Author(s):

Akiko Sakai ◽

Koji Fujita ◽

Keqin Duan ◽

Jianchen Pu ◽

Masayoshi Nakawo ◽

...

Keyword(s):

Surface Melting ◽

Temperature Data ◽

Surface Elevation ◽

Surface Velocity ◽

Ice Thickness ◽

Glacier Shrinkage ◽

The Past ◽

Glacier Ice ◽

Elevation Changes ◽

Increasing Temperature

AbstractA survey of July 1st glacier, Qilian Shan, China, was carried out in 2002. Previously, the glacier’s boundary had been recorded in 1956, and further research had been carried out in the mid- 1970s and 1980s. Our survey reveals that area shrinkage and surface lowering have accelerated in the past 15 years. Surface elevation changes can result from changes in accumulation, surface melting and emergence velocity. The contributions of these elements to surface lowering are evaluated at the lower part of the glacier from observations of surface velocity, ice thickness and precipitation, and from temperature data near the glacier. Apart from the effect of glacier ice redistribution, our analysis reveals quantitatively that the recent accelerated glacier shrinkage has been caused by increasing temperature. Furthermore, it is established that meltwater discharge from the glacier in the past 17 years has increased due to glacier shrinkage, by about 50% over that from 1975 to 1985.

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The flow of a polythermal glacier: McCall Glacier, Alaska, U.S.A.

Journal of Glaciology ◽

10.1017/s0022143000035139 ◽

1997 ◽

Vol 43 (145) ◽

pp. 522-536 ◽

Cited By ~ 32

Author(s):

B.T. Rabus ◽

K. A. Echelmeyer

Keyword(s):

Surface Profile ◽

Surface Velocity ◽

Ice Thickness ◽

Longitudinal Stress ◽

Surface Slope ◽

Basal Sliding ◽

Speed Up ◽

Polythermal Glacier ◽

Long Term Variations

AbstractWe have analyzed the flow of polythermal McCall Glacier in Arctic Alaska. Using measurements of surface velocity from the 1970s and 1990s, together with measurements of ice thickness and surface slope, we have investigated both the present flow and seasonal and long-term flow variations. Our analysis of the present flow reveals that (i) longitudinal stress coupling is important along the entire length of the glacier, and (ii) there is significant basal sliding beneath a 2 km long section of the lower glacier. This sliding exists year-round and it accounts for more than 70% of the total motion there. We have developed a numerical model which shows that such a sliding anomaly causes an asymmetric decrease in ice thickness. Accompanying this decrease in thickness is a decrease in surface slope at the center of the anomaly and an increase in slope up-glacier from it. Both effects are reflected in the observed surface profile of McCall Glacier.The longitudinal stress-coupling length of McCall Glacier is three times the ice thickness, almost twice that typical of temperate glaciers. This is a direct effect of lower strain rates, which themselves are associated with the smaller mass-balance gradients of Arctic and continental glaciers. Long-term variations in surface velocity between the 1970s and 1990s are explained solely by the effects of changes in glacier geometry on the deformational flow contribution. This means that long-term variations in the spatial patterns of longitudinal stresses and basal sliding must have been small. Seasonally, Velocities reach their annual minimum in spring and increase during the short summer nick season by up to 75% above mean winter values. However, the extra motion associated with the period of elevated velocities is only about 5% of the total annual motion. The speed-up is due to an increase in basal sliding. This implies that most of the glacier bed is at the melting point. The zone a affected by the melt-season speed-up extends well up-glacier of any moulins or other obvious sources for melt water at the bed.

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The flow of a polythermal glacier: McCall Glacier, Alaska, U.S.A.

Journal of Glaciology ◽

10.3189/s0022143000035139 ◽

1997 ◽

Vol 43 (145) ◽

pp. 522-536 ◽

Cited By ~ 1

Author(s):

B.T. Rabus ◽

K. A. Echelmeyer

Keyword(s):

Surface Profile ◽

Surface Velocity ◽

Ice Thickness ◽

Longitudinal Stress ◽

Surface Slope ◽

Basal Sliding ◽

Speed Up ◽

Polythermal Glacier ◽

Long Term Variations

AbstractWe have analyzed the flow of polythermal McCall Glacier in Arctic Alaska. Using measurements of surface velocity from the 1970s and 1990s, together with measurements of ice thickness and surface slope, we have investigated both the present flow and seasonal and long-term flow variations. Our analysis of the present flow reveals that (i) longitudinal stress coupling is important along the entire length of the glacier, and (ii) there is significant basal sliding beneath a 2 km long section of the lower glacier. This sliding exists year-round and it accounts for more than 70% of the total motion there. We have developed a numerical model which shows that such a sliding anomaly causes an asymmetric decrease in ice thickness. Accompanying this decrease in thickness is a decrease in surface slope at the center of the anomaly and an increase in slope up-glacier from it. Both effects are reflected in the observed surface profile of McCall Glacier.The longitudinal stress-coupling length of McCall Glacier is three times the ice thickness, almost twice that typical of temperate glaciers. This is a direct effect of lower strain rates, which themselves are associated with the smaller mass-balance gradients of Arctic and continental glaciers. Long-term variations in surface velocity between the 1970s and 1990s are explained solely by the effects of changes in glacier geometry on the deformational flow contribution. This means that long-term variations in the spatial patterns of longitudinal stresses and basal sliding must have been small. Seasonally, Velocities reach their annual minimum in spring and increase during the short summer nick season by up to 75% above mean winter values. However, the extra motion associated with the period of elevated velocities is only about 5% of the total annual motion. The speed-up is due to an increase in basal sliding. This implies that most of the glacier bed is at the melting point. The zone a affected by the melt-season speed-up extends well up-glacier of any moulins or other obvious sources for melt water at the bed.

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