scholarly journals Subglacial Drainage Evolution Modulates Seasonal Ice Flow Variability of Three Tidewater Glaciers in Southwest Greenland

2020 ◽  
Vol 125 (9) ◽  
Author(s):  
B. J. Davison ◽  
A. J. Sole ◽  
T. R. Cowton ◽  
J. M. Lea ◽  
D. A. Slater ◽  
...  
Keyword(s):  
Ice Flow ◽  
Tidewater Glaciers ◽  
Flow Variability ◽  
Southwest Greenland ◽  
Subglacial Drainage

A 3D full-Stokes model of Store Glacier, Greenland, with coupling of ice flow, subglacial hydrology, submarine melting and calving

2020 ◽  
Author(s):  
Samuel Cook ◽  
Poul Christoffersen ◽  
Joe Todd ◽  
Donald Slater ◽  
Nolwenn Chauché ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Water Pressure ◽  
Drainage System ◽  
Greenland Ice Sheet ◽  
Pressure System ◽  
Ice Flow ◽  
Tidewater Glaciers ◽  
Iceberg Calving ◽  
Subglacial Drainage

<p>Tidewater glaciers are complex systems, which present numerous modelling challenges with regards to integrating a multitude of environmental processes spanning different timescales. At the same time, an accurate representation of these systems in models is critical to being able to effectively predict the evolution of the Greenland Ice Sheet and the resulting sea-level rise. In this study, we present results from numerical simulations of Store Glacier in West Greenland that couple ice flow modelled by Elmer/Ice with subglacial hydrology modelled by GlaDS and submarine melting represented with a simple plume model forced by hydrographic observations. The simulations capture the seasonal evolution of the subglacial drainage system and the glacier’s response, and also include the influence of plume-induced ice front melting on calving and buttressing from ice melange present in winter and spring.</p><p>Through running the model for a 6-year period from 2012 to 2017, covering both high- and low-melt years, we find inputs of surface meltwater to the subglacial system establishes channelised subglacial drainage with channels >1 m<sup>2</sup> extending 30-60 km inland depending on the amount of supraglacial runoff evacuated subglacially. The growth of channels is, however, not sufficiently fast to accommodate all inputs of meltwater from the surface, which means that basal water pressures are generally higher in warmer summers compared to cooler summers and lowest in winter months. As a result, the simulated flow of Store Glacier is such that velocities peak in warmer summers, though we suggest that higher surface melt levels may lead to sufficient channelisation for a widespread low-water-pressure system to evolve, which would reduce summer velocities. The results indicate that Greenland’s contribution to sea-level rise is sensitive to the evolution of the subglacial drainage system and especially the ability of channels to grow and accommodate surface meltwater effectively. We also posit that the pattern of plume melting encourages further calving by creating an indented calving front with ‘headlands’ that are laterally unsupported and therefore more vulnerable to collapse. We validate our simulations with a three-week record of iceberg calving events gathered using a terrestrial radar interferometer installed near the calving terminus of Store Glacier.</p>

Helheim Glacier's terminus position controls its seasonal and inter-annual ice flow variability

2021 ◽  
Author(s):  
Gong Cheng ◽  
Mathieu Morlighem ◽  
Jérémie Mouginot ◽  
Daniel Cheng
Keyword(s):  
Ice Flow ◽  
Flow Variability

scholarly journals Contrasts in the response of adjacent fjords and glaciers to ice-sheet surface melt in West Greenland

2016 ◽  
Vol 57 (73) ◽  
pp. 25-38 ◽  
Author(s):  
Timothy C. Bartholomaus ◽  
Leigh A. Stearns ◽  
David A. Sutherland ◽  
Emily L. Shroyer ◽  
Jonathan D. Nash ◽  
...  
Keyword(s):  
Satellite Remote Sensing ◽  
Heat Content ◽  
Flow Speed ◽  
High Temporal Resolution ◽  
Glacier Surface ◽  
Ice Flow ◽  
Tidewater Glaciers ◽  
Circulation Patterns ◽  
Key Factor ◽  
Surface Melt

ABSTRACTNeighboring tidewater glaciers often exhibit asynchronous dynamic behavior, despite relatively uniform regional atmospheric and oceanic forcings. This variability may be controlled by a combination of local factors, including glacier and fjord geometry, fjord heat content and circulation, and glacier surface melt. In order to characterize and understand contrasts in adjacent tidewater glacier and fjord dynamics, we made coincident ice-ocean-atmosphere observations at high temporal resolution (minutes to weeks) within a 10 000 km2 area near Uummannaq, Greenland. Water column velocity, temperature and salinity measurements reveal systematic differences in neighboring fjords that imply contrasting circulation patterns. The observed ocean velocity and hydrography, combined with numerical modeling, suggest that subglacial discharge plays a major role in setting fjord conditions. In addition, satellite remote sensing of seasonal ice flow speed and terminus position reveal both speedup and slow-down in response to melt, as well as differences in calving style among the neighboring glaciers. Glacier force budgets and modeling also point toward subglacial discharge as a key factor in glacier behavior. For the studied region, individual glacier and fjord geometry modulate subglacial discharge, which leads to contrasts in both fjord and glacier dynamics.

scholarly journals Mapping Glacier Forelands Based on UAV BVLOS Operation in Antarctica

2020 ◽  
Vol 12 (4) ◽  
pp. 630
Author(s):  
Maciej Dąbski ◽  
Anna Zmarz ◽  
Mirosław Rodzewicz ◽  
Małgorzata Korczak-Abshire ◽  
Izabela Karsznia ◽  
...  
Keyword(s):  
Ice Age ◽  
South Shetland Islands ◽  
Ground Moraine ◽  
King George Island ◽  
Ice Flow ◽  
Tidewater Glaciers ◽  
Geomorphological Mapping ◽  
Digital Elevation ◽  
Glacial Dynamics ◽  
Elevation Model

The aim of this article is to show geomorphological mapping of remote Antarctic locations using images taken by a fixed-wing unmanned aerial vehicle (UAV) during the Beyond Visual Line of Sight (BVLOS) operations. We mapped landform assemblages developed in forelands of Ecology Glacier (EGF), Sphinx Glacier (SGF) and Baranowski Glacier (BGF) in Antarctic Specially Protected Area No. 128 (ASPA 128) on King George Island (South Shetland Islands) and inferred about glacial dynamics. The orthophoto and digital elevation model allowed for geomorphological mapping of glacial forelands, including (i) glacial depositional landforms, (ii) fluvial and fluvioglacial landforms, (iii) littoral and lacustrine landforms, (iv) bodies of water, and (v) other. The largest area is occupied by ground moraine and glacial lagoons on EGF and BGF. The most profound features of EGF are the large latero-frontal moraine ridges from Little Ice Age and the first half of the 20th century. Large areas of ground moraine, frequently fluted and marked with large recessional moraine ridges, dominate on SGF. A significant percentage of bedrock outcrops and end moraine complexes characterize BGF. The landform assemblages are typical for discontinuous fast ice flow of tidewater glaciers over a deformable bed. It is inferred that ice flow velocity decreased as a result of recession from the sea coast, resulting in a significant decrease in the length of ice cliffs and decrease in calving rate. Image acquisition during the fixed-wing UAV BVLOS operation proved to be a very robust technique in harsh polar conditions of King George Island.

scholarly journals “Striations” Produced by Catastrophic Subglacial Drainage of a Glacier-dammed Lake, Mjølkedalsbreen, Southern Norway

1989 ◽  
Vol 35 (120) ◽  
pp. 193-196 ◽  
Author(s):  
Danny McCarroll ◽  
John A. Matthews ◽  
Richard A. Shakesby
Keyword(s):  
Control Site ◽  
Ice Flow ◽  
Length Width ◽  
Flow Directions ◽  
Dammed Lake ◽  
Width Measurements ◽  
Southern Norway ◽  
Subglacial Drainage

Abstract “Striations” produced by catastrophic subglacial drainage of an ice-dammed lake were investigated in front of Mjelkedalsbreen, Jotunheimen, southern Norway. At each site, length, width, and orientation of at least 50 “striations” were recorded. These data are compared with similar measurements from a glacially abraded “control” site. On the basis of length or width measurements alone, “striations” produced by subglacial drainage are not consistently distinguishable from those produced by glacial abrasion. However, the former display more variable orientations and cross-cutting relationships which could be misinterpreted as indicating changing ice-flow directions. They can be recognized by the occurrence of some “striations” with relatively low length : width ratios, which indicate the transport of boulders by saltation.

scholarly journals About this title ‐ Atlas of Submarine Glacial Landforms: Modern, Quaternary and Ancient

10.1144/m46 ◽  
2016 ◽  
Vol 46 (1) ◽  
pp. NP.1-NP ◽  
Keyword(s):  
High Latitude ◽  
Ice Flow ◽  
Tidewater Glaciers ◽  
Current State ◽  
Continental Shelves ◽  
Antarctic Waters ◽  
Sedimentary Architecture ◽  
Resolution Imaging ◽  
Submarine Landforms ◽  
Glacial Landforms

New geophysical techniques (multibeam echo sounding and 3D seismics) have revolutionized high-resolution imaging of the modern seafloor and palaeo-shelf surfaces in Arctic and Antarctic waters, generating vast quantities of data and novel insights into sedimentary architecture and past environmental conditions. The Atlas of Submarine Glacial Landforms is a comprehensive and timely summary of the current state of knowledge of these high-latitude glacier-influenced systems.The Atlas presents over 180 contributions describing, illustrating and discussing the full variability of landforms found on the high-latitude glacier-influenced seafloor, from fjords and continental shelves to the continental slope, rise and deep-sea basins beyond. The distribution and geometry of these submarine landforms provide key information on past ice-sheet extent and the direction and nature of ice flow and dynamics. The papers discuss individual seafloor landforms, landform assemblages and entire landsystems from relatively mild to extreme glacimarine climatic settings and on timescales from the modern margins of tidewater glaciers, through Quaternary examples to ancient glaciations in the Late Ordovician.

scholarly journals Subglacial drainage processes at a High Arctic polythermal valley glacier

2005 ◽  
Vol 51 (172) ◽  
pp. 15-24 ◽  
Author(s):  
Robert G. Bingham ◽  
Peter W. Nienow ◽  
Martin J. Sharp ◽  
Sarah Boon
Keyword(s):  
Drainage System ◽  
Structural Evolution ◽  
Subsequent Development ◽  
High Arctic ◽  
Breakthrough Curves ◽  
Ice Flow ◽  
Dye Tracer ◽  
Arctic Glacier ◽  
Tracer Experiments ◽  
Subglacial Drainage

AbstractDye-tracer experiments undertaken over two summer melt seasons at polythermal John Evans Glacier, Ellesmere Island, Canada, were designed to investigate the character of the subglacial drainage system and its evolution over a melt season. In both summers, dye injections were conducted at several moulins and traced to a single subglacial outflow. Tracer breakthrough curves suggest that supraglacial meltwater initially encounters a distributed subglacial drainage system in late June. The subsequent development and maintenance of a channelled subglacial network are dependent upon sustained high rates of surface melting maintaining high supraglacial inputs. In a consistently warm summer (2000), subglacial drainage became rapidly and persistently channelled. In a cooler summer (2001), distributed subglacial drainage predominated. These observations confirm that supraglacial meltwater can access the bed of a High Arctic glacier in summer, and induce significant structural evolution of the subglacial drainage system. They do not support the view that subglacial drainage systems beneath polythermal glaciers are always poorly developed. They do suggest that the effects on ice flow of surface water penetration to the bed of predominantly cold glaciers may be short-lived.

scholarly journals Tidewater calving

1996 ◽  
Vol 42 (141) ◽  
pp. 375-385 ◽  
Author(s):  
С.J. Van Der Veen
Keyword(s):  
Water Depth ◽  
Fold Increase ◽  
Actual Rate ◽  
Tidewater Glaciers ◽  
Glacier Terminus ◽  
Tidewater Glacier ◽  
Iceberg Calving ◽  
Speed Up ◽  
Calving Rate ◽  
Subglacial Drainage

AbstractData from Columbia Glacier are used to identify processes that control calving from a temperate tidewater glacier and to re-evaluate models that have been proposed to describe iceberg calving. Since 1981, Columbia Glacier has been retreating rapidly, with an almost seven-fold increase in calving rate from the mid-1970s to 1993. At the same time, the speed of the glacier increased almost as much, so that the actual rate of retreat increased more slowly. According to the commonly accepted model, the calving rate is linearly related to the water depth at the terminus, with retreat of the glacier snout into deeper water, leading to larger calving rates and accelerated retreat. The Columbia Glacier data show that the calving rate is not simply linked to observed quantities such as water depth or stretching rate near the terminus. During the retreat, the thickness at the terminus appears to be linearly correlated with the water depth; at the terminus, the thickness in excess of flotation remained at about 50 m. This suggests that retreat may be initiated when the terminal thickness becomes too small, with the rate of retreat controlled by the rate at which the snout is thinning and by the basal slope. The implication is that the rapid retreat of Columbia Glacier (and other comparable tidewater glaciers) is not the result of an increase in calving as the glacier retreated into deeper water. Instead, the retreat was initiated and maintained by thinning of the glacier. For Columbia Glacier, the continued thinning is probably associated with the increase in glacier speed and retreat may be expected to continue as long as these large speeds are maintained. It is not clear what mechanism may be responsible for the speed-up but the most likely candidate is a change in basal conditions or subglacial drainage. Consequently, the behavior of tidewater glaciers may be controlled by processes acting at the glacier bed rather than by what happens at the glacier terminus.

scholarly journals Seasonal Variations in the Flow of Land-Terminating Glaciers in Central-West Greenland Using Sentinel-1 Imagery

2018 ◽  
Vol 10 (12) ◽  
pp. 1878 ◽  
Author(s):  
Adriano Lemos ◽  
Andrew Shepherd ◽  
Malcolm McMillan ◽  
Anna Hogg
Keyword(s):  
Ice Sheet ◽  
Drainage System ◽  
Greenland Ice Sheet ◽  
Sheet Flow ◽  
Altitudinal Variation ◽  
Weekly Basis ◽  
Ice Flow ◽  
Temporal Sampling ◽  
First Time ◽  
Subglacial Drainage

Land-terminating sectors of the Greenland ice sheet flow faster in summer after surface meltwater reaches the subglacial drainage system. Speedup occurs when the subglacial drainage system becomes saturated, leading to a reduction in the effective pressure which promotes sliding of the overlying ice. Here, we use observations acquired by the Sentinel-1a and b synthetic aperture radar to track changes in the speed of land-terminating glaciers across a 14,000 km2 sector of west-central Greenland on a weekly basis in 2016 and 2017. The fine spatial and temporal sampling of the satellite data allows us to map the speed of summer and winter across the entire sector and to resolve the weekly evolution of ice flow across the downstream portions of five glaciers. Near to the ice sheet margin (at 650 m.a.s.l.), glacier speedup begins around day 130, persisting for around 90 days, and then peaks around day 150. At four of the five glaciers included in our survey the peak speedup is similar in both years, in Russell Glacier there is marked interannual variability of 32% between 2016 and 2017. We present, for the first time, seasonal and altitudinal variation in speedup persistence. Our study demonstrates the value of Sentinel-1’s systematic and frequent acquisition plan for studying seasonal changes in ice sheet flow.

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