scholarly journals Ice stream subglacial access for ice-sheet history and fast ice flow: the BEAMISH Project on Rutford Ice Stream, West Antarctica and initial results on basal conditions

2020 ◽  
pp. 1-9
Author(s):  
A. M. Smith ◽  
P. G. D. Anker ◽  
K. W. Nicholls ◽  
K. Makinson ◽  
T. Murray ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Hot Water ◽  
Ice Flow ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Ice Stream ◽  
Hydrological System ◽  
History Of ◽  
Fast Ice ◽  
Water Saturated

Abstract Three holes were drilled to the bed of Rutford Ice Stream, through ice up to 2154 m thick, to investigate the basal processes and conditions associated with fast ice flow and the glacial history of the West Antarctic Ice Sheet. A narrative of the drilling, measuring and sampling activities, as well as some preliminary results and initial interpretations of subglacial conditions, is given. These were the deepest subglacial access holes ever drilled using the hot-water drilling method. Samples of bed and englacial sediments were recovered, and a number of instruments were installed in the ice column and the bed. The ice–bed interface was found to be unfrozen, with an existing, well-developed subglacial hydrological system at high pressure, within ~1% of the ice overburden. The bed itself comprises soft, water-saturated sediments, consistent with previous geophysical interpretations. Englacial sediment quantity varies significantly between two locations ~2 km apart, and possibly over even shorter (~20 m) distances. Difficulties and unusual observations encountered while connecting to the subglacial hydrological system in one hole possibly resulted from the presence of a large clast embedded in the bottom of the ice.

scholarly journals Kamb Ice Stream flow history and surge potential

2013 ◽  
Vol 54 (63) ◽  
pp. 287-298 ◽  
Author(s):  
Hermann Engelhardt ◽  
Barclay Kamb
Keyword(s):  
Video Camera ◽  
Hot Water ◽  
West Antarctica ◽  
Time Intervals ◽  
Ice Flow ◽  
Ice Stream ◽  
History Of ◽  
Fast Ice ◽  
Fast Motion ◽  
Kamb Ice Stream

AbstractA basal zone, tens of meters thick, of debris-laden ice was observed in Kamb Ice Stream, West Antarctica, using a video camera lowered into boreholes made by hot-water drilling. The debris content varies, sometimes abruptly, forming a sequence of layers that reflect the complex history of fast ice flow and bed interaction. In most parts, the concentration of debris is low, a few percent by weight, with particles, often mud clots, dispersed in a matrix of clear ice. The nature of the debris distribution can be interpreted in terms of specific time intervals in the history of fast motion of Kamb Ice Stream including processes leading up to the termination of its streaming behavior and possible reactivation.

scholarly journals Drivers of abrupt Holocene shifts in West Antarctic ice stream direction determined from combined ice sheet modelling and geologic signatures

2014 ◽  
Vol 26 (6) ◽  
pp. 674-686 ◽  
Author(s):  
C.J. Fogwill ◽  
C.S.M. Turney ◽  
N.R. Golledge ◽  
D.H. Rood ◽  
K. Hippe ◽  
...  
Keyword(s):  
Flow Direction ◽  
Ice Sheet ◽  
Weddell Sea ◽  
Last Deglaciation ◽  
Ice Streams ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Ice Stream ◽  
Ice Sheet Modelling

AbstractDetermining the millennial-scale behaviour of marine-based sectors of the West Antarctic Ice Sheet (WAIS) is critical to improve predictions of the future contribution of Antarctica to sea level rise. Here high-resolution ice sheet modelling was combined with new terrestrial geological constraints (in situ14C and 10Be analysis) to reconstruct the evolution of two major ice streams entering the Weddell Sea over 20 000 years. The results demonstrate how marked differences in ice flux at the marine margin of the expanded Antarctic ice sheet led to a major reorganization of ice streams in the Weddell Sea during the last deglaciation, resulting in the eastward migration of the Institute Ice Stream, triggering a significant regional change in ice sheet mass balance during the early to mid Holocene. The findings highlight how spatial variability in ice flow can cause marked changes in the pattern, flux and flow direction of ice streams on millennial timescales in this marine ice sheet setting. Given that this sector of the WAIS is assumed to be sensitive to ocean-forced instability and may be influenced by predicted twenty-first century ocean warming, our ability to model and predict abrupt and extensive ice stream diversions is key to a realistic assessment of future ice sheet sensitivity.

scholarly journals Of isbræ and ice streams

2003 ◽  
Vol 36 ◽  
pp. 66-72 ◽  
Author(s):  
Martin Truffer ◽  
Keith A. Echelmeyer
Keyword(s):  
Ice Sheet ◽  
Shear Zones ◽  
West Antarctica ◽  
Ice Streams ◽  
Ice Flow ◽  
Bed Topography ◽  
Ice Stream ◽  
Fast Ice ◽  
Fast Flow ◽  
End Members

AbstractFast-flowing ice streams and outlet glaciers provide the major avenues for ice flow from past and present ice sheets. These ice streams move faster than the surrounding ice sheet by a factor of 100 or more. Several mechanisms for fast ice-stream flow have been identified, leading to a spectrum of different ice-stream types. In this paper we discuss the two end members of this spectrum, which we term the “ice-stream” type (represented by the Siple Coast ice streams in West Antarctica) and the “isbræ” type (represented by Jakobshavn Isbræ in Greenland). The typical ice stream is wide, relatively shallow (∼1000 m), has a low surface slope and driving stress (∼10 kPa), and ice-stream location is not strongly controlled by bed topography. Fast flow is possible because the ice stream has a slippery bed, possibly underlain by weak, actively deforming sediments. The marginal shear zones are narrow and support most of the driving stress, and the ice deforms almost exclusively by transverse shear. The margins seem to be inherently unstable; they migrate, and there are plausible mechanisms for such ice streams to shut down. The isbræ type of ice stream is characterized by very high driving stresses, often exceeding 200 kPa. They flow through deep bedrock channels that are significantly deeper than the surrounding ice, and have steep surface slopes. Ice deformation includes vertical as well as lateral shear, and basal motion need not contribute significantly to the overall motion. The marginal shear zone stend to be wide relative to the isbræ width, and the location of isbræ and its margins is strongly controlled by bedrock topography. They are stable features, and can only shut down if the high ice flux cannot be supplied from the adjacent ice sheet. Isbræs occur in Greenland and East Antarctica, and possibly parts of Pine Island and Thwaites Glaciers, West Antarctica. In this paper, we compare and contrast the two types of ice streams, addressing questions such as ice deformation, basal motion, subglacial hydrology, seasonality of ice flow, and stability of the ice streams.

Deglacial history of the West Antarctic Ice Sheet in the Weddell Sea embayment: Constraints on past ice volume change

Geology ◽  
2010 ◽  
Vol 38 (5) ◽  
pp. 411-414 ◽  
Author(s):  
Michael J. Bentley ◽  
Christopher J. Fogwill ◽  
Anne M. Le Brocq ◽  
Alun L. Hubbard ◽  
David E. Sugden ◽  
...  
Keyword(s):  
Volume Change ◽  
Ice Sheet ◽  
Weddell Sea ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
Ice Volume ◽  
West Antarctic ◽  
History Of

scholarly journals Ice sheets viewed from the ocean: the contribution of marine science to understanding modern and past ice sheets

2012 ◽  
Vol 370 (1980) ◽  
pp. 5512-5539 ◽  
Author(s):  
Colm Ó Cofaigh
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Major Influence ◽  
Marine Science ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Technological Advances ◽  
Polar Ice Sheets ◽  
History Of ◽  
Geophysical Imaging

Over the last two decades, marine science, aided by technological advances in sediment coring, geophysical imaging and remotely operated submersibles, has played a major role in the investigation of contemporary and former ice sheets. Notable advances have been achieved with respect to reconstructing the extent and flow dynamics of the large polar ice sheets and their mid-latitude counterparts during the Quaternary from marine geophysical and geological records of landforms and sediments on glacier-influenced continental margins. Investigations of the deep-sea ice-rafted debris record have demonstrated that catastrophic collapse of large (10 5 –10 6  km 2 ) ice-sheet drainage basins occurred on millennial and shorter time scales and had a major influence on oceanography. In the last few years, increasing emphasis has been placed on understanding physical processes at the ice–ocean interface, particularly at the grounding line, and on determining how these processes affect ice-sheet stability. This remains a major challenge, however, owing to the logistical constraints imposed by working in ice-infested polar waters and ice-shelf cavities. Furthermore, despite advances in reconstructing the Quaternary history of mid- and high-latitude ice sheets, major unanswered questions remain regarding West Antarctic ice-sheet stability, and the long-term offshore history of the East Antarctic and Greenland ice sheets remains poorly constrained. While these are major research frontiers in glaciology, and ones in which marine science has a pivotal role to play, realizing such future advances will require an integrated collaborative approach between oceanographers, glaciologists, marine geologists and numerical modellers.

scholarly journals Formational history of the Wicklow Trough: a marine‐transgressed tunnel valley revealing ice flow velocity and retreat rates for the largest ice stream draining the late‐Devensian British–Irish Ice Sheet

2020 ◽  
Vol 35 (7) ◽  
pp. 907-919 ◽  
Author(s):  
Mark Coughlan ◽  
Zsuzsanna TÓth ◽  
Katrien J. J. Van Landeghem ◽  
Stephen Mccarron ◽  
Andrew J. Wheeler
Keyword(s):  
Flow Velocity ◽  
Ice Sheet ◽  
Ice Flow ◽  
Ice Stream ◽  
History Of

scholarly journals Seismic Measurement of the Gross Crystalline Structure of a West Antarctic Ice Stream (Abstract)

1988 ◽  
Vol 11 ◽  
pp. 199 ◽  
Author(s):  
D. D. Blankenship ◽  
C. R. Bentley
Keyword(s):  
Crystalline Structure ◽  
Ice Sheet ◽  
Ice Shelf ◽  
P Waves ◽  
Axis Orientation ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Ice Stream ◽  
Ice Stream B ◽  
Longitudinal Extension

Both in the interior of West Antarctica and on Ross Ice Shelf the ice column is dominated by ice with a distinct preferred c-axis orientation. An understanding of the dynamics of the West Antarctic ice sheet requires that we know the gross crystalline structure that characterizes each of its glaciological regimes (i.e. ice sheet, ice stream, and ice shelf). An important question is whether the strong fabric of the interior ice is preserved when this ice passes through the zone in which it is accelerated from sheet flow to stream flow, a zone that must be marked by strong longitudinal extension. Using generalized inverse techniques we have inverted seismic-reflection travel times observed at Upstream Β camp (on Ice Stream B) to obtain the gross crystalline structure of the ice column at that location. We find that the strong fabrics of the interior are indeed destroyed; only a slight preferred orientation remains. The evidence at Upstream Β camp is particularly strong because shear waves of both polarizations, which are particularly sensitive indicators of anisotropy, were analyzed as well as P-waves.

scholarly journals Subglacial thermal balance permits ongoing grounding-line retreat along the Siple Coast of West Antarctica

2003 ◽  
Vol 36 ◽  
pp. 251-256 ◽  
Author(s):  
Byron R. Parizek ◽  
Richard B. Alley ◽  
Christina L. Hulbe
Keyword(s):  
Sea Level ◽  
Water Distribution ◽  
Regulation Mechanism ◽  
Ice Streams ◽  
West Antarctic Ice Sheet ◽  
West Antarctic ◽  
Ice Stream ◽  
Grounding Line ◽  
History Of ◽  
Global Sea Level

AbstractChanges in the discharge of West Antarctic ice streams are of potential concern with respect to global sea level. The six relatively thin, fast-flowing Ross ice streams are of interest as low-slope end-members among Antarctic ice streams. Extensive research has demonstrated that these “rivers of ice” have a history of relatively high-frequency , asynchronous discharge variations with evolving lateral boundaries. Amidst this variability, a ∼1300 km grounding-line retreat has occurred since the Last Glacial Maximum. Numerical studies of Ice Stream D (Parizek and others, 2002) indicate that a proposed thermal-regulation mechanism (Clarke and Marshall, 1998; Hulbe and MacAyeal, 1999; Tulaczyk and others, 2000a, b), which could buffer the West Antarctic ice sheet against complete collapse, may be over-ridden by latent-heat transport within melt-water from beneath inland ice. Extending these studies to Ice Stream A, Whillans Ice Stream and Ice Stream C suggests that further grounding-line retreat contributing to sea-level rise is possible thermodynamically However, the efficiency of basal water distribution may be a constraint on the system. Because local thermal deficits promote basal freeze-on (especially on topographic highs), observed short-term variability is likely to persist.

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