scholarly journals Subglacial bathymetry and sediment layer distribution beneath the Pine Island Glacier ice shelf, West Antarctica, modeled using aerogravity and autonomous underwater vehicle data

2013 ◽  
Vol 54 (64) ◽  
pp. 27-32 ◽  
Author(s):  
Atsuhiro Muto ◽  
Sidhar Anandakrishnan ◽  
Richard B. Alley
Keyword(s):  
Autonomous Underwater Vehicle ◽  
Underwater Vehicle ◽  
Flow Speed ◽  
Ocean Bottom ◽  
Sediment Layer ◽  
West Antarctica ◽  
Ice Shelf ◽  
The North ◽  
Submarine Ridge ◽  
Glacier Ice

Abstract Pine Island Glacier (PIG), West Antarctica, has been experiencing acceleration in its flow speed and mass loss for nearly two decades, driven in part by an increase in the delivery of relatively warm Circumpolar Deep Water (CDW). However, at present, the configuration of the sub-ice-shelf cavity and bed conditions beneath the PIG ice shelf that dictate such oceanic influences remain poorly understood. Here, we use aerogravity data and ocean bottom depths measured by an autonomous underwater vehicle (AUV) to model the bathymetry and sediment layer thickness beneath the PIG ice shelf. Results reveal that the deep basins, previously found by AUV on both landward and seaward sides of a submarine ridge, extend substantially to the north and south. The water column thickness of the basins reaches 400-550 m on the landward side of the ridge and 500-600 m on the seaward side. The sediment layer covers the whole expanse of the seabed beneath the ice shelf, and the thickness is in the range ∼200-1000 m. The thinnest sediments (<200 m) are found on the seaward slope of the submarine ridge, suggesting that erosion by advancing ice may have been concentrated in the lee of the topographic high.

scholarly journals History of lower Pine Island Glacier, West Antarctica, from Landsat imagery

2002 ◽  
Vol 48 (163) ◽  
pp. 536-544 ◽  
Author(s):  
Robert A. Bindschadler
Keyword(s):  
Landsat Imagery ◽  
West Antarctica ◽  
Ice Shelf ◽  
Landsat Images ◽  
The North ◽  
Glacier Ice ◽  
History Of ◽  
Upper Bound Estimate ◽  
Full Period ◽  
Observation Period

AbstractA 28 year record of lower Pine Island Glacier, West Antarctica, constructed from 15 Landsat images, shows changes at the terminus, grounding zone and both margins. The north margin has expanded 5 km into the adjacent ice shelf in a sustained event that was underway in 1973 and may have begun in 1957. Between 1991 and 1997, this expansion ceased and a new region of rifting was created associated with an ice rise on the glacier’s floating tongue. Changes in the topography of a nearby ice rise are used to deduce an upper-bound estimate of a 134 m thinning of the adjacent ice shelf. On the south margin, widening was limited to 1 km over the observation period and is seen propagating downstream in an intermediate-dated image. New areas of crevassing are also evident in the grounding zone of the glacier. Ice loss by the calving of large tabular bergs vastly exceeds mass loss by calving of many small bergs. These observations are consistent with reported changes of the 1990s and indicate that changes in the flow of Pine Island Glacier have occurred over the full period of satellite observations.

scholarly journals Pathways and modification of warm water flowing beneath Thwaites Ice Shelf, West Antarctica

2021 ◽  
Vol 7 (15) ◽  
pp. eabd7254
Author(s):  
A. K. Wåhlin ◽  
A. G. C. Graham ◽  
K. A. Hogan ◽  
B. Y. Queste ◽  
L. Boehme ◽  
...  
Keyword(s):  
Autonomous Underwater Vehicle ◽  
Warm Water ◽  
West Antarctica ◽  
Spatial Property ◽  
Ice Shelf ◽  
Large Uncertainty ◽  
West Antarctic Ice Sheet ◽  
The North ◽  
West Antarctic ◽  
Direct Observations

Thwaites Glacier is the most rapidly changing outlet of the West Antarctic Ice Sheet and adds large uncertainty to 21st century sea-level rise predictions. Here, we present the first direct observations of ocean temperature, salinity, and oxygen beneath Thwaites Ice Shelf front, collected by an autonomous underwater vehicle. On the basis of these data, pathways and modification of water flowing into the cavity are identified. Deep water underneath the central ice shelf derives from a previously underestimated eastern branch of warm water entering the cavity from Pine Island Bay. Inflow of warm and outflow of melt-enriched waters are identified in two seafloor troughs to the north. Spatial property gradients highlight a previously unknown convergence zone in one trough, where different water masses meet and mix. Our observations show warm water impinging from all sides on pinning points critical to ice-shelf stability, a scenario that may lead to unpinning and retreat.

On the relation between ice thickness changes and glacier speed-up, with application to Pine Island Glacier in West Antarctica 

2021 ◽  
Author(s):  
Jan De Rydt ◽  
Ronja Reese ◽  
Fernando Paolo ◽  
G Hilmar Gudmundsson
Keyword(s):  
Numerical Solutions ◽  
Numerical Models ◽  
Flow Speed ◽  
Ice Thickness ◽  
West Antarctica ◽  
Ice Shelf ◽  
Ice Flow ◽  
Spatially Distributed ◽  
Speed Up ◽  
Induced Changes

<p>Pine Island Glacier in West Antarctica is among the fastest changing glaciers worldwide. Much of its fast-flowing central trunk is thinning and accelerating, a process thought to have been triggered by ocean-induced changes in ice-shelf buttressing. The measured acceleration in response to perturbations in ice thickness is a non-trivial manifestation of several poorly-understood physical processes, including the transmission of stresses between the ice and underlying bed. To enable robust projections of future ice flow, it is imperative that numerical models include an accurate representation of these processes. Here we combine the latest data with analytical and numerical solutions of SSA ice flow to show that the recent increase in flow speed of Pine Island Glacier is only compatible with observed patterns of thinning if a spatially distributed, predominantly plastic bed underlies large parts of the central glacier and its upstream tributaries.</p>

Warm water flow and mixing beneath Thwaites Glacier ice shelf, West Antarctica

2020 ◽  
Author(s):  
Anna Wåhlin ◽  
Bastien Queste ◽  
Alastair Graham ◽  
Kelly Hogan ◽  
Lars Boehme ◽  
...  
Keyword(s):  
Water Flow ◽  
Deep Water ◽  
Autonomous Underwater Vehicle ◽  
Warm Water ◽  
Ice Shelf ◽  
Mixing Processes ◽  
Spatial Gradients ◽  
West Antarctic ◽  
Warm Deep Water ◽  
Glacier Ice

<p>The fate of the West Antarctic Ice Sheet is the largest remaining uncertainty in predicting sea-level rise through the next century, and its most vulnerable and rapidly changing outlet is Thwaites Glacier . Because the seabed slope under the glacier is retrograde (downhill inland), ice discharge from Thwaites Glacier is potentially unstable to melting of the underside of its floating ice shelf and grounding line retreat, both of which are enhanced by warm ocean water circulating underneath the ice shelf. Recent observations show surprising spatial variations in melt rates, indicating significant knowledge gaps in our understanding of the processes at the base of the ice shelf. Here we present the first direct observations of ocean temperature, salinity, and oxygen underneath Thwaites ice shelf collected by an autonomous underwater vehicle, a Kongsberg Hugin AUV. These observations show that while the western part of Thwaites has outflow of meltwater-enriched circumpolar deep water found in the main trough leading to Thwaites, the deep water (> 1000 m) underneath the central part of the ice shelf is in connection with Pine Island Bay - a previously unknown westward branch of warm deep water flow. Mid-depth water (700 - 1000 m) enters the cavity from both sides of a buttressing point and large spatial gradients of salinity and temperature indicate that this is a region of active mixing processes. The observations challenge conceptual models of ice-ocean interactions at glacier grounding zones and identify a main buttressing point as a vulnerable region of change currently under attack by warm water inflow from all sides: a scenario that may lead to ungrounding and retreat more quickly than previously expected.</p>

scholarly journals Ocean mixing beneath Pine Island Glacier ice shelf, West Antarctica

2016 ◽  
Vol 121 (12) ◽  
pp. 8496-8510 ◽  
Author(s):  
Satoshi Kimura ◽  
Adrian Jenkins ◽  
Pierre Dutrieux ◽  
Alexander Forryan ◽  
Alberto C. Naveira Garabato ◽  
...  
Keyword(s):  
Ocean Mixing ◽  
West Antarctica ◽  
Ice Shelf ◽  
Glacier Ice

scholarly journals Autonomous Underwater Vehicle Exploration of the Ocean Cavity Beneath an Antarctic Ice Shelf

Oceanography ◽  
2012 ◽  
Vol 25 (3) ◽  
pp. 202-203 ◽  
Author(s):  
Adrian Jenkins ◽  
Pierre Dutrieux ◽  
Stan Jacobs ◽  
Steve McPhail ◽  
James Perrett ◽  
...  
Keyword(s):  
Autonomous Underwater Vehicle ◽  
Underwater Vehicle ◽  
Ice Shelf

Ice-Age Simulations with a Calving Ice-Sheet Model

1983 ◽  
Vol 20 (1) ◽  
pp. 30-48 ◽  
Author(s):  
David Pollard
Keyword(s):  
Deep Sea ◽  
Ice Sheet ◽  
Ice Age ◽  
West Antarctica ◽  
Ice Shelf ◽  
Basic Model ◽  
The North ◽  
Uncertain Model ◽  
Model Components ◽  
Model Phase

AbstractVariations of ice-sheet volume during the Quaternary ice ages are simulated using a simple ice-sheet model for the Northern Hemisphere. The basic model predicts ice thickness and bedrock deformation in a north-south cross section, with a prescribed snow-budget distribution shifted uniformly in space to represent the orbital perturbations. An ice calving parameterization crudely representing proglacial lakes or marine incursions can attack the ice whenever the tip drops below sea level. The model produces a large ∼ 100,000-yr response in fair agreement (correlation coefficient up to 0.8) with the δ18O deep-sea core records. To increase confidence in the results, several of the more uncertain model components are extended or replaced, using an alternative treatment of bedrock deformation, a more realistic ice-shelf model of ice calving, and a generalized parameterization for such features as the North Atlantic deglacial meltwater layer. Much the same ice-age simulations and agreement with the δ18O records, as with the original model, are still obtained. The model is run with different types of forcing to identify which aspect of the orbital forcing controls the phase of the 100,000-yr cycles. First, the model is shown to give a ∼ 100,000-yr response to nearly any kind of higher-frequency forcing. Although over the last 2-million yrs the model phase is mainly controlled by the precessional modulation due to eccentricity, over just the last 500,000 yr the observed phase can also be simulated with eccentricity held constant. A definite conclusion on the phase control of the real 100,000-yr cycles is prevented by uncertainty in the deep-sea core time scales before ∼600,000 yr B.P. The model is adapted to represent West Antarctica, and yields unforced internal oscillations with periods of about 50,000 yr.

scholarly journals Velocities of the Smith Glacier ice tongue and Dotson Ice Shelf, Walgreen Coast, Marie Byrd Land, West Antarctica

1994 ◽  
Vol 20 ◽  
pp. 101-109 ◽  
Author(s):  
B.K. Lucchitta ◽  
K.F. Mullins ◽  
C.E. Smith ◽  
J.G. Ferrigno
Keyword(s):  
Progressive Increase ◽  
West Antarctica ◽  
Velocity Measurements ◽  
Ice Shelf ◽  
Time Intervals ◽  
Time Period ◽  
Grounding Line ◽  
Glacier Ice

Velocity measurements were made for two time intervals on the Smith Glacier ice tongue (1973–88 and 1988–90) and three on the Dotson Ice Shelf (1972–88, 1973–88 and 1988–90). The Smith Glacier ice tongue velocities for the two intervals are similar near the grounding line but show a progressive increase toward the terminus in the late 1980s. The Dotson Ice Shelf velocities remained virtually constant during all three time intervals. The increased velocities of the Smith Glacier ice tongue may be attributed to a general loss of densely packed icebergs that buttressed the terminus during the 1970s but drifted out to sea during the late 1980s. The Smith Glacier ice tongue receded as much as 10 km between 1973 and 1988, the Dotson lee Shelf 5–7 km in the same time period. Similar observations of drifting and ca1ving were made for the adjacent Thwaites Glacier ice tongue. The cause of the loss of ice in the region is unknown but it may have been a change in winds or a warming of the air or water during the late 1980s.

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