Bathymetry beneath the Amery ice shelf, East Antarctica, revealed by airborne gravity

AbstractThe Amery Ice Shelf, East Antarctica, undergoes high basal melt rates near the southern limit of its grounding line where 80% of the ice melts within 240 km of becoming afloat. A considerable portion of this later refreezes downstream as marine ice. This produces a marine ice layer up to 200 m thick in the northwest sector of the ice shelf concentrated in a pair of longitudinal bands that extend some 200 km all the way to the calving front. We drilled through the eastern marine ice band at two locations 70 km apart on the same flowline. We determine an average accretion rate of marine ice of 1.1 ± 0.2 m a−1, at a reference density of 920 kg m−3 between borehole sites, and infer a similar average rate of 1.3 ± 0.2 m a−1 upstream. The deeper marine ice was permeable enough that a hydraulic connection was made whilst the drill was still 70–100 m above the ice-shelf base. Below this marine close-off depth, borehole video imagery showed permeable ice with water-filled cavities and individual ice platelets fused together, while the upper marine ice was impermeable with small brine-cell inclusions. We infer that the uppermost portion of the permeable ice becomes impermeable with the passage of time and as more marine ice is accreted on the base of the shelf. We estimate an average closure rate of 0.3 m a−1 between the borehole sites; upstream the average closure rate is faster at 0.9 m a−1. We estimate an average porosity of the total marine ice layer of 14–20%, such that the deeper ice must have even higher values. High permeability implies that sea water can move relatively freely through the material, and we propose that where such marine ice exists this renders deep parts of the ice shelf particularly vulnerable to changes in ocean properties.

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Modelling the response of the Lambert Glacier–Amery Ice Shelf system, East Antarctica, to uncertain climate forcing over the 21st and 22nd centuries

The Cryosphere ◽

10.5194/tc-8-1057-2014 ◽

2014 ◽

Vol 8 (3) ◽

pp. 1057-1068 ◽

Cited By ~ 20

Author(s):

Y. Gong ◽

S. L. Cornford ◽

A. J. Payne

Keyword(s):

Climate Model ◽

Global Environmental Change ◽

Ice Sheet ◽

Adaptive Mesh ◽

Ocean Model ◽

East Antarctica ◽

Ice Shelf ◽

Amery Ice Shelf ◽

Grounding Line ◽

Lambert Glacier

Abstract. The interaction between the climate system and the large polar ice sheet regions is a key process in global environmental change. We carried out dynamic ice simulations of one of the largest drainage systems in East Antarctica: the Lambert Glacier–Amery Ice Shelf system, with an adaptive mesh ice sheet model. The ice sheet model is driven by surface accumulation and basal melt rates computed by the FESOM (Finite-Element Sea-Ice Ocean Model) ocean model and the RACMO2 (Regional Atmospheric Climate Model) and LMDZ4 (Laboratoire de Météorologie Dynamique Zoom) atmosphere models. The change of ice thickness and velocity in the ice shelf is mainly influenced by the basal melt distribution, but, although the ice shelf thins in most of the simulations, there is little grounding line retreat. We find that the Lambert Glacier grounding line can retreat as much as 40 km if there is sufficient thinning of the ice shelf south of Clemence Massif, but the ocean model does not provide sufficiently high melt rates in that region. Overall, the increased accumulation computed by the atmosphere models outweighs ice stream acceleration so that the net contribution to sea level rise is negative.

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Protists in the marine ice of the Amery Ice Shelf, East Antarctica

Polar Biology ◽

10.1007/s00300-006-0169-7 ◽

2006 ◽

Vol 30 (2) ◽

pp. 143-153 ◽

Cited By ~ 24

Author(s):

D. Roberts ◽

M. Craven ◽

Minghong Cai ◽

I. Allison ◽

G. Nash

Keyword(s):

East Antarctica ◽

Ice Shelf ◽

Amery Ice Shelf

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Circulation of modified Circumpolar Deep Water and basal melt beneath the Amery Ice Shelf, East Antarctica

Journal of Geophysical Research Oceans ◽

10.1002/2015jc010697 ◽

2015 ◽

Vol 120 (4) ◽

pp. 3098-3112 ◽

Cited By ~ 23

Author(s):

Laura Herraiz-Borreguero ◽

Richard Coleman ◽

Ian Allison ◽

Stephen R. Rintoul ◽

Mike Craven ◽

...

Keyword(s):

Deep Water ◽

East Antarctica ◽

Ice Shelf ◽

Circumpolar Deep Water ◽

Amery Ice Shelf

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Multi-year monitoring of rift propagation on the Amery Ice Shelf, East Antarctica

Geophysical Research Letters ◽

10.1029/2004gl021036 ◽

2005 ◽

Vol 32 (2) ◽

Cited By ~ 36

Author(s):

H. A. Fricker

Keyword(s):

East Antarctica ◽

Ice Shelf ◽

Amery Ice Shelf ◽

Rift Propagation

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An investigation into the forces that drive ice-shelf rift propagation on the Amery Ice Shelf, East Antarctica

Journal of Glaciology ◽

10.3189/002214308784409116 ◽

2008 ◽

Vol 54 (184) ◽

pp. 17-27 ◽

Cited By ~ 52

Author(s):

Jeremy N. Bassis ◽

Helen A. Fricker ◽

Richard Coleman ◽

Jean-Bernard Minster

Keyword(s):

East Antarctica ◽

Force Balance ◽

Rift System ◽

Ice Shelf ◽

Short Term ◽

Ancillary Data ◽

Dominant Term ◽

Wind Speeds ◽

Amery Ice Shelf ◽

Rift Propagation

AbstractFor three field seasons (2002/03, 2004/05, 2005/06) we have deployed a network of GPS receivers and seismometers around the tip of a propagating rift on the Amery Ice Shelf, East Antarctica. During these campaigns we detected seven bursts of episodic rift propagation. To determine whether these rift propagation events were triggered by short-term environmental forcings, we analyzed simultaneous ancillary data such as wind speeds, tidal amplitudes and sea-ice fraction (a proxy variable for ocean swell). We find that none of these environmental forcings, separately or together, correlated with rift propagation. This apparent insensitivity of ice-shelf rift propagation to short-term environmental forcings leads us to suggest that the rifting process is primarily driven by the internal glaciological stress. Our hypothesis is supported by order-of-magnitude calculations that the glaciological stress is the dominant term in the force balance. However, our calculations also indicate that as the ice shelf thins or the rift system matures and iceberg detachment becomes imminent, short-term stresses due to winds and ocean swell may become more important.

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Geochemistry and geochronology of Mesoproterozoic basement rocks from the Eastern Amery Ice Shelf and southwestern Prydz Bay, East Antarctica: Implications for a long-lived magmatic accretion in a continental arc

American Journal of Science ◽

10.2475/02.2014.03 ◽

2014 ◽

Vol 314 (2) ◽

pp. 508-547 ◽

Cited By ~ 21

Author(s):

X. Liu ◽

B.-m. Jahn ◽

Y. Zhao ◽

J. Liu ◽

L. Ren

Keyword(s):

East Antarctica ◽

Prydz Bay ◽

Ice Shelf ◽

Amery Ice Shelf ◽

Basement Rocks ◽

Continental Arc

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The cavity under the Amery Ice Shelf, East Antarctica

Journal of Glaciology ◽

10.3189/002214308787779898 ◽

2008 ◽

Vol 54 (188) ◽

pp. 881-887 ◽

Cited By ~ 29

Author(s):

B.K. Galton-Fenzi ◽

C. Maraldi ◽

R. Coleman ◽

J. Hunter

Keyword(s):

Water Column ◽

Ocean Circulation ◽

East Antarctica ◽

Ocean Tide ◽

Ice Shelf ◽

Ice Shelves ◽

Ocean Tide Model ◽

Amery Ice Shelf ◽

Tidal Constituents

AbstractOcean circulation under ice shelves and associated rates of melting and freezing are strongly influenced by the shape of the sub-ice-shelf cavity. We have refined an existing method and used additional in situ measurements to estimate the cavity shape under the Amery Ice Shelf, East Antarctica. A finite-element hydrodynamic ocean-tide model was used to simulate the major tidal constituents for a range of different sub-Amery Ice Shelf cavity water-column thicknesses. The data are adjusted in the largely unsurveyed southern region of the ice-shelf cavity by comparing the complex error between simulated tides and in situ tides, derived from GPS observations. We show a significant improvement in the simulated tides, with a combined complex error of 1.8 cm, in comparison with past studies which show a complex error of ∼5.3 cm. Our bathymetry incorporates ice-draft data at the grounding line and seismic surveys, which have provided a considerable amount of new data. This technique has particular application when the water column beneath ice shelves is inaccessible and in situ GPS data are available.

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