scholarly journals Rapid formation of an ice doline on Amery Ice Shelf, East Antarctica

Author(s):  
Roland C. Warner ◽  
Helen A. Fricker ◽  
Susheel Adusumilli ◽  
Philipp Arndt ◽  
Jonathan Kingslake ◽  
...  
2021 ◽  
Author(s):  
Roland C Warner ◽  
Helen A. Fricker ◽  
Susheel Adusumilli ◽  
Philipp Sebastian Arndt ◽  
Jonathan Kingslake ◽  
...  

2020 ◽  
Author(s):  
Roland C Warner ◽  
Helen A. Fricker ◽  
Susheel Adusumilli ◽  
Philipp Sebastian Arndt ◽  
Jonathan Kingslake ◽  
...  

2021 ◽  
Author(s):  
Roland Warner ◽  
Helen Fricker ◽  
Susheel Adusumilli ◽  
Philipp Arndt ◽  
Jonathan Kingslake ◽  
...  

<p>Surface meltwater accumulating on Antarctica’s floating ice shelves can drive fractures through to the ocean and potentially cause their collapse, leading to enhanced ice discharge from the continent. Surface melting in Antarctica is predicted to increase significantly during coming decades, but the implications for ice shelf stability are unknown. We are still learning how meltwater forms, flows and alters the surface, and that rapid water-driven changes are not limited to summer. The southern Amery Ice Shelf in East Antarctica already has an extensive surface meltwater system and provides us with an opportunity to study melt processes in detail. We present high-resolution satellite data (imagery, ICESat-2 altimetry and elevation models from WorldView stereo-photogrammetry) revealing an abrupt change extending across ~60 km<sup>2</sup> of the ice shelf surface in June 2019 (midwinter). We interpret this as drainage of an englacial lake through to the ocean below in less than three days. This left an uneven depression in the ice shelf surface, 11 km<sup>2</sup> in area and as much as 80 m deep, with a bed of fractured ice: an “ice doline”. The englacial lake had lain beneath the perennially ice-covered portion of a 20 km<sup>2</sup> meltwater lake. The reduced mass loading on the floating ice shelf after the drainage event resulted in flexure, with uplift of up to 36 m around the former lake. Applying an elastic flexural model to the uplift profiles suggests the loss of 0.75 km<sup>3 </sup>of water to the ocean. In summer 2020, we observed meltwater accumulating in a new lake basin created by the flexure. ICESat-2 observations profiled a new narrow meltwater channel (20 m wide and 3 m deep), rapidly incised inside the doline as meltwater spilled over from the new lake and started refilling the depression. This study demonstrates how high-resolution geodetic measurements from ICESat-2 and WorldView can explore critical fine-scale ice shelf processes. The insights gained will greatly improve our ability to model these processes, ultimately improving the accuracy of our projections.</p>


2009 ◽  
Vol 55 (192) ◽  
pp. 717-728 ◽  
Author(s):  
Mike Craven ◽  
Ian Allison ◽  
Helen Amanda Fricker ◽  
Roland Warner

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.


2014 ◽  
Vol 8 (3) ◽  
pp. 1057-1068 ◽  
Author(s):  
Y. Gong ◽  
S. L. Cornford ◽  
A. J. Payne

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.


Polar Biology ◽  
2006 ◽  
Vol 30 (2) ◽  
pp. 143-153 ◽  
Author(s):  
D. Roberts ◽  
M. Craven ◽  
Minghong Cai ◽  
I. Allison ◽  
G. Nash

2015 ◽  
Vol 120 (4) ◽  
pp. 3098-3112 ◽  
Author(s):  
Laura Herraiz-Borreguero ◽  
Richard Coleman ◽  
Ian Allison ◽  
Stephen R. Rintoul ◽  
Mike Craven ◽  
...  

2008 ◽  
Vol 54 (184) ◽  
pp. 17-27 ◽  
Author(s):  
Jeremy N. Bassis ◽  
Helen A. Fricker ◽  
Richard Coleman ◽  
Jean-Bernard Minster

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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