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

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

scholarly journals Properties of a marine ice layer under the Amery Ice Shelf, East Antarctica

2009 ◽  
Vol 55 (192) ◽  
pp. 717-728 ◽  
Author(s):  
Mike Craven ◽  
Ian Allison ◽  
Helen Amanda Fricker ◽  
Roland Warner
Keyword(s):  
Sea Water ◽  
Average Rate ◽  
East Antarctica ◽  
Ice Shelf ◽  
Closure Rate ◽  
Southern Limit ◽  
Amery Ice Shelf ◽  
Average Porosity ◽  
Grounding Line ◽  
Ocean Properties

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.

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

2014 ◽  
Vol 8 (3) ◽  
pp. 1057-1068 ◽  
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.

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

2015 ◽  
Vol 120 (4) ◽  
pp. 3098-3112 ◽  
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

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

2008 ◽  
Vol 54 (184) ◽  
pp. 17-27 ◽  
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.

scholarly journals The cavity under the Amery Ice Shelf, East Antarctica

2008 ◽  
Vol 54 (188) ◽  
pp. 881-887 ◽  
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.

scholarly journals Large flux of iron from the Amery Ice Shelf marine ice to Prydz Bay, East Antarctica

2016 ◽  
Vol 121 (8) ◽  
pp. 6009-6020 ◽  
Author(s):  
L. Herraiz-Borreguero ◽  
D. Lannuzel ◽  
P. van der Merwe ◽  
A. Treverrow ◽  
J. B. Pedro
Keyword(s):  
East Antarctica ◽  
Prydz Bay ◽  
Ice Shelf ◽  
Amery Ice Shelf

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

2021 ◽  
Author(s):  
Roland C. Warner ◽  
Helen A. Fricker ◽  
Susheel Adusumilli ◽  
Philipp Arndt ◽  
Jonathan Kingslake ◽  
...  
Keyword(s):  
East Antarctica ◽  
Ice Shelf ◽  
Amery Ice Shelf ◽  
Rapid Formation

On the modified Circumpolar Deep Water upwelling over the Four Ladies Bank in Prydz Bay, East Antarctica

2020 ◽  
Author(s):  
Chengyan Liu ◽  
Zhaomin Wang ◽  
Chen Cheng ◽  
Xi Liang ◽  
Yang Wu ◽  
...  
Keyword(s):  
Heat Flux ◽  
Standard Deviation ◽  
Kinetic Energy ◽  
Potential Temperature ◽  
Weddell Sea ◽  
East Antarctica ◽  
Prydz Bay ◽  
Ice Shelf ◽  
Borehole Data ◽  
Amery Ice Shelf

<p>We report on mooring observations of tidal currents in Prydz Bay, East Antarctica. Tides in Prydz Bay are mixed diurnal-semidiurnal and much weaker than that in the Ross Sea and the Weddell Sea, with the spatial and temporal averaged value of 2.58 cm s<sup>-1</sup> for all the current meter observations over the continental shelf. The major axes of the tidal ellipses are generally aligned south-north, probably steered by the topography. The tidal phases are modulated by both the baroclinic and barotropic tidal components. The averaged tidal kinetic energy can account for a fraction of ~13% with respect to the total kinetic energy at the Amery Ice Shelf calving front during the observing period. The long-term average tidal heat flux across the Amery Ice Shelf calving front is negligible, but the ratio of the tidal heat flux standard deviation to the residual heat flux standard deviation can be up to 41%. We also report on borehole observations of tide-like pulsing of potential temperature and salinity, indicating the indispensable tidal influences in the ice-ocean boundary layer. These mooring and borehole data support that the tidal processes should be highlighted in the investigations of the interaction between the Amery Ice Shelf and ocean.</p>

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