Abstract
AbstractBasal melting of ice shelves is inherently difficult to quantify through direct observations, yet it is a critical factor controlling Antarctic mass balance and global sea‐level rise. While much research attention is paid to larger ice shelves and those experiencing the most rapid change, many smaller, unstudied ice shelves offer valuable insights. Here, we investigate the oceanographic conditions and melting beneath the Sørsdal ice shelf, East Antarctica. We present results from the 2018/2019 Sørsdal deployment of the University of Tasmania's autonomous underwater vehicle nupiri muka. Oceanography adjacent to and beneath the ice shelf front shows a cold and relatively saline environment dominated by Winter Water and Dense Shelf Water, while bathymetry measurements show a deep (∼1,200 m) trough running into the ice shelf cavity. Two multiyear deployments of Autonomous Phase‐sensitive Radar Echo Sounders on the surface of the ice shelf show weak melt rates (average of 1.6 and 2.3 m yr−1) with low temporal variability. These observations are supported by numerical ocean model and satellite estimates of melting. We speculate that the presence of a ∼825 m thick (350 m to at least 1,175 m) homogeneous layer of cold, dense water blocks access from warmer waters that intrude into Prydz Bay from offshore, resulting in weak melt rates. However, the newly identified trough means that the ice shelf is vulnerable to any decrease in polynya activity that allows warm water to enter the cavity. This could lead to increased basal melting and mass loss through this sector of Antarctica.
Highlights
Ocean-driven melting at the base of ice shelves is the main contributor to mass loss from the Antarctic Ice Sheet (Liu et al, 2015)
Oceanography adjacent to and beneath the ice shelf front shows a cold and relatively saline environment dominated by Winter Water and Dense Shelf Water, while bathymetry measurements show a deep (∼1,200 m) trough running into the ice shelf cavity
We present the results from a first-time deployment of an autonomous underwater vehicle (AUV) to the Sørsdal ice shelf in East Antarctica
Summary
Ocean-driven melting at the base of ice shelves is the main contributor to mass loss from the Antarctic Ice Sheet (Liu et al, 2015). Estimates of Antarctic mass loss in the recent period (2011–2017) range from 137 ± 25 gt yr−1 (Schröder et al, 2019) to 178 ± 23 gt yr−1 (Sasgen et al, 2019), bringing the total sea-level contribution from 1979–2017 to 13.9 ± 2.0 mm (Rignot et al, 2019). These rates have uncertainties that are magnified GWYTHER ET AL. Detection and attribution of change is made difficult by intrinsic, interannual, and decadal variability in oceanic and atmospheric forcing, which can obscure trends (Gwyther et al, 2018; Jenkins et al, 2018)
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