No abstract

[1] Subglacial Lake Ellsworth has been proposed as a candidate for direct measurement and sampling, to identify microbial life and extract sedimentary climate records. We present a detailed characterization of the physiography of this subglacial lake from geophysical surveys, allowing bathymetry and geomorphic setting to be established. Lake Ellsworth is 14.7 km × 3.1 km with an area of 28.9 km 2 . Lake depth increases downlake from 52 m to 156 m, with a water body volume of 1.37 km 3 . The ice thickness suggests an unusual thermodynamic characteristic, with the critical pressure boundary intersecting the lake. Numerical modeling of water circulation has allowed accretion of basal ice to be estimated. We collate this physiographic and modeling information to confirm that Lake Ellsworth is ideal for direct access and propose an optimal drill site. The likelihood of dissolved gas exchange between the lake and the borehole is also assessed. Citation:

The West Antarctic Ice Sheet (WAIS) is considered the major contributor to global sea level rise in the Last Interglacial (LIG) and potentially in the future. Exposed fossil reef terraces suggest sea levels in excess of 7 m in the last warm era, of which probably not much more than 2 m are considered to originate from melting of the Greenland Ice Sheet. We simulate the evolution of the Antarctic Ice Sheet during the LIG with a 3‐D thermomechanical ice sheet model forced by an atmosphere‐ocean general circulation model (AOGCM). Our results show that high LIG sea levels cannot be reproduced with the atmosphere‐ocean forcing delivered by current AOGCMs. However, when taking reconstructed Southern Ocean temperature anomalies of several degrees, sensitivity studies indicate a Southern Ocean temperature anomaly threshold for total WAIS collapse of 2–3°C, accounting for a sea level rise of 3–4 m during the LIG. Potential future Antarctic Ice Sheet dynamics range from a moderate retreat to a complete collapse, depending on rate and amplitude of warming.

Abstract. Simulations of the ocean dynamics in the cavity under the Amery Ice Shelf, Antarctica, were carried out using a three-dimensional numerical ocean model. Two different boundary conditions were used to describe the open ocean barotropic exchange at the ice front. The simulations show that the circulation in the ocean cavity is predominantly barotropic and is generally steered by the cavity topography. The circulation is driven by the density gradient in the cavity, which is strongly influenced by the heat and salt fluxes from melting and freezing processes at the ice-ocean interface, and by the horizontal exchange of heat and salt across the open ocean boundary at the ice front. The interaction at the ice-ocean interface allows the basal component of the mass loss of the Amery Ice Shelf to be estimated.In the two simulations the computed losses were 5.8 Gt yr -1 and 18.0 Gt yr -1, values consistent with observations. The bulk of the melting occurred near the southern grounding line of the ice shelf, although substantial melting also occurred in areas where heat transport by horizontal circulation was large. Accretion was restricted to areas where water, from upstream melting, became supercooled as it ascended the ice shelf base.

No abstract