Abstract
Abstract. Ice shelves play key roles in stabilizing Antarctica's ice sheets, maintaining its high albedo and returning freshwater to the Southern Ocean. Improved data sets of ice shelf draft and underlying bathymetry are important for assessing ocean–ice interactions and modeling ice response to climate change. The long, narrow Abbot Ice Shelf south of Thurston Island produces a large volume of meltwater, but is close to being in overall mass balance. Here we invert NASA Operation IceBridge (OIB) airborne gravity data over the Abbot region to obtain sub-ice bathymetry, and combine OIB elevation and ice thickness measurements to estimate ice draft. A series of asymmetric fault-bounded basins formed during rifting of Zealandia from Antarctica underlie the Abbot Ice Shelf west of 94° W and the Cosgrove Ice Shelf to the south. Sub-ice water column depths along OIB flight lines are sufficiently deep to allow warm deep and thermocline waters observed near the western Abbot ice front to circulate through much of the ice shelf cavity. An average ice shelf draft of ~200 m, 15% less than the Bedmap2 compilation, coincides with the summer transition between the ocean surface mixed layer and upper thermocline. Thick ice streams feeding the Abbot cross relatively stable grounding lines and are rapidly thinned by the warmest inflow. While the ice shelf is presently in equilibrium, the overall correspondence between draft distribution and thermocline depth indicates sensitivity to changes in characteristics of the ocean surface and deep waters.
Highlights
Ice shelves are found along much of the Antarctic coastline and make up about 11 % of the surface area of Antarctic ice (Fox and Cooper, 1994)
Many West Antarctic ice shelves, within the Amundsen Sea Embayment, immediately to the west of the Abbot Ice Shelf, have experienced rapid thinning (e.g., Rignot, 1998; Shepherd et al, 2004; Pritchard et al, 2012). Much of this thinning has been attributed to bottom melting resulting from relatively warm Circumpolar Deep Water (CDW) circulating on the continental shelf and beneath those ice shelves (e.g., Jacobs et al, 1996, 2011, 2013; Jenkins et al, 2010; Hellmer et al, 1998), and to unpinning from the sub-ice bathymetry (Jenkins et al, 2010)
The high-density body modeled along the southern margin of the ice shelf is nearly in line with a WNW–ESE-trending gravity anomaly located between 105 and 110◦ W on the continental shelf west of the Abbot (McAdoo and Laxon, 1997) (Fig. 2)
Summary
Ice shelves are found along much of the Antarctic coastline and make up about 11 % of the surface area of Antarctic ice (Fox and Cooper, 1994). Many West Antarctic ice shelves, within the Amundsen Sea Embayment, immediately to the west of the Abbot Ice Shelf, have experienced rapid thinning (e.g., Rignot, 1998; Shepherd et al, 2004; Pritchard et al, 2012). Much of this thinning has been attributed to bottom melting resulting from relatively warm Circumpolar Deep Water (CDW) circulating on the continental shelf and beneath those ice shelves (e.g., Jacobs et al, 1996, 2011, 2013; Jenkins et al, 2010; Hellmer et al, 1998), and to unpinning from the sub-ice bathymetry (Jenkins et al, 2010).
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