The Cryosphere Discuss., 7, 5509-5540, 2013
© Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper is under review for the journal The Cryosphere (TC).
Tectonic and oceanographic controls on Abbot Ice Shelf thickness and stability
J. R. Cochran, S. S. Jacobs, K. J. Tinto, and R. E. Bell
Lamont-Doherty Earth Observatory of Columbia University Palisades, NY 10964, USA

Abstract. Ice shelves play key roles in stabilizing Antarctica's ice sheets 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 large volumes of meltwater but is in overall mass balance unlike other ice shelves in the region that are losing mass. 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 rift basins underlie the Abbot Ice shelf west of 94° W and also the Cosgrove Ice Shelf to the south. The ice sheet bed in areas surrounding the Abbot is near or above sea level, consistent with stable grounding lines. Sub-ice water column depths along OIB flight lines are sufficiently deep to allow warm deep and thermocline waters near the western Abbot ice front to circulate through much of the ice shelf cavity. Abbot Ice Shelf drafts averaging ∼200 m, about 30 m less than the Bedmap2 compilation, are coincident with the summer transition between the ocean surface mixed layer and upper thermocline. The ice feeding the Abbot crosses the relatively stable southern grounding lines and is rapidly thinned by the warmest inflow. While the system is presently in equilibrium, the overall draft is sensitive to the thickness of the cold Antarctic surface water overlying the thermocline.

Citation: Cochran, J. R., Jacobs, S. S., Tinto, K. J., and Bell, R. E.: Tectonic and oceanographic controls on Abbot Ice Shelf thickness and stability, The Cryosphere Discuss., 7, 5509-5540, doi:10.5194/tcd-7-5509-2013, 2013.
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