Morphological evidence and direct estimates of rapid melting beneath Totten Glacier Ice Shelf, East Antarctica

• Main Authors: Greenbaum, J, Schroeder, D, Grima, C, Habbal, F, Dow, C, Roberts, J, Gwyther, D, van Ommen, TD, Siegert, M, Blankenship, D
• Format: Conference Object
• Language: English
• Published: Copernicus GmbH 2017
• Subjects: Earth Sciences; Oceanography; Physical Oceanography; Antarctic; East Antarctica; Greenland; Pine Island Glacier; Totten Glacier; West Antarctica; Antarc*; Antarctica; glacier; Ice Sheet; Ice Shelf; Ice Shelves; Pine Island
• Online Access: http://ecite.utas.edu.au/116899

Totten Glacier drains at least 3.5 meters of eustatic sea level potential from marine-based ice in the Aurora SubglacialBasin (ASB) in East Antarctica, more than the combined total of all glaciers in West Antarctica. TottenGlacier has been the most rapidly thinning glacier in East Antarctica since satellite altimetry time series beganand the nature of the thinning suggests that it is driven by enhanced basal melting due to ocean processes. Whilegrounded ice thinning rates have been steady, recent work has shown that Tottens floating ice shelf may not havethe same thinning behavior; as a result, it is critical to observe ice shelf and cavity boundary conditions and basalprocesses to understand this apparent discrepancy. Warm Modified Circumpolar Deep Water (MCDW), which hasbeen linked to glacier retreat in West Antarctica, has been observed in summer and winter on the nearby SabrinaCoast continental shelf and deep depressions in the seafloor provide access for MCDW to reach the ice shelf cavity.Given its northern latitude, numerical ice sheet modeling indicates that Totten Glacier may be prone to retreatcaused by hydrofracture in a warming climate, so it is important to understand how intruding MCDW is affectingthinning of Totten Glaciers ice shelf. Here we use post-processed, focused airborne radar observations of the TottenGlacier Ice Shelf to delineate multi-km wide basal channels and flat basal terraces associated with high basalreflectivity and specularity (flatness) anomalies and correspondingly large ice surface depressions that indicateactive basal melting. Using a simple temperature-attenuation model, and basal roughness corrections, we presentbasal melt rates associated with the radar reflection and specularity anomalies and compare them to those derivedfrom numerical ocean circulation modeling and an ice flow divergence calculation. Sub-ice shelf ocean circulationmodeling and under-ice robotic observations of Pine Island Glacier Ice Shelf in West Antarctica and the PetermannGlacier Ice Shelf in Greenland have shown that basal terraces associated with large basal channels are an indicationof rapidly melting ice shelves. In this context, these new results identify an East Antarctic example of rapid basalmelting processes and demonstrate that airborne radar can be used to identify basal characteristics and processesrelevant to ice shelf stability.