Oceanographic Controls on the Variability of Ice‐Shelf Basal Melting and Circulation of Glacial Meltwater in the Amundsen Sea Embayment, Antarctica

Abstract

Ice shelves in the Amundsen Sea Embayment have thinned, accelerating the seaward flow of ice sheets upstream over recent decades. This imbalance is caused by an increase in the ocean‐driven melting of the ice shelves. Observations and models show that the ocean heat content reaching the ice shelves is sensitive to the depth of thermocline, which separates the cool, fresh surface waters from warm, salty waters. Yet the processes controlling the variability of thermocline depth remain poorly constrained. Here we quantify the oceanic conditions and ocean‐driven melting of Cosgrove, Pine Island Glacier (PIG), Thwaites, Crosson, and Dotson ice shelves in the Amundsen Sea Embayment from 1991 to 2014 using a general circulation model. Ice‐shelf melting is coupled to variability in the wind field and the sea‐ice motions over the continental shelf break and associated onshore advection of warm waters in deep troughs. The layer of warm, salty waters at the calving front of PIG and Thwaites is thicker in austral spring (June–October) than in austral summer (December–March), whereas the seasonal cycle at the calving front of Dotson is reversed. Furthermore, the ocean‐driven melting in PIG is enhanced by an asymmetric response to changes in ocean heat transport anomalies at the continental shelf break: melting responds more rapidly to increases in ocean heat transport than to decreases. This asymmetry is caused by the inland deepening of bathymetry and the glacial meltwater circulation around the ice shelf.

Wind-Driven Processes Controlling Oceanic Heat Delivery to the Amundsen Sea, Antarctica

“…We employed monthly mean outputs of the ocean circulation model of Kimura et al (2017). Briefly, the simulation is based on the Massachusetts Institute of Technology general circulation model (MITgcm) adapted to include sub-ice-shelf cavities (Losch 2008) and coupled with a sea ice model based on a viscousplastic rheology (Losch et al 2010).…”

How Accurately Should We Model Ice Shelf Melt Rates?

“…Meanwhile, there has been a great deal of effort in the modeling of ice-ocean interactions in the Amundsen (e.g., Dutrieux et al, 2014;Kimura et al, 2017;Nakayama et al, 2017;Payne et al, 2007;Robertson, 2013;St-Laurent et al, 2015). While regional ocean models have been successful in reproducing ocean circulation 10.1029/2018GL080383 and its link to bulk ice-shelf melt, ice modeling suggest that the location of ice removal from an ice shelf, in addition to its bulk value, may impact its buttressing capacity (Arthern & Williams, 2017;Goldberg & Heimbach, 2013;Goldberg et al, 2012;Seroussi et al, 2017).…”

“…Meanwhile, there has been a great deal of effort in the modeling of ice-ocean interactions in the Amundsen (e.g., Dutrieux et al, 2014;Kimura et al, 2017;Nakayama et al, 2017;Payne et al, 2007;Robertson, 2013;St-Laurent et al, 2015). While regional ocean models have been successful in reproducing ocean circulation RESEARCH LETTER 10.1029/2018GL080383 Key Points: • Satellite measurement of melt rates shows high spatial variability under two fast-flowing ice shelves • Ice-sheet response to ice shelf melt depends on the pattern of melt rates as well as their spatial average • The ability of an ocean model to reproduce this pattern depends on accurate bathymetry and ice shelf draft data…”

Phased Response of the Subpolar Southern Ocean to Changes in Circumpolar Winds

“…This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. As a result of the sSO's environmental challenges to conventional observational approaches, our understanding of the regional ocean dynamics remains fragmentary and is founded primarily on a few long-term mooring records (Daae et al, 2018;Graham et al, 2013;Kim et al, 2016;Núñez-Riboni & Fahrbach, 2009;Peña-Molino et al, 2016;Webber et al, 2017) and numerical models (Kimura et al, 2017;Mathiot et al, 2011;Paloczy et al, 2018;Stewart & Thompson, 2015) as well as sparse hydrographic data (Hatterman, 2018;Mallett et al, 2018). These studies indicate that in many areas around Antarctica, the slope frontal system and on-shelf pycnocline exhibit pronounced seasonality, with wind forcing being consistently suggested as the primary causal factor.…”