Investigation of recent oceanic contributions to instability of the Thwaites and Pine Island Glaciers

Abstract

The Antarctic ice shelves around the Amundsen Sea has experienced the fastest melting together with the rapid grounding line retreat in recent decades driven by the incursion of relatively warm Circumpolar Deep Water (CDW) into the sub-ice shelves. The Thwaites and Pine Island Glaciers have had attentions due to the most apparent thinning among the western Antarctic ice shelves. The Antarctic survey was done in the Pine Island Bay from January 29 to February 15, 2020 aboard the ice-breaking research vessel ARAON to evaluate recent oceanic contributions to instability of the Thwaites and Pine Island Glaciers. Through this survey, in-situ data from 89 full-depth CTD/LADCP profiling were collected near and off the ice shelves where we considered small basins, ridges, and troughs found based on high-resolution bathymetry data along with sea ice distributions. In this presentation, we propose three key findings: 1) CDW pathways below 700 m and heat transport into the two sub-ice shelves are primarily controlled by bed topography; 2) Horizontal ocean circulation in the Pine Island Bay plays an important role in distributing and redistributing heat within the bay and into the ice shelves that is changed due to the Pine Island Glacier ice front retreat. 3) The glacial meltwater flowing out from the two glaciers shape spatial and temporal variability of meltwater fraction at the upper (shallower than 500 m) ocean near and off the ice shelves. We discuss the observational results from 2020 survey in the context of the decadal variability.