Mechanisms driving variability in the ocean forcing of Pine Island Glacier

Benjamin G M Webber,David P Stevens,Karen J Heywood,Tae Wan Kim,Adrian Jenkins,Pierre Dutrieux,Ho Kyung Ha,E Povl Abrahamsen,Sang Hoon Lee,Stanley S Jacobs

doi:10.1038/ncomms14507

Abstract

Pine Island Glacier (PIG) terminates in a rapidly melting ice shelf, and ocean circulation and temperature are implicated in the retreat and growing contribution to sea level rise of PIG and nearby glaciers. However, the variability of the ocean forcing of PIG has been poorly constrained due to a lack of multi-year observations. Here we show, using a unique record close to the Pine Island Ice Shelf (PIIS), that there is considerable oceanic variability at seasonal and interannual timescales, including a pronounced cold period from October 2011 to May 2013. This variability can be largely explained by two processes: cumulative ocean surface heat fluxes and sea ice formation close to PIIS; and interannual reversals in ocean currents and associated heat transport within Pine Island Bay, driven by a combination of local and remote forcing. Local atmospheric forcing therefore plays an important role in driving oceanic variability close to PIIS.

Highlights

Pine Island Glacier (PIG) terminates in a rapidly melting ice shelf, and ocean circulation and temperature are implicated in the retreat and growing contribution to sea level rise of PIG and nearby glaciers
The ocean-driven melting of the Pine Island Ice Shelf (PIIS) arises as a result of the relatively warm, salty circumpolar deep water (CDW) that floods the lower part of the water column across the Amundsen Sea continental shelf
The CDW that reaches PIIS appears to be a combination of water originating from both the central and eastern troughs[19], which join paths and mix before flowing southwards into Pine Island Bay (74–75°S, 105–100°W)

Summary

Introduction

Pine Island Glacier (PIG) terminates in a rapidly melting ice shelf, and ocean circulation and temperature are implicated in the retreat and growing contribution to sea level rise of PIG and nearby glaciers. The variability observed at BSR5/iSTAR9 represents large-scale changes that extend across Pine Island Bay. At the peak of the cold period in spring 2012, the total ocean heat content above freezing (see Methods) between 400 and 700 m at BSR5/iSTAR9 was 1.25 GJ, a 62% reduction from the

Results

Conclusion