Interplay of grounding-line dynamics and sub-shelf melting during retreat of the Bj\xf8rn\xf8yrenna Ice Stream

Michele Petrini,Anna L C Hughes,Emanuele Forte,Nina Kirchner,Michele Rebesco,Renata G Lucchi,Renato R Colucci,Angelo Camerlenghi,Riko Noormets,Florence Colleoni

doi:10.1038/s41598-018-25664-6

Abstract

The Barents Sea Ice Sheet was a marine-based ice sheet, i.e., it rested on the Barents Sea floor during the Last Glacial Maximum (21 ky BP). The Bjørnøyrenna Ice Stream was the largest ice stream draining the Barents Sea Ice Sheet and is regarded as an analogue for contemporary ice streams in West Antarctica. Here, the retreat of the Bjørnøyrenna Ice Stream is simulated by means of two numerical ice sheet models and results assessed against geological data. We investigate the sensitivity of the ice stream to changes in ocean temperature and the impact of grounding-line physics on ice stream retreat. Our results suggest that the role played by sub-shelf melting depends on how the grounding-line physics is represented in the models. When an analytic constraint on the ice flux across the grounding line is applied, the retreat of Bjørnøyrenna Ice Stream is primarily driven by internal ice dynamics rather than by oceanic forcing. This suggests that implementations of grounding-line physics need to be carefully assessed when evaluating and predicting the response of contemporary marine-based ice sheets and individual ice streams to ongoing and future ocean warming.

Highlights

The Barents Sea Ice Sheet was a marine-based ice sheet, i.e., it rested on the Barents Sea floor during the Last Glacial Maximum (21 ky BP)
In order to better establish the interplay between ocean warming, sea level and grounding-line physics in triggering the retreat of the Bjørnøyrenna Ice Stream, we focus on the evolution of its southern branch between 21–10 ky BP
We have presented transient numerical simulations of the last deglaciation of the Eurasian Ice Sheet Complex, carried out with two different Ice Sheet Models (ISMs)

Summary

Introduction

The Barents Sea Ice Sheet was a marine-based ice sheet, i.e., it rested on the Barents Sea floor during the Last Glacial Maximum (21 ky BP). Analytical and numerical studies suggest that an initial retreat of the grounding-line position can lead to abrupt changes in volume and extent of marine-based ice sheets in regions where the bedrock is sloping towards the interior of the ice sheet (i.e., retrograde slopes)[12,13,14]. We perform transient simulations with two ISMs, namely the GRenoble Ice Shelf and Land Ice model (GRISLI)[19] and the Stockholm Branch of Penn State University glacial model (PSU)[20], in order to investigate the role played by sub-shelf melting and grounding-line dynamics as triggers of the retreat of the Bjørnøyrenna Ice Stream after the LGM. The timing of the simulated retreat from Sentraldjupet is compared with deglacial chronologies derived from marine geological data[5,6] (Fig. 1)

Objectives

Methods

Results

Conclusion