Sensitivity analysis of ice dynamics to climate forcing scenarios in David Glacier, East Antarctica

Abstract

As global mean temperature rises, there has been a growing interest in how much sea level would rise occurred due to polar glacial discharge to ocean. Currently, West Antarctica has been spotlighted due to ice discharge from the glaciers, compared to sea level contribution in East Antarctic glaciers. Bed elevation at East Antarctica is largely lying above sea level, which is likely to stable compared to West Antarctica. However, East Antarctic regions contain 10 times large sea level rise potential than West Antarctica. David Glacier, located in East Antarctica, is a region of fjord-like valley glacier, and ice drains into ocean through Drygalski Ice Tongue, which of length is about 80 km. To understand what mechanism modulates sea level rise, it is necessary to identify key factors affecting the acceleration of mass discharge in David glacier. Based on current knowledge, ice shelf buttressing effect, basal melting, and SMB (surface mass balance) are the components that have been known to affect glacier speed. Here, 2D Shallow Shelf Approximation model of the Ice Sheet System Model was used to predict response of glacier velocity distribution and contribution of sea level equivalent change depending on various forcing scenarios. Firstly, friction coefficient beneath glacier and ice rigidity on floating ice were estimated through inversion method, which constructed the initial condition of the regional model. Then, changing SMB, floating ice melting rate, and ice front position retreat could alter the sea level rise contribution and ice velocity. In the results, basal drag stress obtained through inversion method was largely calculated in the ice fall area where the subglacial ridge existed. Sea level equivalent for control model was -2.0 mm equivalent to ice mass gain of 15 Gt/yr during 50 years, and relatively stable than other fast flow regions, such as Pine Island Glacier. Ice front retreat over threshold, which was about 90 km from ice front, accelerated the ice velocity near grounding line larger than twofold floating ice melting rate. This ice velocity acceleration influenced increase in sea level equivalent of -1.95 mm in case of furthermost ice front retreat. However, ice tongue and 8 km region of ice shelf position did not affect the ice velocity acceleration.