Using gravimetry and meteorological data to assess the influence of El Niño-Southern Oscillation on Antarctica’s mass balance

Abstract

Given that the Antarctic Ice Sheet (AIS) has the potential to raise sea level by many tens of metres, it is crucial that we fully understand the factors controlling its mass balance and stability. Presently, much of the mass loss from the west AIS is being offset by accumulation over the East, such that the net AIS contribution to global mean sea level rise is not as great as it would otherwise be. This compensation is, however, sensitive to changing oceanic and atmospheric conditions including ocean warming, shifting winds and precipitation patterns. Previous research has shown that interannual variations in atmospheric conditions associated with El Niño-Southern Oscillation can alter surface-pressure distribution and moisture transport over Antarctica, potentially inducing mass balance changes over the ice sheet. This study makes use of the GRACE Mascons in combination with a range of auxiliary datasets, including atmospheric pressure, precipitation, sea surface temperature, and sea-ice, to investigate the relationship between El Niño and Antarctica’s surface mass balance. In particular, the mass balance signature and associated response of the ice sheet to the very strong 2015 El Niño are elucidated and set within the context of the historical record. Our results show that the 2015 El Niño resulted in opposite response to the long-term secular trend of the ice sheet, with an increase (decrease) in the West (East). Strong similarities in atmospheric conditions were found between very strong events, mainly the 1997-98 and 2015- 16, but little similarity was found with other previous events. We show that the Antarctic Peninsula and West Antarctica are particularly sensitive regions to El Niño variability, as well as Dronning Maud Land and Wilkes Land (East Antarctica). Overall, this study provides the first estimate of Antarctica’s surface mass balance following an extreme El Niño event using gravimetry and contributes to our understanding of Antarctica’s mass changes on interannual timescales.

Date of Award	6 Nov 2018
Original language	English
Awarding Institution	University of Bristol
Supervisor	Rory J Bingham (Supervisor)