West Antarctic Ice Sheet retreat in the context of ENSO variability

Satellite observations show rapid changes in the rate of ice loss from West Antarctica, but attribution of their cause is uncertain and requires modelling of the full ice-ocean system. Recent studies highlight the influence of El Niño Southern Oscillation (ENSO) on this important contribution to sea level. The hypothesised mechanism is through changes in ice-shelf melting, attributed to wind-forced variation in the depth of the oceanic thermocline that separates cooler surface waters from warmer Circumpolar Deep Water beneath. To improve upon detailed forecasts of West Antarctic ice using steady climate forcing, we propose novel experiments using a new synchronously coupled ice/ocean model that can continuously compute the response of the ice sheet to highly-variable oceanic forcing driven by ENSO. We seek to quantify: (1) the probability that 20th Century retreat of West Antarctic ice was triggered by ENSO; (2) the probability that sequential strong La Niña events could halt the retreat happening now; (3) formal attribution of changes in the West Antarctic Ice Sheet to ENSO or anthropogenic trends in zonal winds; and (4) the impact of ENSO and anthropogenic trends on predicted extremes of 21st Century sea level used for coastal planning decisions.

By reducing uncertainty around the interaction between oceans and ice sheets, and the future contribution of Antarctica to sea level rise, the proposed research will benefit:
1) The Environment Agency in management of the coastal environment.
2) Government departments, e.g. Treasury, BEIS, in making decisions about resource allocation.
3) Other partners in the UK RIDE forum in understanding the risks of climate change and assessing options for avoiding or managing such risks. See https://nerc.ukri.org/research/partnerships/ride/ for details of the RIDE forum.
4) Business and industry in making investment decisions about long-lived infrastructure projects.
5) Local Authorities in making planning decisions.
6) The general public in allowing them to make informed decisions about energy use, and in playing an active and informed role in debates about coastal management, climate change, and the allocation of resources by government.