Elmer/Ice-Sheet: a dedicated model for fast changing ice sheets – EIS

Ice sheets are the main contributor to long-term sea-level changes. Since the mid-nineties, the observation of unexpected, important and rapid dynamical changes of numerous outlet glaciers shed light on the vulnerability of our society to sea-level rise. As pointed out in the last two IPCC assessment reports the main uncertainty in the projections of future sea-level rise stands in our so far poor ability to model the coastal dynamics of ice sheets. In particular, potential collapse of marine based sectors in Antarctica (the so-called Marine Ice Sheet Instability), if initiated, could cause global mean sea level to rise substantially above the likely range during the 21st century.
The technical objective of this project is to boost the on-going developments of the new-generation ice sheet model Elmer/Ice-Sheet, with unprecedented capacities in modelling coastal ice-sheet dynamics, and spread its use among the national and international climate community. Such developments are needed to tackle longstanding questions related to both past and future rapid changes of ice sheets. In particular, they will improve our ability to establish reliable projections of forthcoming evolution of ice sheets, their related contribution to sea-level rise and the feedbacks on other components of the climate system.
To achieve this objective, we will simulate (i) the deglaciation of the former Barents-Kara ice sheet, a paleo-analogue of present-day West Antarctica, and (ii) the evolution of Greenland and Antarctica during the Eemien period (127-115 ka BP), during which the sea level was 5 to 10 m higher than presently. This will shed light on the processes involved in the collapse of marine ice sheet and better constrain our projections of the evolution of the Antarctic mass balance for the next centuries. The Elmer/Ice-Sheet model will also be used to reanalyse the collapse of the Larsen B ice shelf that took place in 2002, before considering the evolution of the Larsen C one, whose front regularly retreats and which could soon suffer the same fate as his neighbour. These analyses of ice shelf collapses will provide a more accurate estimate of the maximum sea-level contribution that could result from a rapid retreat of Antarctic glaciers and subsequent impact on the climate system. We will further design, and propose to the international community, a regional coupled ocean – ice sheet model benchmark of the most vulnerable region of Antarctica, the Amundsen Sea sector. This will prepare the implementation of Elmer/Ice-sheet within the CNRM-CM and IPSL-CM Earth System Models and offer to the national community ESMs with state-of-the-art representation of dynamical ice sheets ready for CMIP7.