Towards a Regional
Ocean / Ice-Sheet / Atmosphere
modelling System

The largest uncertainty on the 21st century sea level rise is related to the Antarctic ice sheet, where dynamical ice discharge is projected to increase, being only partly compensated by the effect of increased snowfall. A very large part of the increased discharge will likely occur through Pine Island and Thwaites glaciers that have an ice-shelf termination in the Amundsen Sea. These glaciers may already be engaged in a dynamical instability triggered by increased melt beneath their ice shelves. The later results from the Amundsen Sea warming that is likely related to wind changes at both regional and global scales. Several significant feedbacks between atmosphere, ocean and glacier dynamics have been suggested in the literature.

Current Earth System Models built for climate projections have many biases in the Antarctic region, and they do not represent the ocean beneath ice shelves and the glacier dynamics. The capability of representing the ocean in static ice-shelf cavities has been introduced in a few ocean models recently. The ice-sheet models have also improved significantly over the last few years, and a few ice models are now able to capture the fast acceleration of glaciers with a marine termination. However, most of these models are still forced by an imposed and idealized melt rate beneath their ice shelves, which hides feedbacks and makes future projections overly uncertain. Concerning the atmosphere, only a few regional models designed for the polar environment are currently able to simulate the complex surface mass balance and coastal winds of Antarctica.

The TROIS-AS project aims to build a regional modeling system enabling the representation of physical processes and feedbacks at the ocean/ice-sheet and atmosphere/ice-sheet interfaces. The objective is to quantify the contribution of Pine Island and Thwaites glaciers to global sea level rise over the next 100 years. The project covers 2015-2019 and is conducted at the Institut de Géosciences de l’Environnement (IGE, Grenoble, France) and is funded by ANR. The PI of this project is Nicolas Jourdain, and the main investigators are Gaël Durand, Hubert Gallée, Julien Le Sommer, Nacho Merino, Marion Donat-Magnin, Olivier Gagliardini, Fabien Gillet-Chaulet, and Lionel Favier.