Axis 2 - Evolution of glaciers and ice sheets

Context and objectives

The objective is to improve the understanding and quantification of the past, present and future evolution of glaciers and ice sheets in their changing environment. This objective responds to important societal issues because glacial dynamics induce specific natural risks (serac falls, water pockets, ...) and represents a significant source of uncertainty in the mass balance of glaciers and ice sheets with consequences in terms of sea level and water resources. We are working on a better characterization of the spatial and temporal variability of glacial dynamics, in the context of natural and forced climate variability. We are also working on the identification of tipping points that may induce self-sustained glacial retreats (instabilities), as well as on the estimation of uncertainties related to the use of multiple modelling tools.

Scientific strategy

Improving predictions of glacier and ice sheet mass changes requires better observing the ice dynamics (flow, geometry) at the scale of entire glaciers and ice sheets. This is possible today thanks to the growing amount of remote sensing data, e.g. obtained through new generations of sensors such as the Sentinel program (Copernicus, ESA). The design of future space missions (NISAR-NASA, Earth Explorer 10-ESA) also requires our expertise to anticipate .

By assimilating these observations in our modeling chains, in particular for historical simulations, we aim to better quantify the contribution of ice dynamics to the ice mass changes in response to ocean/atmosphere variations, and to reduce the various sources of uncertainty (ice thickness distribution, parameterizations, initial state).

We also refine the reconstructions and projections of ice mass variations by including the processes mentioned in axis 1, and by better representing the ice interactions with the ocean and the atmosphere. Estimating the feedbacks with other components of the climate system motivates the inclusion of ice sheet dynamics in national Earth system models.

Tools and Methods

We improve satellite data processing methodologies (image correlation, interferometry, lidar measurements). These new observations directly contribute to a better assessment of the evolution of ice sheets and glaciers over the past decades, in particular the ice flows coming out of the ice sheets.

The chain from the process to the large scale is addressed in a single modelling tool (Elmer/Ice), which allows to estimate the propagation of uncertainties. Given the increasing duration of observational time series, we are working on the development of transient assimilation methods, particularly with ensemble methods. Finally, we are promoting the use of Elmer/Ice in a larger climate community, and are coupling Elmer/Ice to other components of the climate system (NEMO, LMDz and MAR).

Finally, studies on glaciers have strong local stakes, they require a close collaboration with IGE’s C2H team for the climate and surface mass balance aspects and will be done in connection with local actors (municipalities, hydro-electric companies, ...).