Survey and Modelling of East Antarctica – SUMER

The method is based on an exhaustive study of the processes that underlie the specific dynamical behavior of these glaciers from field data collected over the test zone. Over this area, comprehensive measuremnts protocols (deformation rates, specific behaviour of the grounding line, time-dependent thickness changes, etc..) will lead to constraining data sets for ice flow models thereby allowing for good initialisation and/or validation for these models. The resulting comprehension of the physical processes as well as the upgraded models will later serve the purpose of a larger-scale modelling approach over the entire WAL sector. There, although less intensive field measurements (bottom and uppper ice topographies) will allow for reliable simulations.
Along with this field work, developpement and testing of ice flow models will be conducted with an amphasis on the grounding line dynamics and more generally on the stability of outlet glaciers. Indeed, under specific topographic conditions (inward downsloping bedrock) these glaciers develop an instability leading to potential large-scale collapses. These model improvements will make the most of the finite-element code ELMER-ICE, partly develpped and improved at the Laoratory of Glaciology which acquired an internationally recognized expertise in this specific domain.

- Good understanding of the physical processes that underlie the specific behaviour odf outlet glaciers from observing the test zone.

- Establishing maps of bottom and surface topographies of the ice

- Establishing of maps of surface velocities for the same area

- Computation of the ice flux to the ocean from the 2 previous maps and the positioning of the grounding line.

- Upgrading of ice flow models from field data over the test zone

- Accurate modelling of the dynamical behaviour of the test zone

- Extension of the local results to all glaciers within the WAL sector. Better prediction of the contribution of this latter to the world-wide sea level.

By the end of the project, our improved knowledge of the processes along with the capability of correctly reproducing them with appropriate and sophisticated models will allow for a major step forward in the modelling of coastal glaciers.

Therefore, several applications can be envisaged :

- More and more accurate simultions of the future sea level changes from the decadal to centenial time scale

- Assuming sophisticated coupling with both the ocean and the atmosphere (with corresponding models) , a more global approach can be conducted with even more physical solutions giving more credit to longer-trem predictions.

Data emerging from the first field season of the project (continous velocity field from the permanent network + specific deformation rates)

Built up of the web site for public access to the data :
astrolabe.osug.fr

Paper :
E. Le Meur , M. Sacchettini , S. Garambois , E. Berthier , A. S. Drouet , G. Durand , D. Young, J. S. Greenbaum , D. D. Blankenship , J. W. Holt , E. Rignot , J. Mouginot , Y. Gim , D. Kirchner , B. de Fleurian, O. Gagliardini, and F. Gillet-Chaulet :
Two independent methods for mapping the grounding line of an outlet glacier – example from the Astrolabe Glacier, Terre
´Adelie, Antarctica, The Cryosphere Discuss., 7, 3969-4014, 2013

A great acceleration of polar outlet glaciers and a substantial related increase of sea level contribution have been observed for a decade. If the diagnosis of the current ice-sheet imbalance is now well established for the Greenland and West Antarctic regions, the picture is not that clear in East Antarctica in general and in the Wilkes and Adélie Lands (WAL) in particular. Exhaustive surveys of the WAL would further be motivated by the recent observations in this region of dynamical thinning and of topographic configurations suggesting potential internal instabilities. Concomitant with our awareness of the increased contribution of ice sheets to sea level rise, it has become evident that the current ice flow models cannot be relied on to reproduce the observed acceleration, therefore precluding any reliable anticipation of the forthcoming behaviour of outlet glaciers. SUMER proposes to address both the lack of surveys and modelling limitations in the WAL.
In a synoptic approach, the surveys launched as part of SUMER will range from innovative measurements on a local scale on a benchmark glacier to extensive aerial and space remote surveys of the whole considered region. The current state of balance of the WAL will therefore be quantified together with the time evolution of the fastest changing glaciers in the region. In addition to observational duties, SUMER will strongly participate in further developing of a current state-of-the-art ice flow model. Observations and modelling advances will feed into each other all along the project with the objective to establish reliable projections of the WAL contribution to sea level rise for the two next centuries.