Ice Shelf Area and Ice Shelf Area Change from Sentinel-1 SAR and Cryosat-2 Altimetry Data

Abstract

Floating ice shelves fringe 74% of Antarctica's coastline, providing a direct link between the ice sheet and the surrounding oceans. A better understanding of Antarctic ice shelves and the physical processes affecting them has been the main objective of ESA’s Polar+ Ice Shelves project. The study’s main objective has been the advance in the use satellite observations and modelling to a better understanding of Antarctic ice shelves and the physical processes affecting them. A suite of geophysical products based on Earth Observation datasets from the last decade and modelling has been defined and produced over selected target ice shelves in Antarctica. One of these products, the ice shelf area change, is an important indicator of ice shelf stability in a warming climate, being affected by grounding line retreat as a possible consequence of ice thinning and calving events including ice shelf disintegration or collapse. An ice shelf is bounded at its seaward margin by the calving front while its inland border to the grounded ice of the Antarctic continent is given by the grounding line. Our calving front location is derived from Cryosat-2 swath elevation, while the grounding line is detected as the upper limit of ice shelf tidal flexure from Sentinel-1 and, prior to 2015, ERS-1/2 interferometric data. Time series of individual grounding lines from Sentinel-1 SAR triplets acquired at various dates within the ocean tide cycle have been processed and averaged over one entire year in order to obtain a gapless yearly grounding line. Eventually, time series of complete ice shelf delineations are obtained from the combination of these two products. It is possible to track absolute and relative area change of an ice shelf and additionally to partition the change into the individual contributions induced by the calving front and grounding-line migration. The annual ice shelf perimeters of the Amery Ice Shelf from 2011 to 2020 is visualized in the attached Figure 1. More similar examples over major ice shelves will be shown at the workshop.