Multi-sensor remote sensing observations of the near past and present structure and dynamics of Wilkins Ice Shelf (Antarctic Peninsula)

The size of the Wilkins Ice Shelf, Antarctica, a thin ice shelf in the Bellinghausen Sea, has considerably declined in the past two decades and thus, it is of general interest to investigate its stability and recent changes. Furthermore, the Wilkins Ice Shelf (WIS) is currently right at the -9°C isotherm, where the limit of existence of ice shelves is proposed by various authors. In this study, we combine various remote sensing technologies and products to obtain an improved, interdisciplinary understanding of current of the structure and dynamics of the WIS. We document the retreat of the ice front of the WIS from 1986 to 2007, as well as the formation of cracks and extent of melt ponds by means of multi-spectral and SAR remote sensing imagery. A general analysis of ice shelf structures and their temporal changes is performed based on a Landsat mosaic from 19986/90 and a recent TERRA ASTER mosaic from 2001-06. Differential SAR interferometry (ERS-1/2 tandem and ice phase) was used to derive 2D flow fields for the south-eastern part of the ice shelf and its major tributary glaciers. The flow field of the floating ice is then interpreted in combination with the observed rift patterns in order to evaluate the general stress directions, with a focus on the grounded areas that generally act as pinning points and thus stabilize the ice shelf. This is subsidized by the fringe patterns of multiple interferograms. Both the multi-temporal optical imagery as well as an interferogram with a long temporal baseline show indications for changes in the dynamics of tributary glaciers. The freeboard height of the floating ice has been evaluated from ICESat surface elevation data from 2003-06. This data has been analysed in regard to tidal effects, crack formation and the variability of the hinge zone. Furthermore, the freeboard height was used to estimate the ice thickness, which was compared with radio echo sounding data from the early seventies. The multi-sensor and interdisciplinary approach provides a detailed view of the recent and near-past state of the ice shelf as well as indications for ongoing changes in ice dynamics. The data set provides a formidable base for subsequent ice shelf modelling.