Ice-shelf dynamics near the front of the Filchner-Ronne Ice Shelf, Antarctica, revealed by SAR interferometry

Fifteen synthetic aperture radar (SAR), images of the Ronne Ice Shelf (also referred to as the Filchner-Ronne Ice Shelf;, Antarctica, obtained by the European remote-sensing satellites ERS-1 and -2, are used to study ice-shel f dynamics near two ends of the iceberg-calving front. Interferograms const ructed from these SAR images are used to resolve the ice-shelf displacement along several directions in response to both ocean tide and long-term cree p flow. Tidal motion is separated from creep flow using differential interf erometry i.e. two or more interferograms in which fringe patterns common to all are predominantly associated with creep flow. Creep-flow velocities th us determined compare well with prior ice-shelf velocity surveys. Using the se data, we studied the influence of large-scale rifts, ice rises and coast al separation on the ice-shelf flow. Many of the large rifts that appeal to form the boundaries where tabular icebergs may eventually detach from the ice shelf are filled with a melange of sea ice, ice-shelf debris and wind-b lown snow. The interferograms show that this melange tends to deform cohere ntly in response to the ice-shelf flow and has sufficient strength to trap large tabular ice-shelf fragments for several decades before the fragments eventually become icebergs. In man) instances, the motion of the tabular fr agments is a rigid-body rotation about a vertical asis that is driven by ve locity shear within the melange. The mechanical role of the rift-filling me lange ma) be to bind tabular ice-shelf fragments to the main ice shelf befo re they calve. This suggests two possible mechanisms by which climate could influence tabular iceberg calving. First, spatial gradients in oceanic and atmospheric temperature ma) determine where the melange melts and, thus, t he location of the iceberg-calving margin. Second, melting or weakening of ice melange as a consequence of climate change could trigger a sudden or wi despread release of tabular icebergs and lead to rapid ice-shelf disintegra tion.