Massive Ice Layer Formed by Refreezing of Ice-shelf Surface Melt Ponds: Larsen C Ice Shelf, Antarctica
Friday, 18 December 2015
Poster Hall (Moscone South)
Surface melt ponds now form frequently on ice shelves across the northern sector of the Antarctic Peninsula in response to regional warming and local föhn winds. Analysis of a new, 1-year set of observations from an Automatic Weather Station on Larsen C Ice Shelf, Antarctica, reveals that föhn winds are able to cause intense melt in summer, and even into the late austral autumn. A potentially important, but hitherto unknown, consequence of this intense surface melting and ponding is the formation of high-density near-surface ice from the refreezing of that water. We report the discovery of a massive subsurface ice layer located in an area of intense melting and intermittent ponding on Larsen C Ice Shelf, Antarctica. We combine borehole optical televiewer logging and ground-based radar measurements with remote sensing and firn modelling to investigate the formation and spatial extent of this layer, found to be tens of kilometres across and tens of metres deep. The presence of this ice layer has the effect of raising local ice shelf density by ~190 kg m-3 and temperature by 5 - 10 °C above values found in areas unaffected by ponding and hitherto used in models of ice-shelf fracture and flow.