| Summary: | Large areas of multi-year and multi-decade sea ice occur to the east of the Mertz Glacier Tongue (MGT) in East Antarctica. Measurements of the free-board height of this ice obtained by satellite-borne laser and radar altimeters indicates that the ice is many metres thick and in places tens of metres thick. Visual observations from ships of the above water layers of thick floes from the region suggest that the free-board is composed of snow. Snow accumulation rate for the region is estimated at around 1 m a1 from firn core data retrieved from the large iceberg B09B when it was grounded to the east of MGT. So the primary process contributing to the large thickness of the floes appears to be accumulation of snow at the surface and flooding to create snow-ice. The thick ice in the region has been described as landfast, however long fractures do form through the ice-field and allow the ice to diverge somewhat and move. But, the ice floes typically remain in place. They converge again, and export of ice appears to occur rarely. Re-location of iceberg B09B and calving of MGT in early 2010 brought about major changes. Large sections broke-up and drifted out to the west through what was the location of the Mertz Glacier polynya. The breakup and melting of the snow cover introduced a fresh-water pulse into the upper layers of the ocean in the region. We derive the temporal evolution of the spatial distribution of this thick ice and its growth through analysis of time series of SAR images and altimeter data from ICESat and CryoSat-2.
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