Basal melting and freezing under the Amery Ice Shelf, East Antarctica

The basal melting and freezing rates under the Amery Ice Shelf, East Antarctica, are evaluated, and their spatial distributions mapped. Ice velocity, surface elevation and accumulation rate datasets are employed in the analysis, along with a column-averaged ice density model. Our analysis shows that the total area of basal melting is 34 700 km(2), with a total annual melt of 62.5 +/- 9.3 Gt and an average melting rate of 1.8 +/- 0.3 m a(-1). Basal freezing mainly occurs in the northwestern part of the ice shelf, over a total area of 26 100 km(2) and with a maximum freezing rate of 2.4 +/- 0.4 m a(-1). The total marine ice that accretes to the ice-shelf base is estimated to be 16.2 +/- 2.4 Gt a(-1). Using a redefined grounding line and geometry of the Amery Ice Shelf, we estimate the net melt over the ice-shelf base is about 46.4 +/- 6.9 Gt a(-1), which is higher than previous modeling and oceanographic estimates. Net basal melting accounts for about half of the total ice-shelf mass loss, with the rest being from iceberg discharge. Our basal melting and freezing distribution map provides a scientific basis for quantitative analysis of ice-ocean interaction at the ice-shelf-ocean interface.