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ABSTRACT. We calculate the present ice budget for Antarctica from measurements of accumulation minus iceberg calving, run-ofT and in situ meltin~ beneath the floating ice shelves . The resulting negative mass balance of 469 Gt yeardifTers substantially from other recent estimates but some components are subject to high temporal variability and budget uncertainties of20-50%. Annual accumulation from an earlier review is adjusted to include the Antarctic Peninsula for a total of 2144Gtyear-l . An iceberg production rate of 2016 Gtyear-I is obtained from the volume of large icebergs calculated from satellite images since 1978, and from the results of an international iceberg census project. Ice-shelf melting of 544 Gt year-I is derived from physical and geochemical observations of meltwater outflow, glaciological field studies and modeling of the sub-ice ocean circulation. The highest melt rates occur near ice fronts and deep within sub-ice cavities. Run-ofT from the ice-sheet surface and from beneath the grounded ice is taken to be 53 Gt year-I. Less than half of the negative mass balance need come from the grounded ice to account for the unattributed 0.45 mm year-I in the IPCC "best estimate" of the recent global sea-level rise.

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