Ice sheet mass imbalance: key geodetic contributions to climate monitoring
Abstract
As recently as 1992, it was possible for one author to conclude that, as far as we knew, the Antarctic ice sheet could be anything from a 600 Gt/yr source to 600 Gt/yr sink of ocean mass, a contribution of anything between adding or subtracting 2 mm each year to eustatic sea level. Underlying this uncertainty was the great difficulty of establishing through ground based observations the difference between the mass accumulated on the sheet through snow-fall and that lost through flow to the ocean at the ice sheet margins. In addition, the division of the mass loss between iceberg calving and ice shelf melting was more or less unknown, although the implications for the buoyancy forcing of the ocean of the two mass losses is quite different. In the space of a decade, satellite radar altimetry, particularly the observations of the European ERS satellites, have transformed our understanding of a great proportion of the ice sheet. We now know that the interior of the East Antarctic ice sheet is in a state of mass balance. Taken as whole, the sheet appears to be in a state of balance to within about 150 Gt/yr, in keeping with geodetic and sea level evidence that indicates Antarctic mass balance over the past few thousand years. On the other hand, altimetry has revealed that the grounded ice streams and basins of the Amudsen and Bellinghausen Sea sectors of the West Antarctic ice sheet are thinning. In some cases, the thinning is large: in some cases the streams will be completely afloat in 500 years if the thinning continues unabated. This paper will review the achievements of the past decade in observing the mass imbalance of the Antarctic ice sheet, detailing both the scientific and technical achievements. It will also outline the remaining problems, and comment on how the future US ICESAT and European CryoSat satellite missions will contribute to closing the uncertainty associated with this largest of the Earth's ice sheets.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA....14608W