ANNUAL SEA-LEVEL VARIABILITY INDUCED BY CHANGES IN SEA-ICE EXTENT ANDACCUMULATION ON ICE SHEETS - AN ASSESSMENT BASED ON REMOTELY-SENSED DATA

Changes of mean annual net accumulation at the surface on the grounded ice sheets of East Antarctica, West Antarctica and Greenland in respo nse to variations in sea ice extent are estimated using grid-point val ues 100 km apart. The data bases are assembled principally by bilinear interpolation of remotely sensed brightness temperature (Nimbus-5 ESM R, Nimbus-7 SMMR), surface temperature (Nimbus-7 THIR), and surface el evation (ERS-1 radar altimeter). These data, complemented by field dat a where remotely sensed data are not available, are used in multivaria te analyses in which mean annual accumulation (derived from firn emiss ivity) is the dependent variable; the independent variables are latitu de, surface elevation, mean annual surface temperature, and mean annua l distance to open ocean (as a source of energy and moisture). The las t is the shortest distance measured between a grid point and the mean annual position of the 10% sea ice concentration boundary, and is used as an index of changes in sea ice extent as well as of mean concentra tion. Stepwise correlation analyses indicate that variations in sea ic e extent of +/-50 km would lead to changes in accumulation inversely o f +/-4% on East Antarctica, +/-10% on West Antarctica, and +/-4% on Gr eenland. These results are compared with those obtained in a previous study using visually interpolated values from contoured compilations o f field data; they substantiate the findings for the Antarctic ice she ets (+/-4% on East Antarctica, +/-9% in West Antarctica), and suggest a reduction by one half of the probable change of accumulation on Gree nland (from +/-8%). The results also suggest a reduction of the combin ed contribution to sea level variability to +/-0.19 mm a(-1) (from +/- 0.22 mm a(-1)).