Author/Authors :
H. J. Zwally ، نويسنده , , M. B. Giovinetto ، نويسنده ,
Abstract :
Changes of mean annual net accumulation at the surface on the grounded ice sheets of East
Antarctica, West Antarctica and Greenland in response to variations in sea ice extent are estimated
using grid-point values 100 km apart. The data bases are assembled principally by bilinear interpolation
of remotely sensed brightness temperature (Nimbus-5 ESMR, Nimbus-7 SMMR), surface
temperature (Nimbus-7 THIR), and surface elevation (ERS-1 radar altimeter). These data, complemented
by field data where remotely sensed data are not available, are used in multivariate analyses
in which mean annual accumulation (derived from firn emissivity) is the dependent variable; the
independent variables are latitude, surface elevation, mean annual surface temperature, and mean
annual distance to open ocean (as a source of energy and moisture). The last 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 concentration. Stepwise
correlation analyses indicate that variations in sea ice extent of 50 km would lead to changes in
accumulation inversely of 4% on East Antarctica, 10% on West Antarctica, and 4% on Greenland.
These results are compared with those obtained in a previous study using visually interpolated
values from contoured compilations of field data; they substantiate the findings for the Antarctic ice
sheets ( 4% on East Antarctica, 9% in West Antarctica), and suggest a reduction by one half of
the probable change of accumulation on Greenland (from 8%). The results also suggest a reduction
of the combined contribution to sea level variability to 0.19 mm a1 (from 0.22 mm a1).