A mass balance study of the West Antarctic ice sheet.

摘要

The present state of the West Antarctic ice sheet (WAIS) is a prime concern of science, but its large size and remote location have limited the amount of reliable data that are available for mass balance calculations. The spatial pattern of mass balance for a 100-km2 portion of the WAIS is estimated by calculating the residual flux of ice through 1-km grid cells organized into a geographical information system (GIS). The input data used for this estimate include continent-scale compilations of ice thickness and snow accumulation rate measurements, and ground-based measurements of snow accumulation rate and ice velocity. The calculation was performed using different combinations of input data so that error sources could be identified. The largest sources of error were associated with the continent-scale compilations of accumulation rate and ice thickness. These errors are greatly reduced when using snow accumulation rates derived from ground-penetrating radar (GPR) surveys. The best results, which agree with two previous estimates, suggest that this area is nearly in balance. Results also indicate that the mass balance varies within this 100-km2 grid. In some portions of the grid, local variations in mass balance correspond with measured changes in ice velocity and snow accumulation rate. In other parts of the grid, the apparent spatial variability is attributed to errors in the ice thickness data.; The results show that the demonstrated accuracy and spatial resolution of this high-resolution sampling approach are needed to understand the response of the entire West Antarctic ice sheet to recent changes in climate. However, the accuracy of the data compilations discussed above are examined using continuous, simultaneously recorded, ground-based measurements of ice-sheet surface topography, ice thickness, and snow accumulation rate that extend for hundreds of km beyond the grid at Byrd Station. Results from these analyses suggest that each of the compilations have larger errors than previously reported and therefore need to be improved before they are incorporated into estimates of WAIS mass balance.