ABSTRACT
We combined an ensemble of satellite altimetry, interferometry, and gravimetry data sets using common geographical regions, time intervals, and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of Earth's polar ice sheets. We find that there is good agreement between different satellite methods--especially in Greenland and West Antarctica--and that combining satellite data sets leads to greater certainty. Between 1992 and 2011, the ice sheets of Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula changed in mass by -142 ± 49, +14 ± 43, -65 ± 26, and -20 ± 14 gigatonnes year(-1), respectively. Since 1992, the polar ice sheets have contributed, on average, 0.59 ± 0.20 millimeter year(-1) to the rate of global sea-level rise.
Subject(s)
Climate Change , Ice Cover , Antarctic Regions , Geographic Information Systems , GreenlandABSTRACT
This brief paper has two purposes. First, we gauge developments in the study of the Antarctic ice sheet over the last seven years by comparing the contents of this issue with the volume produced from an American Geophysical Union meeting, held in September 1998, on the West Antarctic ice sheet. We focus on the uptake of satellite-based observation; ice-ocean interactions; ice streams as foci of change within the ice sheet; and the time scales on which the ice sheet is thought to operate. Second, we attempt to anticipate the future challenges that the study of the Antarctic ice sheet will present. We highlight the role of the upcoming International Polar Year in facilitating a better coverage of in situ climatic observations over the continent; the pressing need to understand the causes and consequences of the contemporary changes observed in the Amundsen Sea sector of West Antarctica; and the need for improved physics in predictive models of the ice sheet.
ABSTRACT
The existence of many subglacial lakes provides clear evidence for the widespread presence of water beneath the East Antarctic ice sheet, but the hydrology beneath this ice mass is poorly understood. Such knowledge is critical to understanding ice flow, basal water transfer to the ice margin, glacial landform development and subglacial lake habitats. Here we present ice-sheet surface elevation changes in central East Antarctica that we interpret to represent rapid discharge from a subglacial lake. Our observations indicate that during a period of 16 months, 1.8 km3 of water was transferred over 290 km to at least two other subglacial lakes. While viscous deformation of the ice roof above may moderate discharge, the intrinsic instability of such a system suggests that discharge events are a common mode of basal drainage. If large lakes, such as Lake Vostok or Lake Concordia, are pressurizing, it is possible that substantial discharges could reach the coast. Our observations conflict with expectations that subglacial lakes have long residence times and slow circulations, and we suggest that entire subglacial drainage basins may be flushed periodically. The rapid transfer of water between lakes would result in large-scale solute and microbe relocation, and drainage system contamination from in situ exploration is, therefore, a distinct risk.
