Satellite gravity and the mass balance of the antarctic ice sheet

• Published in: Journal of Glaciology
• Main Authors: Bentley, C. R., Wahr, J. M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1998
• Subjects: Earth-Surface Processes; Antarctic; The Antarctic; Antarc*; Antarctica; Ice Sheet; Journal of Glaciology
• Online Access: http://dx.doi.org/10.1017/s0022143000002549; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000002549

Abstract Changes in the Earth’s gravity field with time have important applications to a broad range of disciplines. Any process that involves a large enough horizontal redistribution of mass, either within the Earth or on or above its surface, is potentially detectable. In particular, when ice sheets grow or shrink, gravity changes as mass is redistributed in the solid earth and between the oceans and the ice sheets. The sources of global sea-level rise (about 2 mm a −1 over the last century) and in particular the contribution of the Antarctic ice sheet thereto are not well understood. Gravity measurements can help to diminish this uncertainty. The technology currently exists to measure gravity with high accuracy by a dual-satellite mission in which the distance between the satellites is precisely monitored. We estimate from recent studies that temporal changes in the gravity field as determined by a satellite gravity mission lasting 5 years at an orbital height of 400 km would be sensitive to changes in the overall mass of the Antarctic ice sheet to a precision corresponding to better than 0.01 mm a −1 of sea-level change. However, the effects of three other phenomena that could each produce a temporally varying gravity signal with characteristics comparable to that caused by a change in Antarctic ice—postglacial rebound, inter-annual variability in snowfall, and atmospheric pressure trends — also need to be evaluated. Postglacial rebound could be partly separated from ice-mass changes with the aid of global positioning system campaigns and numerical models of rebound that use improved determinations of mantle viscosity also provided by the gravity mission. Determination of inter-annual ice-mass changes will be aided by measurements of moisture-flux divergence around the perimeters of the ice sheets and direct observations of inter-annual changes by the gravity satellite itself. The removal of pressure effects over Antarctica will become more effective as the number of automatic weather stations in the ...