Estimating Antarctic ice sheet mass balance from gravimetry and altimetry

• Main Author: Meister, R.
• Published: University College London (University of London) 2012
• Subjects: 550
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.625920

Estimates of the Antarctic ice sheet mass balance from the past ten years show great discrepancy. Deriving mass values from gravity measurements is a ffected by corrections for postglacial rebound (PGR). Calculating Antarctic ice sheet mass balance from altimetry satellites requires knowledge of surface densities. Here, two instruments were used in conjunction to constrain ice sheet mass balance. Surface height trends from the Envisat radar altimeter and mass trends from GRACE were analysed for the period January 2003 until October 2010. An analysis of errors related to GRACE gravity measurements was carried out and a best method for removal of errors was chosen. Envisat altimetry corrections were examined. Envisat surface height trends were converted into units of mass and smoothed with a 300km Gaussian filter in order to be compatible with the GRACE mass trend. This was done using a) the density of ice (917kg=m3), b) a firn density of 450kg=m3 and c) a variable surface density map of the Antarctic derived from observations of changes in the pattern of surface height trends. Subtracting the altimetry mass trend from the GRACE mass trend provides results dominated by the absence of altimetry data in the Antarctic peninsula and south of 81:6 degrees south. Therefore, ICESat altimetry trend values were added to the Envisat trend map, where available. The GRACE mass trend and the smoothed altimetry trend converted to mass show very good agreement. The diff erence between GRACE and the combined Envisat-ICESat altimetry trends can be interpreted as a combination of PGR and error. Integrating this di fference provides considerably smaller PGR values than all commonly used PGR models. The integrated area trends from both gravimetry and altimetry show mass loss for West Antarctica, mass gain for East Antarctica and an acceleration of melting in the Amundsen Sea Sector.