Improved Analysis of Grace Data Shows Ice Accumulation in Greenland and Lower Global Ice Loss than Previous Studies
Wu, Z., Heflin, M.B., Schotman, H., Vermeersen, B.L.A., Dong, D., Gross, R.S., Ivins, E.R., Moore, A.W., and Owen, S.E. 2010. Simultaneous estimation of global present-day water transport and glacial isostatic adjustment. Nature Geoscience 3: 642-646.
Previous studies have used an estimated GIA model to adjust for this effect; but these models are not independent of ice accumulation/loss rates. Wu et al. solve this problem by simultaneously estimating GIA and Present-Day Surface Mass Trend (PDMT) for the globe. They use three sources of data: GRACE data, Ocean Bottom Pressure data from the Jet Propulsion Laboratory, and the three-dimensional surface velocities (from GPS data) of a network of 664 globally-distributed sites, the goal being to obtain global surface maps of both GIA and PDMT with high accuracy.
The most prominent result of this analysis is a reduction by about a factor of two in the estimate of current rates of ice loss for Greenland and Antarctica compared to previous GRACE estimates based on the a priori GIA model, due partly to clear evidence for ice accumulation in the interior of Greenland (accompanied by ice loss around the margins of Greenland). Parts of West Antarctica also show rapid loss and others rapid gain of ice mass, while East Antarctica seems relatively stable. The current (2002-2008) global non-steric (not due to ocean warming and water expansion) sea level rise attributable to ice mass loss is estimated in the study to be only 0.54 mm/yr (about 2 inches per century). This suggests that almost none of the sea level rise is due to glacial ice loss, as is widely assumed.