Estimating the rates of mass change, ice volume change and snow volume change in Greenland from ICESat and GRACE data

Details Estimating the rates of mass change, ice volume change and snow volume change in Greenland from ICESat and GRACE data Estimating the rates of mass change, ice volume change and snow volume change in Greenland from ICESat and GRACE data

Jan 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009geoji.176...95s&link_type=abstract

Geophysical Journal International, Volume 176, Issue 5818, pp. 95-106.

Astronomy and Astrophysics

Astronomy

9

Sea Level Change, Time Variable Gravity, Glaciology, Arctic Region

Scientific paper

The focus of this paper is on the quantification of ongoing mass and volume changes over the Greenland ice sheet. For that purpose, we used elevation changes derived from the Ice, Cloud, and land Elevation Satellite (ICESat) laser altimetry mission and monthly variations of the Earth's gravity field as observed by the Gravity Recovery and Climate Experiment (GRACE) mission.
Based on a stand alone processing scheme of ICESat data, the most probable estimate of the mass change rate from 2003 February to 2007 April equals -139 +/- 68 Gtonyr-1. Here, we used a density of 600+/-300 kgm-3 to convert the estimated elevation change rate in the region above 2000m into a mass change rate. For the region below 2000m, we used a density of 900+/-300 kgm-3.
Based on GRACE gravity models from half 2002 to half 2007 as processed by CNES, CSR, DEOS and GFZ, the estimated mass change rate for the whole of Greenland ranges between -128 and -218Gtonyr-1.
Most GRACE solutions show much stronger mass losses as obtained with ICESat, which might be related to a local undersampling of the mass loss by ICESat and uncertainties in the used snow/ice densities.
To solve the problem of uncertainties in the snow and ice densities, two independent joint inversion concepts are proposed to profit from both GRACE and ICESat observations simultaneously. The first concept, developed to reduce the uncertainty of the mass change rate, estimates this rate in combination with an effective snow/ice density. However, it turns out that the uncertainties are not reduced, which is probably caused by the unrealistic assumption that the effective density is constant in space and time. The second concept is designed to convert GRACE and ICESat data into two totally new products: variations of ice volume and variations of snow volume separately. Such an approach is expected to lead to new insights in ongoing mass change processes over the Greenland ice sheet. Our results show for different GRACE solutions a snow volume change of -11 to 155km3yr-1 and an ice loss with a rate of -136 to -292km3yr-1.

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