Greenland Ice Sheet Mass Loss from GRACE Monthly Models
The Greenland ice sheet is currently experiencing a net mass loss. There are however large discrepancies between the published qualitative mass loss estimates, based on different data sets and methods. There are even large differences between the results
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Greenland Ice Sheet Mass Loss from GRACE Monthly Models L. Sandberg Sørensen and R. Forsberg
Abstract The Greenland ice sheet is currently experiencing a net mass loss. There are however large discrepancies between the published qualitative mass loss estimates, based on different data sets and methods. There are even large differences between the results based on the same data sources, as is the case with those estimated from GRACE data. In this chapter we have used a generalized inversion method to estimate the Greenland ice sheet mass change from the monthly global gravity solutions, provided by three different GRACE processing centers; CSR, JPL and GFZ. In order to derive mass change from these monthly global gravity models, we first calculate the gravity trend from these. When isolating the gravity trend signal, which is caused by the ice mass change, we first subtract the signal produced by the postglacial rebound (PGR) in Greenland. This is done by a simple method based on the ice history model ICE-5G and on ground measurements made in Scandinavia. We find that the PGR signal corresponds to a mass change signal of approximately –4 Gt per year. We conclude that there are large differences between these estimated mass change models. We find a total mass loss of 189, 146 and 67 Gt/year based on the CSR, GFZ and JPL solution respectively.
70.1 Introduction The Greenland ice sheet mass change is currently a hot topic. The IPCC report from 2007 stated that the response of the Greenland ice sheet to the observed climate changes is very poorly understood (Solomon et al., 2007). Much research has been done in order to improve our knowledge of the ice sheet, and in particular in estimating the mass loss of the ice sheet and hence the resulting sea level rise. In recent years, many research groups have published Greenland ice sheet mass loss estimates, based on different data sets and methods (Chen et al., 2006; Rignot and Kanagaratnam, 2006; Veligcogna and Wahr, 2006; Luthcke et al., 2006). It is clear though, that there is poor agreement between these estimates, which indicates that there are large differences in the way to handle the data. Even published results based on data solely from the Gravity Recovery and Climate Experiment (GRACE) are not all in agreement (Velicogna and Wahr, 2006; Luthcke et al., 2006; Wouters et al., 2008). Some of the published GRACE mass change estimates are listed in Table 70.1.
Table 70.1 Ice mass change estimates of the Greenland Ice Sheet by different authors, using different GRACE data time spans and methods Authors Time span Mass change L.S. Sørensen () Department of Geodynamics, National Space Institute, DTU-Space, Copenhagen Ø DK-2100, Denmark e-mail: [email protected]
Chen et al. (2006) Luthcke et al. (2006) Velicogna and Wahr (2006) Wouters et al. (2008)
2002–2005 2003–2005 2002–2006 2003–2008
S.P. Mertikas (ed.), Gravity, Geoid and Earth Observation, International Association of Geodesy Symposia 135, DOI 10.1007/978-3-642-10634-7_70, © Springer-Verlag Berlin Heidelberg 2
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