Surface elevation change has been investigated using merged radar altimeter measurements from the European Space Agency (ESA) satellites ERS-1, ERS-2 and Envisat for the period of 1992-2007. In addition, accumulation variations from different model simulation on the Greenland Ice Sheet (GrIS), as well as atmospheric teleconnections in the Northern Hemisphere during winter time, which are related to the surface mass balance of GrIS, have been analyzed. The results about the possible mass changes of GrIS under the background of Global Warming and the possible reason for that are shown below.
(1) Surface elevation change is identified through analysis of data from satellite-borne rader altimeters, and it is found that during the 1992-2007 period, the elevation change rate ( dH dt ) is about 3.8±0.2 cm per year,which means the mass of GrIS is increasing.
However, the difference of dH dt have been noticed between the yeas 1992-2007 and the years 2003-2007. During the first period, the dH dt is about 3.9±0.2 cm per year, while during the second period, the dH dt is about -0.6±0.4 cm per year, which shows
the increasing and decreasing of the GrIS mass during the two periods. This decadal change is even clearer if we investigate the surface elevation change of high elevation area and low elevation area, respectively.
(2) The decadal changes of accumulation, both temporal and spatial, on GrIS have been analyzed by comparing accumulation data from different model simulation. It is indicated that the accumulation during the 1992-2002 period slightly increased, whereas the accumulation significantly decreased during the 2003-2007 period. Therefore, it is suggested that the changes of the surface elevation during this two periods attributed primarily to accumulation variability.
(3) The variability of accumulation on GrIS is closely related to atmospheric circulation patterns. The analysis of the relationship between the changes of surface elevation of GrIS and sea level pressure implied that both the North Atlantic Oscillation (NAO) and the North Pacific Oscillation (NPO), significantly influence the GrIS winter elevation change by influencing the accumulation on GrIS.
Further, it is suggested that NAO may affect the accumulation over the western part of Greenland by influencing the storm activity and the moisture transport to this part, while the NPO may impact the accumulation over the northwestern, middle and the southeastern part of Greenland by influencing the storm activity and the moisture transport to these regions.