| According to the prediction of the5th report of Intergovernmental Panel on Climate Change (IPCC), glacial ablation will be the major source of the global sea level rise (SLR) in the feature. In2003-2009, the global glacier mass balance rate was approximate-259±28Gt·a-1, equivalently0.71±0.08mm·a-1SLR rate. Under the background of global warming, glacier, as a sensitive factor for climatic change, plays an important role in the aspect of climatic change research, understanding the interaction mechanism between climate and glacier change. Glacier mass balance observation is the bridge to explore the glacier change and its climate response mechanism. The development of satellite altimetry technology provides a effective means to observe glacier change in wide-range and long time series. And it is possible to observe elevation change of glacier that located where the natural environment is bad that traditional method cannot play a role.Iceland, with various type of glacier, is an important study area due to its plentiful of glacier source and high-sensibility of climatic change. Few studies have been done to estimate glacier mass balance in Iceland with satellite altimetry techonology, therefore, this study selects the Icelandic largest four ice fields (Vatnajokull, Langjokull, Hofsjokull and Myrdalsjokull) as research subjects, obtains the elevation information of the ice fields using The Ocean Topography Experiment (TOPEX)/Poseidon (T/P) Geophysical Data Record (GDR) data and Envisat Radar Altimeter-2(RA-2) GDR data, and then, estimates the glacier mass balance rate of Icelandic glacier in1992-2010.The main research contents include:(1) Calculate the elevation difference between every elevation point and the reference elevation in every pass with collinear analysis method and surface gradient correction, then compose all points of each pass into a elevation difference sequence.(2) Calculate the robust linear regression and uncertainty of elevation change trend via the iterated weighted least squares method, then analyse the interannual variation features of elevation change trend.(3) Calculate the mean elevation change trend of every ice field via weighted average method, then estimate the glacier mass balance rate of every ice field.(4) Analyse the relationship between the glacier mass balance rate and climate factor based on weather station data and the environmental effect of glacier change.The main conclusions include:(1) The results demonstrate the feasibility of using satellite radar altimeter data to estimate glacier mass balance, especially the large ice sheet, ice field and so on. The satellite radar altimetry has great potential for glacier elevation change observation due to its ability of all-weather working.(2) The Icelandic glacier mass balance estimation results indicate that in1992-2010, the most of Icelandic glaciers were in a state of negative mass balance. In1992-2002, the rate was-5.32±2.34Gt·a-1, however, in2002-2010, this value reached to-10.96±5.98Gt·a-1. It means that, when the time went into the21st century, the recession of Icelandic glacier was more serious.(3) The negative mass balance rate of Vatnajokull, the largest ice field in Iceland, was highest, reached to-4.22±1.01Gt·a-1and-8.58±3.38Gt·a-1in the two date spans (1992-2002and2002-2010) respectively, and Langjokull was the most unstable ice field because of its high unit area negative mass balance rate (reached to-1.29±0.36Gt·a-1·10-3·km-2and-1.93±0.95Gt·a-1·10-3·km-2in the two date spans respectively).(4) The SLR rate reached0.015±0.006mm·a-1and0.030±0.017mm·a-1to in the two date spans respectively. According to the rate, the Icelandic glacier melt will cause approximate2.73mm SLR in the end of the21st century without considering the increase of the rate, however, if consider the increase of the rate, the SLR caused by Icelandic glacier melt will reached to approximate6.27mm.(5) The interannual variation of glacier elevation change trend had close relationship with local air temperature change. In1992-2002, the air temperature in Iceland was increased which was consistent with the observation of Icelandic glacier mass balance rate. The low unit area negative mass balance rate of Vatnajokull indicated that the larger glacier has the stronger affordability to response the changes of environment temperature.(6) The application of more precise satellite altimetry data will provide more effective and accurate meathods to observe global glacier mass balance, it will be important research direction in the future. Exploring the deep relationship between glacier mass balance and climatic changes combining more climate data will also an important content in the future. |
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