Diurnal variation of GEC parameters during pre-blizzard conditions. Glaciological Studies in Schirmarchar Glacier using Global Positioning Systems (GPS)
Antarctica, which contains 90% of the world’s total ice, has an active role in global climate change. As Antarctica is covered by thick glaciers that grow by continuous snowfall/snowdrift, the surface velocity and strain field of the glaciers, through which most of the continents ice is discharged to the coast, can provide useful information on phenomena such as glacier surges and the effect of global warming. To facilitate these studies, critical areas of the outlet regions, are required to be monitored. Schirmarchar Glacier is one such important outlet glaciers in central Dronning Maud Land (cDML), playing a major role in contributing to the drainage of coastal region in East Antarctica. Three GPS campaigns were made during the summers of 2003, 2004 and 2005. GPS data collected at 21 sites in 2003 and 2004 have been analyzed to estimate the site coordinates baselines and velocities in a consistent International Terrestrial Reference Frame (ITRF2000). All the GPS points in the glacier and the rocky base station t Maitri have been constrained with the nearby International GNSS Service (IGS) stations VESL and SYOG. The horizontal velocities with respect to ITRF2000, are found to lie between 2 m yr-1 to 11 myr-1. The velocity gradient map prepared from the station velocities show the trend of the glacier flow towards the NNE direction with average velocity of 6.2 m yr-1 and enters to the Nivilsen shelf ice. The principal strain rates computed from the velocity gradient provide a quantitative measurement of the extension rates from 0.105 ± 0.01 x 103 yr-1 to 1.477 ± 0.85 x 103 yr-1 and the shortening rates from 0.044 ± 0.01 x 103 yr-1 to 0.963 ± 0.16 x 103 yr-1 . The velocity and strain distribution across the GPS network spatially aorrelates to the surface undulation gradients, crevasses and blockages of Nunataks and Schirmarchar Oasis.