Volume loss of the Greenland ice sheet revealed by SARAL/AltiKa repeat passes radar altimetry

摘要

The Greenland ice sheet (GrIS) is one of the drivers of global sea level rise and plays a crucial role in understanding the global climate changes. Here, we have estimated and analysed the decadal (between 2013a??2016 and 2003a??2005) and annual (2014a??2015, 2015a??2016) volume discharge of ice from the entire GrIS. The 40 Hz Geophysical Data Record product of the unique Ka band (AltiKa) radar altimeter were utilised to derive the elevation, elevation changes and volume changes over the GrIS. To test the first-level accuracy of the result, AltiKa and NASAa??s ice, cloud and land elevation satellite digital elevation model (ICESat DEM)-derived elevation were compared, which yielded a correlation value of 0.95. Thereafter, decadal volume changes obtained over the entire GrIS, from the differencing of the AltiKa and ICESat DEM elevation revealed a decreasing rate of 247 km$^{3}$/year. Moreover, basin-wise analysis indicated the maximum decrease in elevation of basin located in the north and north-west region of GrIS. Annual changes obtained by differencing the AltiKa cycle of the same month (so that the surface condition will remain same) between the two consecutive years, specifically during 2014a??2015 and 2015a??2016 over the entire GrIS contributed volume loss of 187 and 210 km$^{3}$, respectively, indicating an enhanced decrease for a later period.