Changes in ice dynamics of Totten Glacier, East Antarctica in the past two decades

Abstract:

Totten Glacier, East Antarctica, a glacier that holds a 3.9 m sea level change equivalent, has thinned and lost mass for decades. Observed thinning by satellite altimeters is concentrated in areas of fast flow, hence is probably of dynamic origin. In this study, we derive time series of ice velocity from Landsat and interferometric (InSAR) data (ERS-1/2, RADARSAT-1, ALOS PALSAR, TanDEM/TerraSAR-X and COSMO-Skymed) for the past two decades. We find significant speed-up in ice velocity, especially in 2002-2007, followed by a period of slow decrease in 2010-2014. Comparing the results with RACMO2 surface mass balance suggests that the glacier mass balance was already negative in 1996 and became more negative into the 2000s. To examine the stability of the glacier, we develop high-resolution topographies of the ice surface and ice bottom using NASA Operation IceBridge data, TanDEM-X data, InSAR ice velocities and a mass conservation method. The results reveal a 1,500-2,300 m deep grounding zone that extends 15 km inland along two prominent side lobes grounded only 15-50 m above hydrostatic equilibrium, or ice plain. At the glacier center, we detect a 1-3±0.12 km retreat of the grounding line by comparing differential InSAR data acquired 17 years apart. The retreat is asymmetrical along the two lobes, but consistently indicates a total thinning of 12 m from 1996 to 2013. On the ice plain, the glacier is prone to rapid retreat around a region about 7 km long, but inland the bed elevation rises. Sustained thinning will cause further retreat and probably speed up, but will not be conducive to a marine- instability. The ultimate cause of the changes is not known, but probably of oceanic origin, with most changes taking place in 2002-2007.