Substantially accelerated mass loss,extensive dynamic thinning on the periphery,and grounding line retreat in the Amundsen Sea Embayment,have amplified long-standing concerns about the instability of the Antarctic ice sheet.However,the evolution of the ice sheet and the underlying causes of the changes remain poorly understood due in part to incomplete observations.Here, we constructed ice flow maps for the years 2014 and 2015 at high resolution (100 m)，inferred from Landsat 8 images using feature tracking method.These maps were assembled from 10,690 scenes of displacement vectors inferred from more than 10,000 optical images acquired from December 2013 to March 2016.We also estimated the mass discharges of the Antarctic ice sheet in v2008，2014, and 2015 using the high-resolution ice flow maps，InSAR-derived ice flow map, and ice thickness data.An increased mass discharge (40±24 Gt yr-1) from East InIdian Ocean sector was found since -2008,likely due to unexpected widespread glacial acceleration in Wilkes Land, East Antarctica.Furthermore, the other five oceanic sectors did not show any significant changes, contrary to the long-standing belief that present-day accelerated mass loss is primarily occurring in West Antarctica and the Antarctic Peninsula.In addition, we integrated the ice sheet mass discharge data with new surface mass balance (SMB) data to estimate the Antarctic mass balance.The most significant change in mass balance also occurred in the East Indian Ocean sector between 2008 and 2015，reaching -40±50 Gt yr-1,the large uncertainty is caused mainly by the error in the SMB data.The newly discovered significant accelerated mass loss and speedup of ice shelves in Wilkes Land suggest the potential for abrupt and irreversible destabilization, in which the marine ice sheets on an inland-sloping bedrock would be adversely impacted by increasingly warmer temperature and warm ocean current intrusions.This destabilization would pose an unexpected threat of increased sea level rise.
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