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The Sentinel-1 acquisition planning for polar regions provides almost uninterrupted observations of the Greenland Ice Sheet margin, key regions in Antarctica and other polar ice masses. The satellite constellation has thereby changed the landscape for satellite Earth observation (EO) in the polar regions, providing excellent opportunities for operational monitoring of key climate variables including ice velocity and glacier discharge. Based on Sentinel-1 SAR imagery, an archive of ice velocity maps covering the polar regions has been generated, encompassing the entire mission duration. The ice velocity maps, complemented with ice thickness and other EO datasets, form the basis for deriving ice flow, discharge fluctuations and trends at sub-monthly to multi-annual time scales, providing key input for ice dynamic and climate modelling. Our results underscore the value of long-term comprehensive monitoring of the polar ice masses, which is vital to gain insight for predicting their response to ongoing climate and ocean warming.

We use repeat-pass SAR data to produce detailed maps of surface motion covering the glaciers draining into the former Larsen B ice shelf, Antarctic Peninsula, for different epochs between 1995 and 2013. We combine the velocity maps with estimates of ice thickness to analyze fluctuations of ice discharge. The collapse of the central and northern sections of the ice shelf in 2002 led to a near-immediate acceleration of tributary glaciers as well as of the remnant ice shelf in Scar Inlet. Velocities of the glaciers discharging directly into the ocean remain to date well above the velocities of the pre-collapse period. The response of individual glaciers differs and velocities show significant temporal fluctuations, implying major variations in ice discharge and mass balance as well. Due to reduced velocity and ice thickness the ice discharge of Crane Glacier decreased from 5.02 Gt a−1 in 2007 to 1.72 Gt a−1 in 2013, whereas Hektoria and Green glaciers continue to show large temporal fluctuations in response to successive stages of frontal retreat. The velocity on Scar Inlet ice shelf increased two- to three fold since 1995, with the largest increase in the first years after the break-up of the main section of Larsen B. Flask and Leppard glaciers, the largest tributaries to Scar Inlet ice shelf, accelerated. In 2013 their discharge was 38%, respectively 45%, higher than in 1995.

Observations of the 3D ice velocity field are important for studies of glacier hydraulics and for modeling the dynamic response of glaciers to changing boundary conditions. A method for 3D ice velocity retrieval from repeat pass SAR data of crossing orbits applying offset tracking in amplitude images is presented. In contrast to the conventional technique for ice motion mapping which assumes surface-parallel flow, this method delivers the true velocity vector. The procedure is validated using in-situ GPS data on an outlet glacier of the Vatnajokull ice cap in Iceland.