Volume and velocity changes at Mittivakkat Gletscher, southeast Greenland

We document changes for Mittivakkat Gletscher, the peripheral glacier in Greenland with the longest field-based observed mass-balance and surface velocity time series. Between 1986 and 2011, this glacier changed by -15% in mean ice thickness and -30% in volume. We attribute these changes to summer warming and lower winter snow accumulation. Vertical strain compensated for similar to 60% of the elevation change due to surface mass balance (SMB) in the lower part, and similar to 25% in the upper part. The annual mean ice surface velocity changed by -30%, which can be fully explained by the dynamic effect of ice thinning, within uncertainty. Mittivakkat Gletscher summer surface velocities were on average 50-60% above winter background values, and up to 160% higher during peak velocity events. Peak velocity events were accompanied by uplift of a few centimeters.