Further summer speedup of Jakobshavn Isbræ

We have extended the record of flow speed on Jakobshavn Isbræ through the summer of 2013. These new data reveal large seasonal speedups, 30 to 50% larger than previous summers. At a point a few kilometres inland from the terminus, the mean annual speed for 2012 is nearly three times as large as that in the mid 1990s, while the peak summer speeds are more than a factor of 4 greater. These speeds were achieved as the glacier terminus retreated to the bottom of an overdeepened basin with a depth of ~ 1300 m below sea level. While retreat may slow slightly as the terminus retreats farther – to a moderate rise in the bed – it is likely to reach the deepest section of the trough within a few decades, at which point it should rapidly retreat to the shallower regions ~ 50 km farther upstream, potentially by the end of this century.