Brief Communication: Further summer speedup of Jakobshavn Isbræ

We have extended the record of flow speed on Jakobshavn Isbrae through the summer of 2013. These new data reveal large seasonal speedups, 30 to 50% greater than previous summers. At a point a few kilometres inland from the terminus, the mean annual speed for 2012 is nearly three times as great as that in the mid-1990s, while the peak summer speeds are more than a factor of four greater. These speeds were achieved as the glacier terminus appears to have retreated to the bottom of an over-deepened basin with a depth of ~ 1300 m below sea level. The terminus is likely to reach the deepest section of the trough within a few decades, after which it could rapidly retreat to the shallower regions ~ 50 km farther upstream, potentially by the end of this century.

[1]  R. Forsberg,et al.  Step‐wise changes in glacier flow speed coincide with calving and glacial earthquakes at Helheim Glacier, Greenland , 2008 .

[2]  M. Lüthi,et al.  Ice mélange dynamics and implications for terminus stability, Jakobshavn Isbræ, Greenland , 2010 .

[3]  Jilu Li,et al.  Mapping of Ice Sheet Deep Layers and Fast Outlet Glaciers with Multi-Channel-High-Sensitivity Radar , 2009 .

[4]  Robert N. Swift,et al.  Accelerating ice loss from the fastest Greenland and Antarctic glaciers , 2011 .

[5]  Eric Rignot,et al.  A Reconciled Estimate of Ice-Sheet Mass Balance , 2012, Science.

[6]  Ian M. Howat,et al.  Large-scale changes in Greenland outlet glacier dynamics triggered at the terminus. , 2009 .

[7]  Ian M. Howat,et al.  Mass balance of Greenland's three largest outlet glaciers, 2000–2010 , 2011 .

[8]  I. Joughin,et al.  21st-Century Evolution of Greenland Outlet Glacier Velocities , 2011, Science.

[9]  Ian M. Howat,et al.  Submarine melting of the 1985 Jakobshavn Isbræ floating tongue and the triggering of the current retreat , 2009 .

[10]  Ian M. Howat,et al.  Synchronous retreat and acceleration of southeast Greenland outlet glaciers 2000–06: ice dynamics and coupling to climate , 2008 .

[11]  E. Rignot,et al.  Changes in the Velocity Structure of the Greenland Ice Sheet , 2006, Science.

[12]  Ian M. Howat,et al.  A new bed elevation dataset for Greenland , 2012 .

[13]  Robert N. Swift,et al.  Greenland Ice Sheet: Increased coastal thinning , 2004 .

[14]  Eric Rignot,et al.  A Reconciled Estimate of Ice-Sheet Mass Balance , 2012, Science.

[15]  Ian M. Howat,et al.  Seasonal to decadal scale variations in the surface velocity of Jakobshavn Isbrae, Greenland: Observation and model-based analysis , 2012 .

[16]  Ian Joughin,et al.  Large fluctuations in speed on Greenland's Jakobshavn Isbræ glacier , 2004, Nature.

[17]  Ian Joughin,et al.  Ice-Sheet Response to Oceanic Forcing , 2012, Science.

[18]  M. R. van den Broeke,et al.  Partitioning Recent Greenland Mass Loss , 2009, Science.

[19]  Konrad Steffen,et al.  Investigation of surface melting and dynamic thinning on Jakobshavn Isbrae, Greenland , 2003 .

[20]  Ian M. Howat,et al.  Continued evolution of Jakobshavn Isbrae following its rapid speedup , 2008 .

[21]  R. Thomas,et al.  Force-perturbation analysis of recent thinning and acceleration of Jakobshavn Isbræ, Greenland , 2004, Journal of Glaciology.

[22]  I. Joughin,et al.  Further summer speedup of Jakobshavn Isbræ , 2013 .

[23]  W. Harrison,et al.  Jakobshavns Isbræ, West Greenland: seasonal variations in velocity -- or lack thereof , 1990 .

[24]  Ian Joughin,et al.  Ice-sheet velocity mapping: a combined interferometric and speckle-tracking approach , 2002, Annals of Glaciology.

[25]  J. Weertman,et al.  Stability of the Junction of an Ice Sheet and an Ice Shelf , 1974, Journal of Glaciology.

[26]  W. T. Pfeffer,et al.  Kinematic Constraints on Glacier Contributions to 21st-Century Sea-Level Rise , 2008, Science.

[27]  Ian M. Howat,et al.  Rapid retreat and acceleration of Helheim Glacier, east Greenland , 2005 .

[28]  L. Stearns,et al.  Controls on the recent speed-up of Jakobshavn Isbræ, West Greenland , 2011, Journal of Glaciology.

[29]  Tavi Murray,et al.  Seasonal variation in velocity before retreat of Jakobshavn Isbræ, Greenland , 2005 .

[30]  David M. Holland,et al.  Acceleration of Jakobshavn Isbræ triggered by warm subsurface ocean waters , 2008 .

[31]  M. Pelto,et al.  Equilibrium State of Jakobshavns Isbræ, West Greenland , 1989, Annals of Glaciology.