Timothy Birdnow

TImothy Birdnow

Acceleration of Jakobshavn Isbræ triggered by warm subsurface ocean waters
David M. Holland, Robert H. Thomas, Brad de Young, Mads H. Ribergaard &
Bjarne Lyberth

Observations over the past decades show a rapid acceleration of several outlet glaciers in Greenland and Antarctica. One of the largest changes
is a sudden switch of Jakobshavn Isbræ, a large outlet glacier feeding
a deep-ocean fjord on Greenland’s west coast, from slow thickening to
rapid thinning in 1997, associated with a doubling in glacier velocity.
Suggested explanations for the speed-up of Jakobshavn Isbræ include
increased lubrication of the ice bedrock interface as more meltwater
has drained to the glacier bed during recent warmer summers and
weakening and break-up of the floating ice tongue that buttressed the
glacier. Here we present hydrographic data that show a sudden increase
in subsurface ocean temperature in 1997 along the entire west coast of
Greenland, suggesting that the changes in Jakobshavn Isbræ were instead
triggered by the arrival of relatively warm water originating from the
Irminger Sea near Iceland. We trace these oceanic changes back to changes in the atmospheric circulation in the North Atlantic region. We conclude that the prediction of future rapid dynamic responses of other outlet glaciers to climate change will require an improved understanding of the effect of changes in regional ocean and atmosphere circulation on the delivery of warm subsurface waters to the periphery of the ice sheets.

Yours sincerely
Jens Kieffer-Olsen, M.Sc.(Elec.Eng.)
Slagelse, Denmark

From CCNET