Seismic evidence for complex sedimentary control of Greenland Ice Sheet flow
Permanent link
https://hdl.handle.net/10037/12459Date
2017-08-16Type
Journal articleTidsskriftartikkel
Peer reviewed
Author
Kulessa, Bernd; Hubbard, Alun Lloyd; Booth, Adam D.; Bougamont, Marion; Dow, Christine F.; Doyle, Samuel H.; Christoffersen, Poul; Lindbäck, Katrin; Pettersson, Rickard; Fitzpatrick, Andrew A.W.; Jones, Glenn A.Abstract
The land-terminating margin of the Greenland Ice Sheet has slowed down in recent decades, although the causes
and implications for future ice flow are unclear. Explained originally by a self-regulating mechanism where basal slip
reduces as drainage evolves from low to high efficiency, recent numerical modeling invokes a sedimentary control
of ice sheet flow as an alternative hypothesis. Although both hypotheses can explain the recent slowdown, their
respective forecasts of a long-term deceleration versus an acceleration of ice flow are contradictory. We present
amplitude-versus-angle seismic data as the first observational test of the alternative hypothesis. We document transient
modifications of basal sediment strengths by rapid subglacial drainages of supraglacial lakes, the primary current
control on summer ice sheet flow according to our numerical model. Our observations agree with simulations of
initial postdrainage sediment weakening and ice flow accelerations, and subsequent sediment restrengthening and
ice flow decelerations, and thus confirm the alternative hypothesis. Although simulated melt season acceleration of
ice flow due to weakening of subglacial sediments does not currently outweigh winter slowdown forced by selfregulation,
they could dominate over the longer term. Subglacial sediments beneath the Greenland Ice Sheet must
therefore be mapped and characterized, and a sedimentary control of ice flow must be evaluated against competing
self-regulation mechanisms.
Description
Source at: http://doi.org/10.1126/sciadv.1603071