Journal cover Journal topic
The Cryosphere An interactive open-access journal of the European Geosciences Union
doi:10.5194/tc-2016-235
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
31 Oct 2016
Review status
This discussion paper is under review for the journal The Cryosphere (TC).
From Heinrich Events to cyclic ice streaming: the grow-and-surge instability in the Parallel Ice Sheet Model
Johannes Feldmann1 and Anders Levermann1,2,3 1Potsdam Institute for Climate Impact Research (PIK), Potsdam, Germany
2Institute of Physics, University of Potsdam, Potsdam, Germany
3LDEO, Columbia University, New York, USA
Abstract. Here we report on a cyclic, physical ice-discharge instability in the Parallel Ice Sheet Model, simulating the flow of a three-dimensional, inherently buttressed ice-sheet-shelf system which periodically surges on a millennial timescale. The thermo-mechanically coupled model on 1 km horizontal resolution includes an enthalpy-based formulation of the thermodynamics, a non-linear stress-balanced based sliding law and a very simple sub-glacial hydrology. The simulated unforced surging is characterized by rapid ice streaming through a bed trough, resulting in abrupt discharge of ice across the grounding line which is eventually calved into the ocean. We identify and visualize the central feedbacks that dominate the sub-sequent phases of ice build-up, surge and stabilization which emerge from the interaction between ice dynamics, thermodynamics and the sub-glacial till layer. A reduction in the surface mass balance or basal roughness yields a damping of the feedback loop which suggests that thinner ice sheets may be less susceptible to surging. The presented mechanisms underlying our simulations of self-maintained, periodic ice growth and destabilization may play a role in large-scale ice-sheet surging, such as the surging of the Laurentide Ice Sheet, which is associated with Heinrich Events, and ice-stream shut-down and reactivation, such as observed in the Siple Coast region of West Antarctica.

Citation: Feldmann, J. and Levermann, A.: From Heinrich Events to cyclic ice streaming: the grow-and-surge instability in the Parallel Ice Sheet Model, The Cryosphere Discuss., doi:10.5194/tc-2016-235, in review, 2016.
Johannes Feldmann and Anders Levermann
Johannes Feldmann and Anders Levermann
Johannes Feldmann and Anders Levermann

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