Journal cover Journal topic
The Cryosphere An interactive open-access journal of the European Geosciences Union
doi:10.5194/tc-2017-37
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
20 Mar 2017
Review status
This discussion paper is under review for the journal The Cryosphere (TC).
Ice-shelf damming in the glacial Arctic Ocean: dynamical regimes of a basin-covering kilometre thick ice shelf
Johan Nilsson1,2, Martin Jakobsson3,2, Chris Borstad4, Nina Kirchner5,2, Göran Björk6, Raymond T. Pierrehumbert7, and Christian Stranne3,2 1Department of Meteorology, Stockholm University
2Bolin Centre for Climate Research, Stockholm University
3Department of Geological Sciences, Stockholm University
4The University Centre in Svalbard
5Department of Physical Geography, Stockholm University
6Department of Marine Sciences, University of Gothenburg
7Department of Physics, University of Oxford
Abstract. Recent geological and geophysical data suggest that a one-kilometre thick ice shelf extended over the glacial Arctic Ocean during Marine Isotope Stage 6, about 140 000 years ago. Here, we theoretically analyse the development and equilibrium features of such an ice shelf, using scaling analyses and a one-dimensional ice-sheet–ice-shelf model. We find that the dynamically most consistent scenario is an ice shelf with a nearly uniform thickness that covers the entire Arctic Ocean. Further, the ice shelf have two regions with distinctly different dynamics: a vast interior region covering the central Arctic Ocean and an exit region towards the Fram Strait. In the interior region, which is effectively dammed by the Fram Strait constriction, there are strong back stresses and the mean ice-shelf thickness is controlled primarily by the horizontally-integrated mass balance. A narrow transitions zone is found near the continental grounding line, in which the ice-shelf thickness decreases offshore and approaches the mean basin thickness. If the surface accumulation and mass flow from the continental ice masses are sufficiently large, the ice-shelf thickness grows to the point where the ice shelf grounds on the Lomonosov Ridge. As this occurs, the back stress increases in the Amerasian Basin and the ice-shelf thickness becomes larger there than in the Eurasian Basin towards the Fram Strait. Using a one-dimensional ice-dynamic model, the stability of equilibrium ice-shelf configurations without and with grounding on the Lomonosov Ridge are examined. We find that the grounded ice-shelf configuration should be stable if the two Lomonosov Ridge grounding lines are located on the opposites sides of the ridge crest, implying that the downstream grounding line is located on a downward sloping bed. This result shares similarities with the classical result on marine ice-sheet stability of Weertman, but due to interactions between the Amerasian and Eurasian ice-shelf segments the mass flux at the downstream grounding line decreases rather than increases with ice thickness.

Citation: Nilsson, J., Jakobsson, M., Borstad, C., Kirchner, N., Björk, G., Pierrehumbert, R. T., and Stranne, C.: Ice-shelf damming in the glacial Arctic Ocean: dynamical regimes of a basin-covering kilometre thick ice shelf, The Cryosphere Discuss., doi:10.5194/tc-2017-37, in review, 2017.
Johan Nilsson et al.
Johan Nilsson et al.
Johan Nilsson et al.

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Short summary
Recent data suggest that a one-kilometre thick ice shelf extended over the glacial Arctic Ocean during MIS 6, about 140 000 years ago. Here, we theoretically analyse the development and equilibrium features of such an ice shelf. The ice shelf was effectively dammed by the Fram Strait and the mean ice-shelf thickness was controlled primarily by the horizontally-integrated mass balance. Our results can aid to resolve some outstanding questions of the state of the glacial Arctic Ocean.
Recent data suggest that a one-kilometre thick ice shelf extended over the glacial Arctic Ocean...
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