Abstract
It is well known that deterministic two-dimensional marine ice sheets can only be stable if the grounding line is positioned at a sufficiently steep, downward sloping bedrock. When bedrock conditions favour instabilities, multiple stable ice sheet profiles may occur. Here, we employ continuation techniques to examine the sensitivity of a two-dimensional marine ice sheet to stochastic noise representing short time scale variability, either in the accumulation rate or in the sea level height. We find that in unique regimes, the position of the grounding line is most sensitive to noise in the accumulation rate and can explain excursions observed in field measurements. In the multiple equilibrium regime, there is a strong asymmetry in transition probabilities between the different ice sheet states, with a strong preference to switch to the branch with a steeper bedrock slope.
Highlights
With the increasing global mean temperatures over the last decades, the behaviour of marine ice sheets, such as those on Greenland and Antarctica, has become a major topic in climate research
We have investigated the stochastic variability of marine ice sheets in a two-dimensional model with a specific bed topography (Schoof 2007a)
The deterministic model already has an interesting behaviour with unique regimes and a multiple equilibrium regime
Summary
With the increasing global mean temperatures over the last decades, the behaviour of marine ice sheets, such as those on Greenland and Antarctica, has become a major topic in climate research. We extend the analysis in Schoof (2007a) by forcing the marine ice sheet with noise resulting from small-scale variability in the accumulation rate or in sea level. The numerical approach allows us to efficiently analyse stable and unstable steady states, the corresponding grounding line fluxes and the response to noise, in particular stochastic induced transitions between equilibria. These phenomena can be investigated under a range of external conditions and different internal dynamics, including the gravitational effect of ice sheet variations on sea level variability (Gomez et al 2010). A summary and discussion of the results concludes the paper (§ 5)
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