Abstract
Abstract. We present the effects of changing two sliding parameters, a deformational velocity parameter and two bedrock deflection parameters on the evolution of the Antarctic ice sheet over the period from the last interglacial until the present. These sensitivity experiments have been conducted by running the dynamic ice model ANICE forward in time. The temporal climatological forcing is established by interpolating between two temporal climate states created with a regional climate model. The interpolation is done in such a way that both temperature and surface mass balance follow the European Project for Ice Coring in Antarctica (EPICA) Dome C ice-core proxy record for temperature. We have determined an optimal set of parameter values, for which a realistic grounding-line retreat history and present-day ice sheet can be simulated; the simulation with this set of parameter values is defined as the reference simulation. An increase of sliding with respect to this reference simulation leads to a decrease of the Antarctic ice volume due to enhanced ice velocities on mainly the West Antarctic ice sheet. The effect of changing the deformational velocity parameter mainly yields a change in east Antarctic ice volume. Furthermore, we have found a minimum in the Antarctic ice volume during the mid-Holocene, in accordance with observations. This is a robust feature in our model results, where the strength and the timing of this minimum are both dependent on the investigated parameters. More sliding and a slower responding bedrock lead to a stronger minimum which emerges at an earlier time. From the model results, we conclude that the Antarctic ice sheet has contributed 10.7 ± 1.3 m of eustatic sea level to the global ocean from the last glacial maximum (about 16 ka for the Antarctic ice sheet) until the present.
Highlights
The variability of the Antarctic ice sheet (AIS) has a large impact on sea level and ocean circulation
In most evolutionary studies of the AIS over glacial timescales, the climatological forcing is produced by shifting temperatures linearly following proxy records from ice cores such as those from Vostok or the European Project for Ice Coring in Antarctica (EPICA) Dome C (e.g. Ritz et al, 2001; Huybrechts, 2002; Philippon et al, 2006), often corrected by applying a lapse rate to account for differences in the surface elevation
The effect of changing ESIA is strongest on the East Antarctic ice sheet (EAIS), where the movement of ice is mainly driven by deformation (Fig. 4)
Summary
The variability of the Antarctic ice sheet (AIS) has a large impact on sea level and ocean circulation. Its state depends strongly on geometric and climatic parameters. Many model studies have examined how the state and evolution of the AIS depend on those parameters Ritz et al, 2001; Huybrechts, 2002; Philippon et al, 2006), often corrected by applying a lapse rate to account for differences in the surface elevation. In these cases, a constant lapse rate is assumed for the entire ice sheet and no spatial correction is made to account for the differences between, for example, grounded ice and ice shelves.
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