Abstract
Abstract. In this paper, we present the GRISLI (Grenoble ice sheet and land ice) model in its newest revision (version 2.0). Whilst GRISLI is applicable to any given ice sheet, we focus here on the Antarctic ice sheet because it highlights the importance of grounding line dynamics. Important improvements have been implemented in the model since its original version (Ritz et al., 2001). Notably, GRISLI now includes a basal hydrology model and an explicit flux computation at the grounding line based on the analytical formulations of Schoof (2007) or Tsai et al. (2015). We perform a full calibration of the model based on an ensemble of 300 simulations sampling mechanical parameter space using a Latin hypercube method. Performance of individual members is assessed relative to the deviation from present-day observed Antarctic ice thickness. To assess the ability of the model to simulate grounding line migration, we also present glacial–interglacial ice sheet changes throughout the last 400 kyr using the best ensemble members taking advantage of the capacity of the model to perform multi-millennial long-term integrations. To achieve this goal, we construct a simple climatic perturbation of present-day climate forcing fields based on two climate proxies: atmospheric and oceanic. The model is able to reproduce expected grounding line advances during glacial periods and subsequent retreats during terminations with reasonable glacial–interglacial ice volume changes.
Highlights
Continental ice sheets are a major climatic component for Earth system dynamics
We provide details on some components which are currently not documented in international scientific journals
Since the global volume is an integrated metric that does not account for potential systematic compensation, in Fig. 5 we show the root mean square error (RMSE) in ice thickness for each ensemble member with respect to observations (Fretwell et al, 2013)
Summary
Continental ice sheets are a major climatic component for Earth system dynamics. They operate on a variety of timescales, from diurnal to multi-millennial, through multiple feedbacks such as temperature – surface albedo, gravity waves and oceanic circulation changes related to freshwater flux release. While the two current ice sheets have been mostly stable for at least the last 1000 years, they are expected to contribute to future sea level rise, albeit with a largely uncertain magnitude. Abe-Ouchi et al, 2013; Gregoire et al, 2012) Another source of instability, for marine ice sheets such as the palaeo Barents–Kara or present-day Antarctic ice sheets, is related to the fact that large parts of the bedrock present a retrograde slope from the grounding line.
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