[M-IS05] Global climate change driven by the Southern Ocean and the Antarctic Ice Sheet

[MIS05-P14] Incorporation of grounding line parameterizations in the ice sheet model SICOPOLIS and its application to Antarctica

*Takashi Obase¹, Ayako Abe-Ouchi^1,2, Fuyuki SAITO³, Ralf Greve⁴, Kaho Harada¹ (1.Atmosphere and Ocean Research Institute, The University of Tokyo, 2.National Institute of Polar Research, Japan, 3.Japan Agency for Marine-Earth Science and Technology, 4.Institute of Low Temperature Science, Hokkaido University)

The flow of the Antarctic ice sheet in large-scale ice sheet modeling is often represented by the shallow ice approximation (SIA) , the shallow shelf approximation (SSA) or combinations of them. However, under a coarse horizontal resolution (O ~10 km), which is necessary for simulations of the paleoclimate and long-term future, a combined SIA/SSA model has limited performance in simulating the migration of grounding lines. In this study, a sub-grid grounding line parameterization is incorporated in the 3-dimensional ice sheet model SICOPOLIS to improve the representation of grounding line dynamics. We employed the grounding line parameterization by Schoof (2007), which computes the ice velocity based on the sub-grid horizontal ice flux across the grounding line.

First, we conduct the MISMIP2 experiments, which are hysteresis experiments under idealized bedrock topography and parameters to check the fundamental performance of grounding line migrations[GRG1] . The simulated grounding line positions exhibited hysteresis behavior to perturbations, which is largely in agreement with other ice sheet models.

Next, we conduct equilibrium experiments under a present-day climate condition with freely evolving ice sheet topography to examine the performance of the present-day simulation. The results indicate that the grounding line parameterization tends to increase the volume of the Antarctic ice sheet in total, but the simulated advances/retreats of the grounding line positions depend on the regions. We also conduct idealized atmospheric and oceanic warming experiments to examine the effect of grounding line parameterizations on the speed and extent of the retreat of the Antarctic ice sheet. The results suggest that the difference in the formulations in basal sliding could induce greater difference in the volume change of Antarctic ice sheet than the grounding line parameterization, but further analysis and careful treatments of the uncertain parameters are needed.