[M-IS08] 南大洋・南極氷床が駆動する全球気候変動

[MIS08-P04] A multi-phase spin-up method for the Antarctic ice sheet

Tom Dangleterre^1,2、*Ralf Greve^1,3、Constantijn J Berends⁴、Jorge Bernales⁴ (1.Institute of Low Temperature Science, Hokkaido University、2.Graduate School of Environmental Science, Hokkaido University、3.Arctic Research Center, Hokkaido University、4.Institute for Marine and Atmospheric Research Utrecht, Utrecht University)

キーワード：Antarctica, Ice sheet, Antarctic ice sheet, Initialization, Spin-up, Modelling

Ice sheets play a critical role in the Earth's climate system, and their evolution is closely linked to the global temperature and sea level. Numerical modelling has become an important tool for estimating the contribution of the Earth's ice sheets to sea-level rise over the coming centuries. Such simulations depend on reasonably accurate initial conditions of the recent 3D dynamic/thermodynamic state of the ice sheet in question. Since observational data are limited, numerical tools are required to obtain these initial conditions, which can be classified into assimilation methods and spin-up methods. Here, we propose a multi-phase spin-up method for the Antarctic ice sheet, simulated with the model SICOPOLIS. It consists of the following steps: (1) a 100-ka steady-state calibration phase that includes preliminary tuning of the basal sliding coefficient, (2) a freely evolving glacial phase from the Eemian interglacial until the Last Glacial Maximum (LGM), (3) a deglaciation phase from the LGM until the early Holocene that includes fine-tuning of basal sliding and topography-nudging to produce an ice-sheet configuration close to present day, (4) a freely evolving Holocene phase from the early Holocene until today. This will produce a present-day ice sheet that includes the thermal, sea-level, and glacial-isostatic-adjustment signals. We will use the initialized ice sheet to carry out selected future-climate test simulations.