[M-IS05] 南大洋・南極氷床が駆動する全球気候変動

[MIS05-05] Long-term future projections for the Antarctic ice sheet with the model SICOPOLIS

*Christopher Chambers¹、Ralf Greve^2,1、Takashi Obase³、Fuyuki SAITO⁴、Kaho Harada³、Ayako Abe-Ouchi³ (1.Institute of Low Temperature Science, Hokkaido University、2.Arctic Research Center, Hokkaido University、3.Atmosphere and Ocean Research Institute, University of Tokyo、4.Japan Agency for Marine-Earth Science and Technology)

キーワード：Antarctica, ice sheet, climate change, cryosphere

Ice-sheet simulations of extended versions of ISMIP6 (Ice Sheet Model Intercomparison Project for the Coupled Model Intercomparison Project Phase 6) future climate experiments for the Antarctic ice sheet until the year 3000 are used to investigate the long term impacts of 21st century projected warming. The simulations use climate projections from the beginning of 2015 until the end of 2100, after which no further climate trend is applied. Fourteen experiments are for the “unabated warming” pathway, and three are for the “reduced emissions” pathway. For the unabated warming path simulations, a large difference in the vulnerability of east and west Antarctica develops over hundreds of years (Figure 1 bottom), with west Antarctica suffering a much more severe ice loss than east Antarctica. In these cases, the mass loss amounts to a 14-experiment average of ~3.3 m sea-level equivalent by the year 3000 and ~5.3 m for the most sensitive experiment (Figure 1 top). For the reduced emissions pathway, the mean mass loss is ~0.25 m sea-level equivalent. The conclusions are quite different to ISMIP6, which saw only modest losses, or even gains, by the year 2100, demonstrating that the consequences of the unabated warming path are large and long term. Under the unabated 21st century warming scenario the ice sheet progresses through 4 phases, that are defined by differing rates of ice loss. The stages are attributable to how west Antarctica loses mass along the Siple Coast followed later by additional loss from the Thwaites/Pine Island region and an eventual leveling out in the rate of ice sheet loss once the majority of the west Antarctic ice sheet has melted. Simulations with and without bedrock rebound corroborate a negative feedback for ice loss found in previous studies. Limitations to the study, include the lack of accounting for local climatic changes in regions where ice sheet collapse occurs.