Collapse of Antarctic ice sheet and sea level rise in the Last Interglacial

近年，極域氷床の融解が急速なペースで進行中であることが明らかになり，温暖化によって海水準が大きく上昇する懸念が高まっている．産業革命前よりも僅かに温暖な最終間氷期（13万～11.5万年前）には，6～9mもの急激な海水準上昇があったとされる．これが事実なら，現在と似た気候状態で，南極氷床の大規模な崩壊を誘発する臨界点が存在することになる．現在の平均的な気候状態はすでに最終間氷期のレベルに達しており，南極氷床の大規模な崩壊が将来に起こり得る可能性の検証は喫緊の課題と言える．本稿では最終間氷期の気候状態や海水準変動，南極氷床の安定性についての最新の知見を解説し，将来，南極氷床の大規模融解が引き起こされる可能性について考察する．Recent observations have revealed that the fastest melting rate of polar ice sheets ever observed is ongoing and there is growing concern of significant rise of sea level in the future. Geological records have suggested that abrupt rises in sea level (6-9 m rise) happened during the Last Interglacial when global mean sea surface temperature was slightly higher than the preindustrial level. If this were really happening, there is a critical ice sheet stability threshold resulting in the catastrophic collapse of polar ice sheets and substantial rapid sea-level rise in the interglacial climate regime. Given that the current global mean SST has already reached the Last Interglacial level, it is urgent issue to evaluate whether massive collapse of the Antarctic ice sheets could occur in the future. In this article, we review climate state, sea level fluctuation and stability of Antarctic ice sheet in the Last Interglacial