南極西部の氷床、数百年で消失か NASA「後退は制止できない」

アメリカ航空宇宙局(NASA)は5月12日、過去40年に及ぶ観測の結果、南極西部の氷床が温暖化の影響で急速に溶け出し、遅くとも数百年で完全に消失する可能性が高いことを確かめたと発表した。

アメリカ航空宇宙局(NASA)は5月12日、過去40年に及ぶ観測の結果、南極西部の氷床が温暖化の影響で急速に溶け出し、遅くとも数百年で完全に消失する可能性が高いことを確かめたと発表した。氷床がすべて溶けた場合、海面上昇は少なくとも1.2メートル、最大で5メートル前後に達する可能性もあると指摘している。

NASAによると、南極西部のアムンゼン海域の氷床をレーダー衛星の観測技術などを用いて測定したところ、氷床とその直下にある岩盤の隙間に温かい海水が入り込み、氷の融解が急速に進んでいることを確認した。氷床の一つでは、20年で約30キロも内側に融解が進んでいた。地球温暖化が影響しているとみられ、これら氷河の後退は「元に戻ることが可能な範囲をすでに越えた。氷床の後退は制止不可能だ」と推測している。

Open Image Modal

The Amundsen Sea glacier beds are below sea level and slope deeper as they continue inland. This image shows the beds of Thwaites and Haynes glaciers, with colors indicating depth. The blue area under Thwaites Glacier is almost three-quarters of a mile below sea level.

一方、この研究とは別に、アメリカ・ワシントン大学の研究チームは12日、南極西部の同じ地域で、沿岸氷河の融解によって氷床が崩壊し始めているというコンピューターによるデータ解析結果をアメリカの科学誌「サイエンス」に発表した。早ければ200年~千年後に巨大氷床が崩壊して大規模な海面上昇が起きると予測している。

国連の気候変動に関する政府間パネル(IPCC)が2013年まとめた最新の報告書には、今回の研究成果は反映されていない。この報告書は、世界の平均海面が今世紀末に最大80センチ前後上昇すると見積もっていた

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