南極の一時的な氷量回復は長期的傾向ではなく気候変動によるものと判明(Antarctica’s brief rebound was caused by climate variability, not a ‘new normal’)

2026-08-19 カリフォルニア大学サンタバーバラ校(UCSB)

南極では2021~2023年に降雪が大幅に増え、一時的に氷床の質量減少が鈍化したように見えたが、カリフォルニア大学サンタバーバラ校(UCSB)とワシントン大学などの研究チームは、これが長期的な「新常態」ではなく、自然な気候変動による一時的現象であることを示した。水蒸気の起源を追跡する計算解析から、東南極の異常な降雪は西太平洋・東インド洋の「熱帯ウォームプール」が2021~2023年に特に高温となり、大量の水蒸気を南極へ運んだことが原因と判明。過去にも同地域は数十年ごとに数年間温暖化した後、平年状態へ戻るパターンを示している。したがって今回の降雪増加が温暖化による南極の長期的な氷減少傾向を反転させたとは考えにくく、短期的変動と長期トレンドを区別する重要性が示された。

南極の一時的な氷量回復は長期的傾向ではなく気候変動によるものと判明(Antarctica’s brief rebound was caused by climate variability, not a ‘new normal’)
Photo Credit: Yoshihiro Nakayama
The Totten Ice Shelf contributes to ice loss in East Antarctica, but this was offset by the increased snowfall from 2021 to 2023.

<関連情報>

数年にわたる熱帯温暖水域の温暖化が南極の質量減少の減速を引き起こす Multiyear tropical warm pool warming drives slowdown in Antarctic mass loss

Yunhe Wang,Qinghua Ding,Xiaofeng Li,Thomas J. Ballinger,Yoshihiro Nakayama,Dániel Topál & Eric J. Steig
Nature  Published:19 August 2026
DOI:https://doi.org/10.1038/s41586-026-10912-x

Abstract

Antarctic mass loss has been a major contributor to global sea-level rise for most of the last few decades, mainly driven by West Antarctica1. During 2021–2023, however, a sharp increase in surface mass balance over Queen Mary Land and Wilkes Land in East Antarctica offset West Antarctic loss and slowed the rate of total ice mass loss2,3. Although this slowdown is consistent with the expected long-term precipitation response to global warming through poleward-shifted storm tracks and Antarctic moistening4, our results point to a different mechanism. Here we show that the recent ice mass gain was linked to a recurrent atmospheric teleconnection driven by sea surface temperature anomalies in the tropical warm pool, which experienced unusually persistent warming from 2021 to 2023 relative to the previous two decades. On the basis of observations and model experiments, we find that tropical warm pool warming excites a poleward-propagating Rossby-wave train that induces a high-pressure anomaly over East Antarctica, enhancing Queen Mary Land and Wilkes Land precipitation and driving the observed mass gain, with moisture primarily sourced from the mid-latitude Indian Ocean. Similar multiyear warming in the tropical warm pool recurs about once per decade in observations and historical simulations, and its influence on precipitation is distinct from the effects of global warming. Therefore, the recent Antarctic Ice Sheet mass gain is probably temporary and does not yet reflect a sustained, global-warming-driven moistening of Antarctica.

1702地球物理及び地球化学
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