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大西洋南極循環の崩壊と急速な再開は,脱氷期気候変化と関連しています
J F McManus1, R Francois, J-M Gherardi
1Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA. jmcmanus@whoi.edu
Nature
|April 23, 2004
まとめ
大西洋南極の転覆循環は,最後の脱氷期,特にハインリッヒ事件H1.1の周辺で,ほとんど停止しました. その後の再加速は,主要な地域温暖化イベントと一致し,急激な気候変動におけるその役割を確認しました.
科学分野:
- パレオセアノグラフィー
- 気候科学 気候科学
- 地質化学 地質化学
背景:
- 大西洋南極逆転循環 (AMOC) は,地球温暖化に大きく影響している.
- 以前の研究では,堆積物の栄養代理物からAMOCの変化を推論したが,循環速度の制約はなかった.
- AMOCの変動による気候への影響を評価することは,過去の再構築方法の限界のために困難でした.
研究 の 目的:
- 大西洋南極の転覆循環の速度における過去の変化を定量化するために.
- 最後の脱氷期におけるAMOCダイナミクスと突然の気候変化の関係を調査する.
- 地域および世界の気候に対するAMOCの影響のより正確な評価を提供するために.
主な方法:
- AMOCのシナマティックプロキシとして231Pa/230Th比を使用した.
- 亜熱帯北大西洋の堆積物核を分析した.
- 堆積物層における放射性核素濃度測定により,過去のAMOC強度を再構築した.
主要な成果:
- AMOCは,ハインリッヒイベントH1 (17,500年前) の間,ほぼまたは完全に消滅し,若年ドライアスの寒冷イベント (12,700年前) の間,減少した.
- 急速なAMOC再加速は,脱氷期間の2つの最も重要な地域温暖化イベントと同時に観察されました.
- 231Pa/230Thの記録は,AMOCの変動性と急激な気候変動の間の強い相関を示しています.
結論:
- 大西洋南極の転覆循環の速度の変化は,急激な気候変動の重要な要因である.
- この研究は,AMOCダイナミクスが過去の気候移行を調節する上で重要な役割を果たしていることを確認しています.
- 231Pa/230Thプロキシは,過去転覆の循環速度の強固な制約を提供し,気候再構築を改善します.
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