南極海の深層の換気と脱氷によるCO2の上昇
L C Skinner1, S Fallon, C Waelbroeck
1Godwin Laboratory for Palaeoclimate Research, Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK. lcs32@esc.cam.ac.uk
Science (New York, N.Y.)
|May 29, 2010
まとめ
氷河期には,深海の二酸化炭素 (CO2) が放出され,大気中のCO2が上昇した. 南洋からの放射性炭素データは,氷河期間の古い深海を示し,これを確認しています. これは南大洋を支えている.
科学分野:
- パレオセアノグラフィー
- 気候科学 気候科学
- 海洋学 海洋学 海洋学
背景:
- 大気中の二酸化炭素 (CO2) 濃度は,過去の氷河期と氷河期間の周期で著しく変動した.
- これらのCO2の変化は,特に南大洋からの深海炭素の放出によって引き起こされるという仮説があります.
研究 の 目的:
- 過去の気候変動の際に大気中のCO2を調節する南洋の役割を調査する.
- 南洋経由の深海CO2放出が,氷河期と氷河期間の大気中のCO2濃度に影響を与えたという仮説を検証する.
主な方法:
- 南大洋の大西洋地域における放射性炭素 (14C) 濃度の分析.
- 氷河期と氷河期間の深海の放射性炭素年代を比較する.
- 大気中のCO2に深い水の循環が及ぼす影響をモデル化.
主要な成果:
- 南極圏の深水は,大気相対の現在のレベルと比較して,最後の氷河期の間に2倍以上の年齢であることが判明しました.
- この"古い"深い水は,おそらく二酸化炭素に富んでいた.
- このCO2濃縮水が脱氷時に放出されることは,大気中のCO2の段階的な増加に寄与した.
結論:
- この発見は,南大洋が過去の脱氷期に封じ込められた二酸化炭素の急速な放出において重要な役割を果たしたという仮説を強く支持している.
- 南極の転覆循環によって調節される南極海の深い水の年齢とCO2含有量は,氷河期と氷河期間の大気CO2動態の重要な要因です.
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