大気中のCO2の減少によって引き起こされた南極の急速なケノゾイク氷河化
Robert M DeConto1, David Pollard
1Department of Geosciences, University of Massachusetts, Amherst, Massachusetts 01003, USA. deconto@geo.umass.edu
Nature
|January 17, 2003
まとめ
エオセーン/オリゴセーン境界における地球温暖化は,二酸化炭素 (CO2) 濃度の低下によるもので,海洋ゲートウェイの開口によるものではない. この二酸化炭素の限界値が南極の氷床の急速な成長を開始し,地球気候を根本的に再構築しました.
科学分野:
- 古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは,古代気候学 (paleoclimatology) とは
- 気候モデリング
- 地質学の歴史 地質学の歴史
背景:
- エオセーン/オリゴセーン境界 (約. 3400万年前) は,地球温暖化と南極の氷河形成を象徴した.
- 以前の理論では,この氷河期は南洋の入り口と南極環極流の開きによるものと考えられていた.
- この大きな気候変動の再編成の正確なメカニズムと主要な原動力については,議論が続いている.
研究 の 目的:
- 東南極氷床の形成と早期の成長をシミュレートする.
- 南極氷河期におけるCO2濃度と南洋のゲートウェイ開口の相対的な役割を調査する.
- この臨界期における世界的な気候変動の根本的な原動力を理解する.
主な方法:
- 大気,海洋,氷床,堆積物成分を組み合わせた包括的な一般循環モデルを使用した.
- パレオジオグラフィー,温室効果ガス濃度 (CO2),軌道パラメータ,海洋熱伝搬をモデルに組み込みました.
- 様々な環境条件下で氷河の形成と膨張のプロセスをシミュレートしました.
主要な成果:
- 南極氷河の主要な引き金として,ケノゾイク期のCO2濃度の低下が特定されました.
- モデルシミュレーションでは,南極高原の小さな氷冠の初期形成が続いて急速な膨張が示されました.
- 特定のCO2値が特定され,その値を超えると,ポジティブなフィードバックにより氷床の成長が加速した.
- 南洋のゲートウェイの開通は,二酸化炭素濃度と比較して二次的な役割を果たしていることが判明しました.
結論:
- このシミュレーションは,エオセーン/オリゴセーン境界における南極氷河化の主要な原動力として,二酸化炭素の減少を裏付けている.
- 氷床の高さ/質量バランスのフィードバックと軌道の変化は,CO2の値を超えると,氷河化を増幅しました.
- この研究は,主要な古気候の移行における地質学と大気学的要因の重要性を再評価しています.
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