北半球は,最後の脱氷期中に南半球の気候を強制した
Feng He1, Jeremy D Shakun, Peter U Clark
1Center for Climatic Research, Nelson Institute for Environmental Studies, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA. fenghe@wisc.edu
Nature
|February 8, 2013
まとめ
氷河周期に関するミランコビッチの理論は支持されているが,南半球の気候変動がそれを挑戦している. 私たちのモデルは,軌道強制が北半球の脱氷を引き起こし,大西洋南半球の逆転循環の変化が南半球の温暖化を説明していることを示しています.
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,古代気候学 (paleoclimatology) とは
- 気候モデリング
- 地球システム科学 地球システム科学
背景:
- ミランコビッチ理論は,北半球の夏の太陽照射が,氷床の質量バランスを通して氷河のサイクルを駆動すると仮定しています.
- 気候記録は,南半球の気候変化が北半球の変化と相乗っているか,あるいはその変化をリードしていることを示しており,この理論に異議を唱えている.
- 軌道強制への半球反応と独立した強制を区別するのは,信号処理だけで難しい.
研究 の 目的:
- 軌道の変化,CO2,氷床,大西洋南極反転循環 (AMOC) が半球温度に与える影響を調査する.
- 最後の脱氷期 (紀元前2万4千〜3千年) の脱氷の主な要因を特定する.
- 脱氷期間の半球気候変化のタイミングとリード/レイグを調和させるため.
主な方法:
- 結合された大気と海洋の一般循環モデルを用いた一時的なシミュレーション.
- シミュレーションには,軌道パラメータ,大気中のCO2,氷床,AMOCからのフォークリングが含まれていました.
- 分析は,半球表面温度の進化と,脱氷のプロキシ記録との比較に焦点を当てた.
主要な成果:
- 軌道変化だけを使ったシミュレーションは,北半球の太陽照射と雪アルベドフィードバックによって開始された脱氷を示し,ミランコビッチ理論を支持した.
- すべての強制を組み込んだシミュレーションは,タイミングと大きさを含め,南半球の表面温度の進化を最も良く再現しました.
- 軌道によって引き起こされる北半球の氷床の退却によって引き起こされるAMOCの変化は,南半球の早期温暖化の最も妥当な原因です.
結論:
- 軌道強制は北半球の脱氷を引き起こした.
- 大西洋南極反転循環 (AMOC) の変化は,南半球の早期温暖化と北半球よりも優位性を説明する可能性がある.
- 大気中の二酸化炭素濃度の上昇は,地球規模の氷河解凍に重大な肯定的なフィードバックをもたらした.
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