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東アフリカ赤道付近のモンスーン降雨の半プレセッショナルな動態
Dirk Verschuren1, Jaap S Sinninghe Damsté, Jasper Moernaut
1Limnology Unit, Department of Biology, Ghent University, Ledeganckstraat 35, 9000 Gent, Belgium. dirk.verschuren@UGent.be
Nature
|December 4, 2009
まとめ
赤道東アフリカからの過去の気候記録は,モンスーンの降雨が軌道内太陽化力によって変化していたことを明らかにしています. この研究は,2万5千年にわたる水文学的変化を記録し,太陽のサイクルと地域的な気候の動態に対する明確な反応を示しています.
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
- 気候のダイナミクス
- 地質化学 地質化学
背景:
- 地域的な気候の変動を理解するには,過去の気候の詳細な記録,特にデータ不足の赤道地域からの詳細な記録が必要です.
- ビモダルの降雨量を持つ赤道地域は,気候強制を理解するために不可欠ですが,高品質のプロキシ記録はほとんどありません.
研究 の 目的:
- 過去2万5千年の間,東アフリカ赤道地域における過去の水文学的変動を再構築する.
- この地域における軌道内太陽化強制とモンスーンの降雨パターンとの関係を調査する.
- 赤道気候に起因する高緯度低緯度気候の影響を区別する.
主な方法:
- チャラ湖の堆積物からの連続した,高解像度の気候プロキシ記録の分析.
- 地震反射ストラティグラフィーを用いて堆積層を解釈する.
- 過去の水文状態を再構築するために有機バイオマーカー分子を使用します.
主要な成果:
- 赤道東アフリカにおける水文学的変動は,軌道内太陽化強制と同期した~11,500年 (半プレセッショナル) の間隔で発生した.
- 東南と北東のモンスーンの交代的な強化は,最大半球間太陽照射グラデーションと相関しています.
- 乾燥した条件は,弱まったモンスーンと,特定の季節のローカル・インソレーションの減少と一致しました.
結論:
- 赤道東アフリカのモンスーンの降雨は,主に低緯度の太陽照射が軌道時間スケールに強制することによって引き起こされます.
- サブミレニアムの水文学的変化は,高北緯度の影響を示しますが,軌道スケールの変化は,低緯度の強制によって支配されています.
- この地域の気候の動態は,その大陸の位置と大西洋の気候調節システムとの限られた接続の影響を受けています.
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