パレオゲン時代に大気中の二酸化炭素濃度が著しく低下した
Mark Pagani1, James C Zachos, Katherine H Freeman
1Department of Geology and Geophysics, Yale University, 210 Whitney Avenue, New Haven, CT 06511, USA.
まとめ
大気中の二酸化炭素 (CO2) 濃度は,エオセーン時代に高かったが,オリゴセーン時代に徐々に低下し,現代のレベルに達した. このCO2の減少は,南極の氷床の膨張とC4光合成の進化を容易にした.
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
- パレオセアノグラフィー
- イソトープ地球化学 イソトープ地球化学
背景:
- 大気中の二酸化炭素 (CO2) とパレオゲン期の気候の関係については,まだはっきりしていない.
- 過去のCO2レベルを理解することは,気候の動態を再構築するために非常に重要です.
研究 の 目的:
- エオセンの中期からオリゴセンの末期 (4500万~250万年前) の大気中のCO2レベルを再構築する.
- CO2の変化がパレオジンの気候と生態系に与える影響を調査する.
主な方法:
- 二不飽和アルケノンの安定した炭素同位体値の分析.
- 深海の堆積物からアルケノンを抽出する.
主要な成果:
- 大気中のCO2濃度は,エオセンの中期から後半にかけて1000〜1500ppmの範囲であった.
- CO2はオリゴセーン全体でいくつかの段階で減少し,オリゴセンの終わりまでに現代のレベルに達しました.
- 観測されたCO2の減少は,南極の氷床の膨張とC4光合成の出現と相関していた.
結論:
- パレオゲン時代の気候は,長期のCO2変動によって強く影響を受けた.
- エオセヌ・オリゴセヌの移行は,CO2の減少によって引き起こされた地球の気候システムにおける重要な変化を示した.
- 再構築されたCO2トレンドは,パレオジンの主要な環境変化を理解するための枠組みを提供します.
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