太平洋の氷河深層の換気
Wallace Broecker1, Stephen Barker, Elizabeth Clark
1Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W/Post Office Box 1000, Palisades, NY 10964, USA. broecker@ldeo.columbia.edu
まとめ
深海の核の放射性炭素年代測定は,氷河期の海洋の換気率は,今日と同じであったことを明らかにしています. これは,氷河期における大気中の炭素14濃度の上昇と,深海循環の減速を結びつける理論に異議を唱えている.
科学分野:
- パレオセアノグラフィー
- マリン・ジオケミストリー 海洋地化学
背景:
- 過去の海洋循環を理解することは,気候モデリングに不可欠です.
- 氷河期間の大気中の二酸化炭素の調節における深海の換気の役割は,依然として議論されている.
- 放射性炭素 (14C) は,海洋循環と炭素循環の重要なトレーサーである.
研究 の 目的:
- 放射性炭素年代測定を用いて,氷河のピーク期における深海の換気率を調査する.
- 氷河期における大気14C/C比に対する海洋循環の変化の寄与を評価する.
主な方法:
- 深海のコアから共存するベンティックとプランクティックフォラミニフェラの放射線年代測定.
- 同じ場所から並行して存在した木材とプランクトンのフォラミニフェラの放射線年代測定.
- 放射性炭素年代を比較して,水質年齢と表面/海洋/大気14C/Cの差を復元した.
主要な成果:
- 氷河期のピーク期における太平洋の深海 (深さ2km) の放射性炭素年代は,現在の年代より古くはなかった.
- 大気と表面の海洋間の14C/C比の差は,氷河期と現代時代に似ている.
- これらの発見は,氷河期の間,深海の換気が有意に減速しなかったことを示唆しています.
結論:
- 深海の循環と換気率は,氷河期と氷河間期の間に比較可能であった.
- 深海の換気の減速が,氷河期における大気中の14C/C比の増加の主な要因である可能性は低い.
- 過去の海洋学的な条件は,海洋および陸上の材料の放射性炭素年代測定を使用して効果的に再構築することができます.
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