上部海洋から大気への放射性炭素のオフセットは,急速な脱氷による二酸化炭素の放出を意味する
Kathryn A Rose1, Elisabeth L Sikes, Thomas P Guilderson
1Department of Geology, University of California, Davis, California 95616, USA.
Nature
|August 27, 2010
まとめ
海洋循環は,大気中の放射性炭素レベルに影響を与えます. この研究では,南大洋の上流が脱氷時に古い炭素を放出し,放射性炭素 (デルタ14C) 信号に影響を与え,北太平洋の炭素貯蔵庫への貢献を示唆していることが明らかになりました.
科学分野:
- パレオセアノグラフィー
- 気候科学 気候科学
- 放射性炭素年代測定法による年代測定
背景:
- 大気中の二酸化炭素 (CO2) と放射性炭素 (14C) のレベルは,海洋循環と炭素交換の影響を受けています.
- 最後の氷河期の間,大気中の低CO2は,大気中の高放射性炭素と相関しており,深海のCO2貯蔵と関連しています.
- 氷河期の終わりには,CO2が上昇し,大気中のデルタ14Cが減少し,深海からの古い炭素の放出を示唆しました.
研究 の 目的:
- 南西太平洋および南洋の表面および中間水域の放射性炭素記録を調査する.
- 氷河期から氷河期間の移行期における炭素放出の源と経路を理解する.
- 氷退期の炭素循環の変化における南洋の役割を再評価する.
主な方法:
- 南西太平洋と南洋の2つの堆積物核における放射性炭素 (デルタ14C) の分析.
- 海洋デルタ14C記録と大気放射性炭素データの比較.
- 放射性炭素信号と,上流と生物学的生産性の証拠の相関.
主要な成果:
- デルタ14Cの有意な減少は,大気の変化に先行し,それに合わせて,地表と中間水域で観察されました.
- 南大洋の上昇と海洋の生産性の強化は,大気中の放射性炭素の減少と一致しました.
- 南洋の上流によって放出された二酸化炭素は,大気の交換によって,その枯渇した14Cのサインを失いました.
結論:
- 氷河解凍による炭素の放出における南洋の役割は,以前の仮説とは異なる可能性がある.
- 観測されたデルタ14Cの枯渇は,北太平洋の炭素貯蔵庫からの貢献を示唆しています.
- 南太平洋を横断して北に移動する浅い水域は,CO2の脱ガスと生物学的吸収による最小限の枯渇-14C信号を示しました.
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