まとめ
化石の殻は,北大西洋の深海の栄養分レベルを20万年以上にわたって明らかにしています. 栄養素が乏しい水の供給は氷河期に減少したので,大陸の炭素の変動が少ないことを示唆している.
科学分野:
- パレオセアノグラフィー
- 海洋地化学は海洋地化学である.
- フォラミニフェラの研究
背景:
- ベンシックフォラミニフェラ殻のカドミウム/カルシウム比は,北大西洋深水 (NADW) の組成を反映しています.
- 海洋カドミウム分布は栄養分分布を反映し,Cd/Caは過去の栄養分レベルのプロキシになります.
- 栄養循環におけるNADWの役割を理解することは,気候の再構築に不可欠です.
研究 の 目的:
- 北大西洋の栄養分配の時間的な変動を過去20万年にわたって再構築する.
- NADWの栄養含有量に対する氷河期の影響を評価する.
- 大陸の炭素在庫の変動性を評価する.
主な方法:
- 北大西洋の堆積物核から採取したベンシックフォラミニフェラの化石殻におけるカドミウム/カルシウム比の分析.
- 過去20万年にわたる堆積物コアのデータを活用して.
- 炭素同位体データの統合.
主要な成果:
- 北大西洋の深海に栄養素が乏しい水源が継続的に供給されていることは,過去20万年にわたって確認されている.
- この栄養素が乏しい源の貢献は,重度の氷河期の間に約50%減少した.
- カドミウム/カルシウムのデータは,大陸の炭素在庫の変動が前述の仮説よりも少ないことを示している.
結論:
- ベンシックフォラミニフェラのCd/Ca比は,北大西洋の過去の栄養分変動の堅実な記録を提供します.
- 氷河期は,北大西洋の栄養素が枯渇した水質と栄養素が豊富な水質のバランスを大きく変えた.
- この研究は,氷河期と氷河期間のサイクルにおける大陸の炭素在庫の変動の大きさに関する以前の仮定に異議を唱える.
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