南極環極流における転覆循環の短路化
Alberto C Naveira Garabato1, David P Stevens, Andrew J Watson
1School of Ocean and Earth Science, National Oceanography Centre, Southampton SO14 3ZH, UK. acng@noc.soton.ac.uk
Nature
|May 15, 2007
まとめ
南洋の上流と混合は,以前にモデル化されたものより速い. 天然ヘリウムトレーサー実験は,急速な深水帰還経路を明らかにし,地球規模の海洋循環のショート回路を示唆しています.
科学分野:
- 海洋学 海洋学 海洋学
- 気候科学 気候科学
- 地質化学 地質化学
背景:
- 海洋の転覆循環は,地球規模の気候の調節と栄養素の循環に不可欠です.
- 南極環極流 (ACC) の混合は,深水の表面への帰還を制御することによって,この循環に重大な影響を及ぼします.
- 南洋の混合と上流の速度の現在の推定は,観測データによってほとんど制約されていません.
研究 の 目的:
- 南極環極流の中間層における混合と上流の速度を定量化するために.
- 熱水噴出孔から自然に放出されるトレーサーを,ユニークな実験ツールとして利用する.
主な方法:
- ドレイク・パサージの近くの熱水噴出口から注入されたマントルヘリウムを用いた自然トレーサー実験.
- ACCの中間層のヘリウム分散を,重要な環極セクター全体で追跡する.
- トレーサーの分散速度を測定し,混合と上流を推測する.
主要な成果:
- 密度面に沿って観測された上流の速度は速い.
- 密度面の間で激しい混合率が検出されました.
- アップウェリングとミキシングの速度は,典型的な南洋の逆転循環モデルで使用される速さよりも約1桁高い.
結論:
- 発見は,ACCの粗な海底地形の上に深い水の経路が強化され,複雑であることを示唆しています.
- これらのプロセスは,これらの地域内の世界的な転覆循環に"ショート回路"を生じさせる可能性があります.
- これは,海洋循環と熱/炭素輸送の規制における局所的な混合と上流の重要な役割を強調しています.
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