窒素サイクリング. サブボックス海洋における素早い酸化窒素の循環
Andrew R Babbin1, Daniele Bianchi2, Amal Jayakumar3
1Department of Geosciences, Princeton University, Princeton, NJ 08544, USA. Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. babbin@mit.edu.
まとめ
海洋の窒素酸化物 (N2O) の循環は,以前考えられていたよりも速く,特にサブボキシクゾーンで起こっています. オーガニック炭素と酸素レベルによって引き起こされるこの急速な循環は,海洋からの温室効果ガス排出量の増加を示唆しています.
科学分野:
- 海洋学 海洋学とは
- 大気化学 大気化学
- バイオジオケミストリー バイオジオケミストリー
背景:
- 酸化窒素 (N2O) は強力な温室効果ガスであり,平流層のオゾン層を蝕む物質である.
- 海洋のN2Oの源と沈殿所は十分に理解されていないため,正確な気候モデリングを妨げています.
- 海洋のサブボックスの領域は,N2Oサイクルのための重要だが,十分に量化されていない領域である.
研究 の 目的:
- 東部熱帯北太平洋におけるN2O減少率を直接測定する.
- 海洋のサブボキシックゾーンにおけるN2Oの循環速度を定量化するために.
- N2Oサイクルを制御する要因とその大気への排出への影響を理解する.
主な方法:
- N2Oの還元率を直接測定するために安定同位体トレーサを使用しました.
- 東部熱帯北太平洋で測定を行った.
- 環境要因との関係でN2Oサイクルの空間的分布を分析した.
主要な成果:
- サブボックスの地域におけるN2Oサイクルの割合は,不完全な脱窒化による現在のモデル予測よりも数桁高いことが判明しました.
- N2Oサイクルの速度は,有機炭素と溶解酸素濃度に強い依存を示した.
- N2Oの流通量は,大気への排出量の20倍以上で,海洋における重要な処理を意味する.
結論:
- 海洋のN2O循環は,現在のモデルでは,特にサブボックスの環境では著しく過小評価されています.
- 急速なサイクリングと環境要因への依存は,サブボキシクゾーンの拡大がN2O排出量を増加させることを示唆しています.
- 海洋のN2Oの流れを正確に定量化することは,将来の気候変動とオゾン層の減少を予測するために極めて重要です.
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