Departmental Bulletin Paper アムール川の流出水はオホーツク海北西陸棚域でどのように振る舞うのか?

馬目, 馬目  ,  三寺, 史夫  ,  Wang, Jia  ,  若土, 正暁

74pp.55 - 65 , 2016-03-31 , 低温科学第74巻編集委員会
アムール川流出水の振舞いは,鉄輸送におけるその重要性にもかかわらず未知の部分が多い.本研 究ではオホーツク海北部における海氷-海洋結合シミュレーションを行い,「アムール川流出水が高密 度陸棚水の経路に物質を輸送しうる」という仮説を検証した.シミュレーションの結果,陸棚域で 100 km 以上沖へ流出水を輸送しうる二つの経路を確認した.これらの経路は河川水,高密度陸棚水, 西向きの季節風が力学的にバランスすることにより維持される.回転流体系では通常河川水は岸沿い を流れるが,本研究はこうしたユニークな結合効果が流出水を効率的に沖側へと運び,高密度陸棚水 の経路へ鉄を含む物質を堆積しうることを示した.The paths of the Amur River discharge on the continental shelf in the Sea of Okhotsk are still unknown despite their significance in transporting dissolved and particulate iron. In this study, we conduct a coupled ice-ocean simulation for the northern Sea of Okhotsk from June 1998 to September 2000 to answer the question: Does the Amur River discharge deposit materials to the pathway of the dense shelf water? In a series of numerical experiments, we identified two routes (the western and eastern routes) that could transport the river water more than 100 km offshore over the northwestern continental shelf. The two routes share the clockwise gyre in the Sakhalin Gulf and the northeastward flow on the northwestern continental shelf. These features are connected through the westward jet along the slope from the Sakhalin Gulf (the western route) and the northward transport over the shelf break canyon (the eastern route). The river water, the dense shelf water, and the easterly wind are in a fine geophysical balance for those features, and all are required for the formation of the two routes. The model results show that these unique joint effects in the Sea of Okhotsk allow the Amur River discharge to be effectively transported over the northwestern continental shelf, unlike a general river discharge that flows along the coast, and deposit materials into the pathway of the dense shelf water.

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