2018 Fiscal Year Final Research Report

Disosolved iron transport process and its mechanism driven by sea ice formation and melting in polar oceans

Research Project

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Project/Area Number	16K21586
Research Category	Grant-in-Aid for Young Scientists (B)
Allocation Type	Multi-year Fund
Research Field	Environmental impact assessment Environmental dynamic analysis
Research Institution	Fisheries Research and Education Agency (2018) National Institute of Polar Research (2016-2017)
Principal Investigator	Nakanowatari Takuya 国立研究開発法人水産研究・教育機構, 北海道区水産研究所, 主任研究員 (20400012)
Research Collaborator	Mitsudera Humio Nakamura Tomoyuki Uchimoto Keisuke Nishioka Jun Watanabe Eiji
Project Period (FY)	2016-04-01 – 2019-03-31
Keywords	物質循環モデル / 海氷・海洋結合モデル / 季節・経年変動 / 風成循環 / リン酸塩 / 沿岸親潮 / 潮汐混合 / オホーツク海
Outline of Final Research Achievements	By using an ice-ocean coupled model with an biogeochemical model, the transport process of dissolved iron and its variability in the subarctic North Pacific including the Sea of Okhotsk were investigated. Seasonal to interannual variability of dissolved iron and macro nutrient concentration in the Oyashio and northwestern subarctic North Pacific is controlled by the wind-driven transport from the Okhotsk Sea and the Bering Sea as well as the local transport from the subsurface layer due to winter convection. Such lateral transport process has an essential role on the determination of primary production in the subarctic North Pacific. On the other hand, the impact of sea ice formation and melting process on the primary production is limited to the Sea of Okhotsk.
Free Research Field	海洋物理学
Academic Significance and Societal Importance of the Research Achievements	これまで、北太平洋亜寒帯域における表層の鉄や栄養塩濃度の変化は、主に冬季の海面冷却による密度不安定による混合によって、下層から輸送されるいわゆる1次元的な枠組みで理解されてきた。本研究では、オホーツク海と北太平洋亜寒帯域の風成循環、及び海氷形成プロセスを考慮した3次元モデルを用いることによって、新たに水平的な栄養塩供給プロセスの重要性を明らかになった。特に、我が国周辺の親潮海域における栄養塩や鉄の輸送において、オホーツク海を起源とした風成循環場やクリル海峡周辺で卓越する潮汐混合による下層から栄養塩供給は、これらの水平的な物質輸送において本質的な役割を担うことが明らかになった。