A study of predictabiliy of marine ecosystem in the Arctic Ocean and its adjucent regions based on an ice-ocean coupled data assimilation system

2021 Fiscal Year Final Research Report

• Project/Area Number: 17KK0014
• Research Category: Fund for the Promotion of Joint International Research (Fostering Joint International Research)
• Allocation Type: Multi-year Fund
• Research Field: Environmental impact assessment
• Research Institution: Fisheries Research and Education Agency (2018-2021); National Institute of Polar Research (2017)
• Principal Investigator: Nakanowatari Takuya 国立研究開発法人水産研究・教育機構, 水産資源研究所(釧路), 主任研究員 (20400012)
• Project Period (FY): 2018 – 2021
• Keywords: 海氷 / 北極海 / オホーツク海 / 低次生態系モデル / 予測可能性 / データ同化 / 気候変動 / HNLC

Outline of Final Research Achievements

We evaluated the impact of medium-range to decadal time-scale atmospheric variability on the primary production in polar oceans and its adjacent regions by using numerical model simulations based on an ice-ocean coupled low-trophic level ecosystem model and the technique of data assimilation. In the Arctic Ocean, we found that synoptic-scale meteorological fluctuation has the significant impact on the enhancement of primary production in sea ice melting season through the vertical mixing process and the resultant nutrient-rich water supply to the surface. In the Sea of Okhotsk, accompanied with the sea ice decline, the primary production in spring season has increased for the past 37 years due to the improvement of light availability. On the other hand, the primary production has decreased in the subarctic North Pacific by the combination effects of the weakening of thermohaline circulation in the Sea of Okhotsk and the wind-driven ocean circulation in the subarctic North Pacific.

Free Research Field

海洋物理学

Academic Significance and Societal Importance of the Research Achievements

従来、地球温暖化をはじめとする気候変動に対する海洋低次生態系への影響が指摘されているが、その変動要因やその将来予測については未解明な部分が多い。本研究では、高解像度の海氷・海洋結合低次生態系モデルを用いた数値実験によって、大気によって励起される海洋表層の混合や風成循環の変化が基礎生産量の変動において実施的なインパクトを持つことを明らかにした。特に、北太平洋亜寒帯域では、黒潮続流からの高塩分水の輸送量の増加が冬季海洋混合層の深化をもたらし、光環境の悪化を通して春季ブルームの遅延をもたらすことが示された。これらの結果は、海洋低次生態系の近未来将来予測には気温だけでなく風の変化の重要性を提示する。