Incorporation of particulate matters into sea ice: a key factor of material cycle in polar oceans

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K23370
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 1101:Environmental analyses and evaluation, environmental conservation measure and related fields
• Research Institution: National Institute of Polar Research (2021); Japan Agency for Marine-Earth Science and Technology (2020)
• Principal Investigator: ITO MASATO 国立極地研究所, 研究教育系, 特任研究員 (40887907)
• Project Period (FY): 2020-09-11 – 2022-03-31
• Keywords: 海氷 / 氷晶 / 物質循環

Outline of Final Research Achievements

Underwater interaction between frazil ice (newly formed ice) and seafloor sediment is considered to be a major process to supply particulate matter with sea ice, according to past laboratory studies. In this study, the mooring data obtained in the Sea of Okhotsk were analyzed in order to examine the penetrate-depth of frazil ice in a real ocean. This study revealed that the penetrate-depth was 35 m averagely under windy conditions (wind speed > 8 m/s) although its maximum reached 100 m. This result indicates the possibility that sea ice mainly incorporates particulate matter through the interaction between frazil ice and resuspended seafloor sediment in coastal polynyas, which are the high ice production areas distributed in shallow coastal regions in polar oceans.

Free Research Field

海氷物理

Academic Significance and Societal Importance of the Research Achievements

春に海氷が融けると海氷内の物質は海へと供給される。この過程は海氷域で春季に一般的に生じる植物プランクトンの大増殖を引き起こす要因と考えられている。しかし、海氷内の物質の起源やその海氷による取り込み過程は未解明である。本研究では、この過程で重要視されている氷晶に関して、海洋中での生成が起こる状況やその存在深度を現場観測から初めて明らかにした。これらの結果から、海氷による物質の取り込みが浅い沿岸域での氷晶と再懸濁物の接触を通じて生じることが示唆される。また、極域海洋の生物生産が、海氷から海洋へと供給される海底堆積物由来の物質に強く依存する可能性が示唆される。