Direct estimation of glacial ice meltwater discharge onto the Antarctic continental shelf using oxygen isotope measurement

2021 Fiscal Year Final Research Report

• Project/Area Number: 17H01615
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 海外学術
• Research Field: Environmental dynamic analysis
• Research Institution: Hokkaido University
• Principal Investigator: Aoki Shigeru 北海道大学, 低温科学研究所, 准教授 (80281583)
• Co-Investigator(Kenkyū-buntansha): 田村 岳史 国立極地研究所, 研究教育系, 准教授 (40451413) ; 松村 義正 東京大学, 大気海洋研究所, 助教 (70631399)
• Project Period (FY): 2017-04-01 – 2022-03-31
• Keywords: 氷床融解 / 南大洋 / 南極氷床 / 酸素同位体比

Outline of Final Research Achievements

To investigate the effect of Antarctic glacial melt on the global sea level rise and overturning circulation, we established an international observational array of oxygen isotope ratio, a special tracer which is indispensable in estimating the freshwater sources, and examined glacial meltwater fraction directly in the surrounding ocean. We identified regions of high meltwater fraction. Off Adelie Land Coast we detected an increase of meltwater fraction after the calving event of the glacial tongue after 2010. After mid-2010s, we observed a reversal of the long-term freshening tendency of the bottom layer in the Australian-Antarctic Basin, which could be attributed to a decrease in meltwater discharge in the West Antarctica. We detected poleward shift of the overall oceanic structure over the recent three decades in the same basin, which contributed to a comprehensive understanding of the spatio-temporal changes of the circum-Antarctic shelf ocean.

Free Research Field

海洋物理学

Academic Significance and Societal Importance of the Research Achievements

氷床融解成分を、水温などの代替指標等に基づくパラメター化によらず、直接的に明らかにする手法の有効性を示した。広い南極沿岸の主要な海域において統一的な評価が得られ、外洋側の海洋構造に伴う貯熱量分布との対応を一般化して捉えることができるようになった。ここ数十年で氷床への潜在的な熱輸送が増えた可能性と同時に、数十年規模の時間変動の存在も明らかになり、氷床融解の実態評価において継続的に注力すべき場所が絞られた。