日本地球惑星科学連合2018年大会

講演情報

[EJ] ポスター発表

セッション記号 A (大気水圏科学) » A-CG 大気水圏科学複合領域・一般

[A-CG38] 北極域の科学

2018年5月24日(木) 13:45 〜 15:15 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:津滝 俊(東京大学)、漢那 直也(北海道大学 北極域研究センター)、鄭 峻介(北海道大学 北極域研究センター、共同)、中村 哲(北海道大学大学院地球環境科学研究院)

[ACG38-P17] Optical tracer method to distinguish fresh water sources in the Pacific Arctic region

*藤原 周1松岡 敦3西野 茂人1和賀 久朋2平譯 享2菊地 隆1 (1.国立研究開発法人海洋研究開発機構、2.北海道大学水産学部、3.ラバル大学タクビック国際共同研究所)

キーワード:CDOM吸収係数、太平洋側北極海、淡水分布

Recent freshening of the Arctic Ocean caused notable changes in ocean environment and circulations. Both increases in sea ice melt water and river discharge are known to have a large effect on the freshening. Chemical tracers, oxygen isotope ratio and total alkalinity (TA), are used to distinguish fresh water sources to understand their contribution to the freshening and distribution of the water masses. However, estimation of fresh water sources using chemical tracers has a disadvantage in high frequent sampling, because it takes considerable time to measure. In this study, we propose a method to discriminate water sources using absorption of CDOM (aCDOM) for the Pacific Arctic region.
We obtained salinity, TA, and aCDOM at 443 nm (aCDOM(443)) from the seven cruises of R/V Mirai conducted in the Pacific Arctic region during late summer. Fraction of sea ice melt water (fSIM) and other fresh water (fOF) were calculated from their known end-member values of salinity and TA. We identified aCDOM(443) end-member values of fSIM and fOF, which were unknown, applying a least-square method to the relationship between fresh water fraction and aCDOM(443). Thus, fSIM and fOF became retrievable from salinity and aCDOM(443) instead of TA. We also evaluated the accuracy of the optical tracer method comparing fresh water fraction values calculated from chemical and optical tracers, and obtained equivalent results to the chemical tracer method. Estimation of fresh water sources with higher frequent monitoring using aCDOM might advance the comprehension of ocean circulation and related chemical- and biological system in the Arctic.