Analysis of water mixing history in high latitude oceans using chemical tracers of the third generation

使用第三代化学示踪剂分析高纬度海洋中的水混合历史

• 批准号: 09440163
• 负责人: NAKATSUKA Takeshi
• 金额: $ 10.75万
• 依托单位: HOKKAIDO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09440163/
• 关键词: Chemical Tracer; Sea of Okhotsk; Nutrient; Nitrogen Isotope; Bering Sea; Alaska Bay; 高緯度海洋; 水塊混合; 溶存酸素; 酸素同位体比; 北部北太平洋

The research supported by this grant-in-aid mainly consists of following two parts. One is the analysis of history of the biological activity and water mixing in ocean surface layer using nitrogen isotope ratio of nitrate, and the other is the analysis of water advection and mixing processes in the intermediate and deep layers based on precise measurements of nutrient concentration. We used the surface water samples which were annually collected in Bering Sea and Alaska Bay by a merchant vessel between Japan and Canada for the former study, and the samples collected by the CTD/RMS observations which were carried out in Southern basins of the Sea of Okhotsk by Russian ship were utilized for the latter study. Most part of this grant was applied to construct the vacuum system for nitrogen isotope analysis and the auto-analyzer for nutrient measurement. The concentration & nitrogen isotopic ratio plot of nitrate suggested the possibility that, in summer, the surface water is more rapidly m … More ixed with the subsurface water in Bering Sea than in Alaska Bay. By the analysis of intermediate and deep waters based on the precise measurements of nutrients, a new chemical quantity, N* (=([NO_3-] - 16. [PO_4^3-] + 2.9) 0.87), was found to be very useful to trace the origin and mixing process of water masses. This N* is a quasi-conservative tracer which does not change in the ordinary water column, but decrease and increase by denitrification and N_2-fixation, respectively, occurring in the bottom sediment or some special water column. The detailed observation of N* in all over the Southern basin area in the Sea of Okhotsk revealed that the low N* water was not only located on the sea floor and continental slope where the denitrification probably occurs, but also penetrated from the continental slope area into the intermediate layer along the low potential vorticity water between 200 and 400m depths. This provides an evidence for the mechanism that the Okhotsk Intermediate Water, which is the origin of North Pacific Intermediate Water, is a water mass which is originally formed on the continental shelf area (= low N* region) in the northwestern of Sea of Okhotsk and horizontally flowed out along intermediate layers. Less

本次资助的研究主要包括以下两部分。一是利用硝酸盐氮同位素比分析海洋表层生物活动和水混合历史，二是根据营养盐浓度精确测量分析中深层水平流和混合过程。前者的研究使用了日本和加拿大之间的商船每年在白令海和阿拉斯加湾采集的地表水样本，后者的研究使用了俄罗斯船只在鄂霍次克海南部盆地进行的CTD/RMS观测收集的样本。这笔拨款的大部分用于建造用于氮同位素分析的真空系统和用于营养测量的自动分析仪。硝酸盐浓度和氮同位素比图表明，在夏季，白令海表层水与地下水的混合速度可能比阿拉斯加湾更快。通过对中层水和深层水的营养盐精确测量进行分析，发现一个新的化学量N* (=([NO_3-] - 16. [PO_4^3-] + 2.9) 0.87)对于追踪水团的起源和混合过程非常有用。该N*是一种准保守示踪剂，在普通水体中不发生变化，但在底部沉积物或某些特殊水体中分别通过反硝化和N_2固定而减少和增加。鄂霍次克海南部盆地全区N*的详细观测表明，低N*水不仅位于反硝化作用可能发生的海底和陆坡区域，而且还从陆坡区域沿200~400m深度的低位涡水渗入中间层。这为北太平洋中层水的起源——鄂霍次克中层水是最初形成于鄂霍次克海西北部大陆架区（=低N*区域）并沿中间层水平流出的水团提供了依据。较少的