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由以下两部分组成。一种是利用硝酸盐氮同位素比值分析海洋表层生物活动和水混合的历史，另一种是通过精确测量营养物浓度来分析中深层水的平流和混合过程。前一项研究使用的是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，后一项研究使用的是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设氮同位素分析真空系统和营养测量自动分析仪。硝酸盐的浓度和氮同位素比图表明，在夏季，白令海的地表水与地下水的结合可能比阿拉斯加湾更快。在对中深水进行分析的基础上，精确测量了一种新的化学量N* (= [NO_3-] - 16)。[PO_4^3-] + 2.9) 0.87)对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，在普通水柱中不发生变化，但在底部沉积物或某些特殊水柱中分别因反硝化作用和固氮作用而减少和增加。通过对鄂霍次克海南部海盆区全部区域N*的详细观测发现，低N*水不仅位于可能发生反硝化作用的海底和陆坡，而且在200 ~ 400m深度之间沿低位涡度水从陆坡区渗透到中间层。这为北太平洋中间水的起源鄂霍次克中间水是最初形成于鄂霍次克海西北部大陆架区域（=低N*区域）并沿中间层水平流出的水团的机制提供了证据。少