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Surface and intermediate water mass exchanges between the North Pacific subtropics and tropics and its temporal changes

北太平洋副热带和热带表层水团和中间水团交换及其时间变化

基本信息

批准号：
10640418
负责人：
SUGA Toshio
金额：
$ 2.43万
依托单位：
TOHOKU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 1999
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10640418/
关键词：
North Equatorial Current North Equatorial Countercurrent North Pacific Tropical Water North Pacific Intermediate Water North Pacific Tropical Intermediate Water 137ィイD1oィエD1E repeat hydrography Hakuho Maru Cruise KH-99-1 WOCE WHP サブダクション

项目摘要

The purpose of the present study was to clarify circulation and mixing, and their temporal changes of major water masses in the subtropical/tropical boundary region, especially aiming to see inflow of anomalous subtropical water into the tropical gyre. We analyzed i) the repeat hydrographic section data in the western North Pacific, ii) the data from our own synoptic survey in the western tropical North Pacific, and iii) other available hydrography including WOCE/WHP. The main results are as follows.1. Isopycnal analysis of the data (i) and (iii) captured the low-salinity water carried by the North Equatorial Countercurrent (NECC) at about 5ィイD1oィエD1N, 200-300m and 26.5σィイD2θィエD2. This water probably originates in the northeastern subtropics and reaches to the tropics via the western boundary region. North Pacific Tropical Intermediate Water (NPTIW) was also captured as the high-salinity and low-oxygen water originated in the eastern tropics carried to the west, suffering considerable mixing with the adjacent subtropical water along its advection path.2. The CTD and ADCP data (ii) provided a "snapshot" of the flow field and the water mass distribution, which supports the view that the low-salinity water of the subtropical origin is carried into the NECC via the western boundary region. Comparison between the result #1 above and this snapshot suggests that NPTIW has little temporal variability while the low-salinity water varies associated with the NECC variability.3. The repeat hydrography (i) revealed the remarkable decadal change in North Pacific Tropical Water, which is originated in the central subtropics and carried by the North Equatorial Current. The change was caused not only by the thermohaline-forcing change in the formation region but also the dynamic-forcing change, that is the change in the wind field, resulting in the increased formation rate and the intensified gyre.

本研究的目的是阐明副热带/热带边界地区主要水团的环流和混合及其时间变化，特别是旨在了解异常副热带水流入热带环流。我们分析了i）北太平洋西部重复水文剖面数据，ii）我们自己在热带北太平洋西部的天气调查数据，iii）其他可用的水文数据，包括WOCE/WHP。主要研究结果如下：1.等密度线分析（i）和（iii）的数据捕获了由北赤道逆流（NECC）携带的低盐度水，大约在200- 300 m和26.5σ σ D1 θ D1 θ D2处。该水可能起源于东北亚热带，并通过西部边界地区到达热带。北太平洋热带中层水（NPTIW）也被捕获，因为高盐低氧的水起源于东部的热带地区，被带到西部，与邻近的副热带水沿着其平流路径发生了相当大的混合. CTD和ADCP数据（ii）提供了流场和水体分布的“快照”，这支持了亚热带起源的低盐度水通过西部边界区域进入NECC的观点。上述结果#1与此快照之间的比较表明，NPTIW几乎没有时间变化，而低盐度水的变化与NECC的变化有关。重复水文测验（i）揭示了北太平洋热带水的显著年代际变化，它起源于中亚热带，由北赤道流携带。这种变化不仅是由形成区温盐强迫的变化引起的，而且还与动力强迫的变化有关，即风场的变化，导致形成率的增加和涡旋的加强。