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

目前的研究的目的是澄清循环和混合，以及其在亚热带/热带边界地区主要水质量的临时变化，特别是为了看到大量的异常亚热带水进入热带同性恋。我们分析了一）西北太平洋地区重复的水文部分数据，二）西北太平洋地区我们自己的综合调查数据，三）其他可用的水文，包括WOCE/WHP。主要结果如下：1. Isopycnal analysis of the data （i） and （iii） captured the low-salinity water carried by the North Equatorial Countercurrent （NECC） at about 5-D1o-D1N， 200- 300 m and 26.5-D2。这片水域可能起源于东北地区的亚热带，并通过西部边界地区到达热带。北太平洋热带中水（NPTIW）也被捕获为在东部热带中产生的高盐度和低氧水，将其与不利亚热带水一起混合到西部，并在其引进途径中进行有必要的混合。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。比较结果#1上的结果和本快照建议，即NPTIW在与NECC变量相关的低盐度水变化时有很小的临时变化。重复水文学（i）揭示了北太平洋热带水域中引人注目的十年变化，它起源于中央亚热带，并由北赤道电流承载。这种变化并不只是由于形成区域的热激素驱动的变化，但也是动态驱动的变化，即风场的变化、在增加的形成率和强化的同性恋中的结果。

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.