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Study on the distributions of Th-234 and biological production in the open ocean

公海Th-234分布及生物生产研究

基本信息

批准号：
10640475
负责人：
TAGUCHI Kazunori
金额：
$ 2.11万
依托单位：
Mie 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 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10640475/
关键词：
thorium-234 primary production scavenging oligotorophic ocean chlorophyll α 地形湧昇

项目摘要

Observation results repeatedly done at a station of the Shikoku Basin mid latitude showed that ^<234>Th in seawaters were nearly equilibrium with its parent nuclide ^<238>U during the ocean stratified. This means that this area is located in the subtropical regions and belongs to the oligotorophic regimes having few particulate fluxes. On the other hand, a profile of distinct disequilibrium of ^<234>Th against ^<238>U was found during the winter cruise in December 1999. Through these observations, the significant deficiency of ^<234>Th was always found in the subsurface layer of chlorophyll α maximum even in summer. Therefore, it shows that the particulate removal process does surely work there. Some continuous biological activities are considered to usually exist in the bottom of euphotic zone where nutrients are fueled up from deep waters.However, chlorophyll α inventories were not always related to ^<234>Th deficiency. For instance, ^<234>Th deficiency was small in June 2000 when the high amount of integrated chlorophyll α was observed, and it was large in December 1999 when the approximately half amount of chlorophyll α of June. Though the issue of this decoupling is not irrelevant to the difference of retention time in seawaters between two parameters, it seems that the low productivity in this region dependent on the enhanced production by some pulsant events causes to amplify that. In case of winter, relative high chlorophyll α was widely distributed in the upper waters, and such a pattern looked like that of ^<234>Th deficiency. As this pattern is largely different from that in summer having the peaked subsurface maximum, it is suggested that ^<234>Th deficiency profiles are influenced by the productive structure ascribed to the physical mixing in winter waters. Therefore, these things mean that one shot observation is not always effective on the annual biological production of oligotorophic oceans.

四国海盆中纬度某站的重复观测结果表明，在海洋分层过程中，<234>海水中的^ Th与其母核素^ U接近平衡<238>。这意味着该地区位于亚热带地区，属于寡地形区，颗粒物通量很少。另一方面，<234><238>在1999年12月的冬季巡航中发现了^ Th对^ U的明显不平衡剖面。通过这些观测发现，<234>即使在夏季，叶绿素α最大值的次表层也始终存在明显的~（13）Th亏缺。因此，它表明颗粒去除过程确实在那里起作用。真光层底部通常存在一些连续的生物活动，因为那里的营养盐是从深层沃茨中补充上来的，但叶绿素α含量并不总是与<234>Th缺乏有关。如<234>2000年6月叶绿素α含量较高时，Th亏缺较小; 1999年12月叶绿素α含量约为6月的一半时，Th亏缺较大。虽然这种脱钩的问题是不相关的两个参数之间的海水中的保留时间的差异，它似乎是在这个地区的低生产力依赖于一些不稳定事件的提高生产的原因放大。冬季较高的叶绿素α广泛分布于上层沃茨，类似于<234>Th缺乏的模式。由于这种模式是在很大程度上不同于在夏季有峰值的次表层最大值，这表明，^<234>Th缺乏剖面的影响归因于在冬季沃茨的物理混合的生产结构。因此，这些事情意味着一次观测并不总是有效的每年生物生产的寡托罗夫海洋。