Stability in Hypolimnion of Deep Rift Lkes, East Africa

东非深裂谷的 Hypolimnion 稳定性

• 批准号: 02041001
• 负责人: NAKAO Kinshiro
• 金额: $ 3.2万
• 依托单位: Hokkaido University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for international Scientific Research
• 财政年份: 1990
• 资助国家: 日本
• 起止时间: 1990 至 无数据
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-02041001/
• 关键词: Hypolimnion; Meromictic vertical profiles; Dissolved gases of carbon dioxide; Dissolved gases of methane; Stable stagnant layer; Tropical lakes; Thermohaline convection; Internal seiche

Lake Kivu is situated in the equatorial region of the Rift Valley, East Africa, at latitude 2^ﾟS and longitude 29^ﾟE ; it discharges from the south end of the lake by the Ruzizi River into Lake Tanganyika. The lake basin is characterized by a tectonic unit separated from the Edward-Kivu Trough by active volcanoes including Mt. Nyamulagira, Mt. Nyiragongo and others. Formed by ponding which occurred by lava flows across the valley, the lake is deep and shows a submerged shoreline like a rias coast, reflecting the damming effect.The lake is classified as a tropical lake from the thermal regime, and has by far the most meromictic vertical profiles of water temperature. Its morphometric features are : 2,300Km^2 in area of lake surface, 7,300Km^2 in basin area including the lake surface, 485m in maximum depth and240m in mean depth.The sounding results of water temperature indicate the significant tendency of rising from the depth of 90m to the bottom at all sites, it is characterized that t … More he density of lake water is increased by a dissolved matter and is meromictic. The water of lake Kivu has been stabilized by a slight increase, with increasing depth, in the amounts of dissolved gases of methane and carbon dioxide.The points to which special attention should be paid to the profiles of temperature and conductivity obtained by sounding responses in Lake Kivu, are two convection layers in the hypolimnion shown vertically with the same values. It is pointed out that these convection layers have the step-like structure similar to a thermohaline convection.In the case of a thermohaline convection, the spreading perturbations originate in a great difference between the molecular diffusivity of salt and temperature. But that of Lake Kivu is caused by a decrease in solubility in dissolved gases accompanying uplifting of water. It is satisfactory to consider that an internal wave and a sudden gas eruption from the bottom work as trigger of starting perturbation in the hypolimnion. Less

基伍湖位于东非裂谷的赤道地区，南纬2度，东经29度，从湖的南端经鲁齐齐河流入坦噶尼喀湖。湖盆的特点是一个构造单元从爱德华基伍海槽分离的活火山，包括山。尼亚穆拉吉拉山尼拉贡戈和其他人。该湖是由熔岩流流经山谷形成的积水形成的，湖水很深，呈现出像rias海岸一样的淹没岸线，反映了筑坝效应。从热状况来看，该湖被归类为热带湖泊，并且具有迄今为止最多的水温垂直剖面。其地貌特征为：湖面面积2,300平方公里，包括湖面在内的盆地面积7,300平方公里，最大水深485米，平均水深240米。水温测深结果表明，各站水温从90米以下向湖底有明显的上升趋势，其特点是： ...更多信息 湖水的密度因溶解物质而增加，是部分混合的。基伍湖的水已经稳定的略有增加，随着深度的增加，在甲烷和二氧化碳的溶解气体的量。应特别注意的点，在基伍湖的测深响应得到的温度和电导率的配置文件，是两个对流层在垂直示出具有相同的值。指出这些对流层具有类似于温盐对流的台阶状结构，在温盐对流的情况下，扩散扰动源于盐分子扩散系数与温度之间的巨大差异。但基伍湖的水上升是由于溶解气体的溶解度下降造成的。认为内波和海底气体突然喷发是引起低层扰动的触发器是令人满意的。少

项目成果

中尾 欣四郎: "Stability in hypolimnion of Lake Kivu, East Africa" Journal of the Faculty of Sciene,Hokkaido University. 9ー2. (1992)

Kinshiro Nakao：“东非基伍湖低水位的稳定性”北海道大学学报 9-2。

Kinshiro Nakao: "Stability in hypolimnion of Lake Kivu, East Africa" Journal of the Faculty of Science, Hokkaido University. 9-2. 1992

Kinshiro Nakao：“东非基伍湖低水温的稳定性”北海道大学理学院学报。