Field measurements carried out over 4 years made it possible to establish previously unknown features of the thermohaline fields and circulation of Lake Issyk-Kul. The most detailed salinity distribution maps for the entire history of observations were constructed. An area of slightly increased salinity was found in the central part of the lake, the specific “dipole” shape of which indicates the existence of not only a general cyclonic circulation, but also two separate gyres of a smaller, subbasin scale (which is partially confirmed by direct current velocity measurements). It has been established that, generally speaking, the salinity fields in Lake Issyk-Kul are extraordinarily conservative: its interannual and seasonal changes, as well as spatial variability throughout the lake (with the exception of estuarine regions), are usually measured only in hundredths of g kg^–1. An important result of the project is the discovery of a subsurface salinity maximum persisting from year to year at depths from 70 to 130 m. As shown on the basis of balance estimates and then confirmed by analysis of direct current velocity measurements, autumn–winter differential cooling leads to the fact that in canyons (i.e., paleoriver channels) in the eastern littoral region, a significant amount (up to 1 km³) of cold coastal waters freshened by river runoff enters the bottom layers of the central part of the lake. These waters are then mixed with the overlying more saline waters, which, in a situation where the upper layer of the lake is also desalinated by river runoff, leads to a salinity maximum at intermediate depths. Our measurements do not confirm manifestations of global warming in the form of an interdecadal temperature increase in the deeper layers of Lake Issyk-Kul, which was previously reported: the current (in 2018) temperature at a depth of 500 m exactly coincided with that noted in the 2003 measurements, namely, about 4.44°C. However, one can point to a very weak (about 0.03 g kg^–1) increase in the salinity of the bottom layer over the past 40 years.

中文翻译：

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伊塞克湖中的热盐结构和循环特征

经过4年的实地测量，有可能建立以前未知的热盐场和伊塞克湖的环流特征。绘制了整个观测历史最详细的盐度分布图。在湖中部发现盐度略有增加的区域，其特定的“偶极”形状表明不仅存在普遍的气旋环流，而且还存在两个较小的，流域规模较小的旋回（部分通过直流速度测量得到确认）。已经确定，总的来说，伊塞克湖的盐度场非常保守：它的年际和季节变化以及整个湖的空间变化（河口区域除外），^–1。该项目的重要结果是发现了地下​​盐度最大值在70至130 m的深度上逐年持续存在。如根据平衡估算所示，然后通过直流速度测量分析确认，秋冬季的差异冷却导致以下事实：东部沿海地区的峡谷（即古河道）中，有大量（最多1个）³公里河流径流增添的寒冷沿海水进入湖中部的底层。然后将这些水与上方的更多盐水混合，在湖的上层也被河流径流淡化的情况下，在中间深度导致盐度最大值。我们的测量结果并未以伊塞克湖的更深层年代际温度升高的形式证实全球变暖的迹象，此前曾报道过：目前（2018年）深度为500 m的温度与上述温度恰好吻合在2003年的测量中，即约4.44°C。但是，可以指出过去40年底层的盐度增长非常微弱（约0.03 g kg ^–1）。