Thermograms of lakes of Bolshoy Solovetsky Island

Cultural and historic ensemble of the Solovetsky Islands is listed by UNESCO as the World Heritage Site. The Solovetsky archipelago comprises six islands in the western part of the White Sea, covering 300 km2. Population of the biggest island, Bolshoi Solovetsky, is under 1000, and about 30000 tourists visit the Iceland annually. Regular consumption of electricity is under 1,6 MW during the winter, and about 0,8 MW in the summer period. This energy is being produced by 2 diesel generators. There is no hot water supply on the island, but a part of households is connected to a district heating network consuming up to 2,6 MW (winter peak) of heat produced by 2 boilers. Some researches speak of geothermal anomaly under the Solovetsky archipelago (White sea). The hypothesis is based on studies of biocenose, which occurs to be uncharacteristic for the latitude. In 2021, Vernadsky State Geological Museum of RAS, with support of Neft-Service, ltd., has conducted series of temperature measurements in the lakes of Bolshoy Solovetsky island in order to test the hypothesis.
From a typical thermogram’s shape, all the lakes on Bolshoi Solovetsky island are of dimictic type, i.e. during a summer upper layers of water are warm, sometimes – up to 25 oC, and in the winter they get frozen. At the same time, dimictic lakes are supposed, at the depth unaffected by wind mixing and freezing, to have a corresponding with max density of water constant temperature, which is about 4 oC. In our case, all but two lakes respond to the rule. At the Bolshoye Krasnoe lake, the bottom temperature at 15-20 m depth is well over 6 oC, and at the lake Shchuch’e – 5,16-5,26 oC.
These anomalous values, theoretically, could be caused by one of 3 reasons;
• chemical reactions in the bottom sediments,
• wind mixing of the water,
• local anomaly of endogenic heat flow.
As the goal of the study is to evaluate a possibility of using geothermal resources at the island, we are interested in the 3d reason. But, to exclude the first two, additional researches have to be conducted.

In the attached file are the thermograms of 12 lakes of Bolshoy Solovetsky Island. Data was collected during the expedition in July 2021.