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.

索洛维茨基群岛文化历史建筑群已被联合国教科文组织（UNESCO）列入世界遗产（World Heritage Site）名录。索洛维茨基群岛（Solovetsky archipelago）是白海西部的六岛群岛，总面积达300平方千米。最大岛屿大索洛维茨基岛（Bolshoi Solovetsky）的常住人口不足1000人，每年约有3万名游客到访该群岛。冬季常规电力负荷低于1.6兆瓦，夏季约为0.8兆瓦，全部由2台柴油发电机供应。岛上无热水供应，但部分住户接入区域供热管网，该管网的冬季峰值热负荷可达2.6兆瓦，热源由2台锅炉提供。有研究指出，白海海域的索洛维茨基群岛下方存在地热异常。该假说基于对生物群落（biocenose）的研究——该群落的组成特征与该纬度带的典型生态群落不符。2021年，俄罗斯科学院（RAS）维尔纳茨基国家地质博物馆在Neft-Service有限公司（Neft-Service, ltd.）的支持下，针对大索洛维茨基岛的湖泊开展了一系列温度测量实验，以验证该地热异常假说。通过典型温度廓线图（thermogram）的形态特征判断，大索洛维茨基岛的所有湖泊均为双季对流型湖泊（dimictic type）：夏季表层水温升高，最高可达25℃，冬季则完全封冻。通常而言，双季对流型湖泊在不受风力混合与冰冻影响的深层水域，水温应维持在水体密度最大的恒定温度——约4℃。但本次观测中，除两座湖泊外，其余湖泊均符合这一规律。其中大红色湖（Bolshoye Krasnoe lake）15-20米深度的水底水温远超6℃，舒奇耶湖（Shchuch’e lake）的水底水温则为5.16-5.26℃。理论上，这类异常水温可能由三种原因导致：① 底泥中的化学反应；② 水体的风力混合作用；③ 内生热流（endogenic heat flow）局部异常。本研究的目标是评估该岛屿开发地热资源的可行性，因此我们重点关注第三种成因。但为排除前两种可能性，仍需开展补充研究。本附件包含大索洛维茨基岛12座湖泊的温度廓线图数据，相关数据采集于2021年7月的科考考察活动中。