Why is Antarctic Warm Water Lake warm? Seek an answer

According to the theory of solar radiation, the lake in Antarctica receives more solar radiation energy because of the long sunshine time in summer, which leads to the increase of water temperature on the lake. However, due to the increase of frozen salinity in winter, the density of lake water increases. Therefore, even when the water temperature rises in summer, the density of surface water still keeps a large value, which makes the warm surface water sink, thus making the bottom water temperature higher. Opponents believe that the summer sunshine in Antarctica is long, but the weather is gloomy all day, and the solar radiation reaching the ground is still very weak. Moreover, the ice surface reflects more than 90% of the radiant energy, and the radiant energy reaching the ground is even less, so it is impossible to make the surface water temperature rise very high. Moreover, after the warm water sinks, it will inevitably increase the water temperature of the whole water layer, and it is impossible to only increase the water temperature at the bottom. In this way, it is difficult to establish the theory of solar radiation, so the geothermal theory gradually gained the upper hand. According to the theory of geothermal activity, Lake Fanda is 50 kilometers away from the Ross Sea, and there are active Merben Volcano and active Erebus Volcano near the Ross Sea, which indicates that the underground magma activity in this area is intense and the magma upwelling phenomenon is serious. Under the influence of geothermal energy, the temperature of the lake will be hot and cold. This explanation is very intuitive and easy to accept. However, after the implementation of the international Antarctic dry valley drilling plan, people learned that there was no geothermal activity in Wright dry valley where Fanda Lake was located, which completely denied the geothermal activity theory. In this way, the theory of solar radiation will rise again.