Why is the hot water lake always hot?

There are two views that people quite agree with, one is the theory of solar radiation, and the other is the theory of geothermal activity.

Brief introduction of hot water lake

American satellites have discovered a huge "lake" that humans have never seen before in the Weddell Sea off the coast of Antarctica in the South Atlantic. This mysterious lake has been shown in the satellite photos of 1973. It appears in most winters, but sometimes it flashes. Antarctica, known as the "white continent", is the coldest region on earth. It is covered with snow and ice all the year round. 95% of the mainland is covered with ice as thick as 2000 meters, and the average temperature is as low as tens of degrees below zero. However, this lake, discovered in the dry valley of Antarctica, is deeply immersed in the vast ice sheet at its incredible temperature, which brings a series of mysteries to polar exploration and scientists.

This lake is called Fanda Lake. 1960, Japanese scholar Tie also analyzed the measured data and found that the water temperature under the thin ice layer on the lake was about 0℃. With the increase of depth, the water temperature keeps rising. 15-16m depth, the water temperature rises to 7.7℃, below 40m, and the water temperature rises slowly. At 50 meters, the increase suddenly intensified. From the bottom of the lake to 68.8 meters, the water temperature is as high as 25℃, which is almost the same as the surface water temperature in the East China Sea in summer. Moreover, the salt content of the bottom layer is more than 6 times that of seawater, especially the calcium chloride content is abnormally high, which is about 18 times that of seawater.

Once these strange phenomena were disclosed, they aroused great interest of scientists. Some opinionated scientists think it is incredible and think it may be caused by observation errors or some accidental factors. In order to verify the reliability of the above observations, scientists have made many observations and obtained the same results. This gives a powerful blow to accident and observation error theorists.

Cause exploration

Now that the fact has been proved, the important question is to explain it. To this end, the Antarctic expeditions of New Zealand, the United States, Japan and the United Kingdom elaborated from different angles and debated endlessly. There are two views that people quite agree with, one is the theory of solar radiation, and the other is the theory of geothermal activity.

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.

Geothermal activity

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.

American scholar Wilson and Japanese scholar torii Tieno are also the main schools of solar radiation theory. After years of research, they put forward new arguments and won the support of more people.

They believe that although the summer sunshine in Antarctica is very long, the solar radiation energy received by the ground is really pitiful due to the gloomy weather and the strong reflection of the ice. But ice is transparent to sunlight, so the ice below the surface will get more or less the energy radiated by the sun. In addition, the wind is strong, the snow is blown away by the wind in winter, and the snow layer is very thin, mostly bare rocks, which makes the ground absorb more heat in summer and the climate is warmer. Over the years, the temperature of the surface and the ice below will rise and eventually melt. Because of the high salinity and density of the bottom layer, the bottom water will not rise to the surface layer, and the result is that the characteristics of high temperature are preserved. At the same time, the surface layer loses heat in winter, and the bottom layer relies on the protection of the upper water layer, so the heat loss is less, so the water temperature at the bottom layer is extremely high. Recently, scientists have observed that the bottom water temperature is rising slowly, and found that salt solutions such as calcium chloride can effectively accumulate solar heat, which provides a favorable basis for this theory.