Hot water lake is located inantarcticThe "oasis" of the ice field (generally referring to 2% of the Antarctic land covered with ice and snow all the year round), there is a layer of clear and bright fresh water on the lake surface.
Chinese name
Hot water lake
Foreign name
Hot water lake
Features
There is a layer of clear and bright fresh water on the lake
Fanda Lake is very famous because the lake hiding in the snow free dry valley of Antarctica is a hot water lake.At the bottom of the 68.6m deep lake, the water temperature is as high as 25 ℃.Known as the "white continent", Antarctica is the coldest region on the earth. There is a lot of ice and snow all the year round. 95% of the continent is covered by an ice layer up to 2000 meters thick, and the average temperature is as low as tens of degrees below zero.However, the lake found in the Antarctic dry valley is deep in the boundless ice field with its incredible temperature.This has aroused great interest of scientists and also brought a series of difficult puzzles.
Main features
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The deepest part of Fanda Lake is nearly 70 meters. There is a layer of ice 4 meters thick on the lake surface. The water temperature in the lake under the ice layer is about 0 ℃. The water temperature rises to 7.7 ℃ at a depth of 15~16 meters, and rises slowly below 40 meters.At 50 meters, the increase suddenly intensified. At 68.6 meters, the water temperature reached 25 ℃, which was equivalent to the surface seawater temperature in the East China Sea in summer.The deeper it is, the higher the water temperature is, and the lake water is light and salty.There is a layer of ice 4 meters thick frozen on the surface of the lake. The water under the ice is clear, with few plankton. The salinity of the lake water increases with the depth, forming a stratified phenomenon.The salt content of lake bottom water is often 10 times higher than that of seawater, and the calcium chloride content is even higher, 18 times higher than that of seawater.
Genetic study
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Once these strange phenomena were revealed, they aroused great interest of scientists.Some opinionated scientists think this 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 more observations, all with the same results.This gave a powerful blow to the accidental and observational fallacies.
Once the facts have been confirmed, the important question is to explain them.For this reason, the Antarctic expeditions of New Zealand, the United States, Japan and the United Kingdom have explained it from different perspectives and have been arguing endlessly.Among them, there are two views that people quite agree with, one is the solar radiation theory, the other is the geothermal activity theory.
Solar radiation theory
According to the solar radiation theory, the Antarctic summer sunshine lasts for a long time, and the lake receives more solar radiation energy, which causes the lake water temperature to rise.However, the density of lake water increases due to the increase of freezing salinity in winter.Therefore, even when the water temperature rises in summer, the density of surface water still maintains a large value, leading to the sinking of warm surface water, thus making the temperature of bottom water higher.Opponents believe that the Antarctic summer sunshine lasts for a long time, but the weather is gloomy all day long, and the solar radiation reaching the ground is still weak. In addition, the ice surface reflects more than 90% of the radiant energy, and the radiant energy reaching the ground is less, so it is impossible to raise the surface water temperature very high.Moreover, after the warm water sinks, the water temperature of the whole water layer will inevitably rise, but not just the bottom water temperature.In this way, the solar radiation theory is difficult to establish, so the geothermal theory gradually prevails.[1]
Geothermal activity theory
According to the geothermal activity theory, Vanda Lake is 50 kilometers away from the Ross Sea, and there are active Merben Volcano and the currently erupting Erebus Volcano near the Ross Sea, indicating that the underground magma activity in this area is intense,MagmaThe upwelling phenomenon is serious. Affected by the geothermal energy, the temperature of the lake water will be cold at the top and hot at the bottom.This explanation is very intuitive and easy to accept.However, after the implementation of the International Antarctic Dry Valley Drilling Program, people learned that there was no geothermal activity in the Wright Dry Valley where Fanda Lake is located, which completely denied the theory of geothermal activity.In this way, the theory of solar radiation will rise again.
American scholar Wilson and Japanese scholar Niaoji Tieya are also the main school of solar radiation theory.After years of research, they put forward new arguments, thus gaining more support.
They believe that although the sunshine duration in Antarctic summer is very long, due to the gloomy weather all day long and the strong reflection of the ice surface, the solar radiation energy received by the ground is really poor.However, ice has a certain transparency and a certain transmittance to sunlight, so the ice layer below the surface will more or less obtain the energy of solar radiation.In addition, the local wind is strong, and the snow is blown away by the wind in winter. The snow layer is very thin, mostly exposed rocks, which makes the ground absorb more heat in summer and the climate is warmer.Over the years, the temperature of the ice layer on the surface and below will rise and finally reach the point of melting.Due to the high salinity and density of the bottom layer, the bottom water will not rise to the surface layer. As a result, the high temperature characteristics will be retained.At the same time, the surface layer loses heat in winter, and the bottom layer relies on the protection of the upper layer, so the heat loss is small, so the bottom water temperature is extremely high.Recently, scientists have observed that the water temperature in the bottom layer has a trend of slowly rising, and found that salt solutions such as calcium chloride can effectively accumulate solar heat, providing a favorable basis for this theory.[2]
