Imagine you are diving in the winter season and you see a huge accumulation of ice in front of you. At first glance, it may seem that these are just fragments of an ice floe, and in general, what could be interesting in this? The paradox is that the ice does not float and does not melt, while being in the water for a long time.
The history of the study of bottom ice has an unusual past, because the debate about this phenomenon has been going on for more than a hundred years. The point of departure in identifying the nature of the bottom ice was the fact that it causes significant damage to the water supply system, as well as hydraulic power plants.
In 1914, Petrograd was left without water due to freezing of the tips of the water intake pipes.
How can ice freeze under water when its temperature is positive?
Key phrase:
At the moment of bottom ice formation, the water has a negative temperature
That's the whole secret - if you cool water intensively by stirring, then its temperature will be below zero. For this "phenomenon" to occur, a deviation of even one thousandth of a degree is enough. Small particles that have entered the water from the atmosphere are overgrown with ice, then, as they sink, they, like a snowball, begin to crystallize, forming large ice crystals (bottom ice does not always form from the surface, the presence of a seed in the form of particles suspended in water can also contribute the formation of ice, but already from the bottom).
As a result, we have several basic conditions for the formation of bottom ice in nature:
Promotional video:
Minus temperature outside - from about -10 ° C
Open water surface - will increase the heat loss of water and provide hypothermia
Strong flow of water - maintains a supercooled state of water and prevents the formation of a crust of ice on the surface
A seed - without it, the ice simply has nothing to grow on (note, almost all the ice in the video “grows” on something, and not by itself)
Where can this phenomenon be observed?
Decent frosts and fast-running rivers - all of Siberia fits this description perfectly. Here bottom ice can be observed from year to year (for example, on the Angara River). Curiously, not every area can boast of this phenomenon. For example, in Scotland, the average annual temperature of which does not differ much from the Siberian one, the freezing of hydraulic equipment from the bottom of the reservoir was observed only once.