How many people know about what is polynya (not to be confused with polynya plant)? In fact, this is a very interesting question. Indeed, despite the fact that every person came across this phenomenon in real life, only a few know about its true nature. And therefore let's dwell on it in more detail.
What is polynya?
Polynya is a non-freezing window on the surface of a pond. It represents a hole in the middle of the ice cover, which does not drag out even in the most severe frosts. It should be noted that a similar physical phenomenon can be observed both in flowing and standing waters.
Hopefully, after the above, it becomes more or less clear what is polynya. However, one more important point should not be overlooked. Namely, what the polynyas call both the gaps in the whole ice cover, and the holes on the drifting ice floes.
Why polynyas are formed?
The greatest accumulation of ice gaps can be observed on rivers with a high flow velocity. In such conditions, the water simply does not have time to freeze and turn into a hard crust. Polynyas are also formed in places where warmer waters are released. This may be, for example, industrial gutters, underground keys, sources, and so on.
The fact that such a polynya, well-known sailors, floating in the northern waters. They can often observe this phenomenon in places where a strong wind splits the drifting ice floes in half.
Why does the polynya not freeze?
Let's start with the fact that in those places where warm water rises to the surface, the polynya simply cannot disappear. After all, due to temperature drops, the ice melts instantly, forming an empty window.
If we talk about deep rivers or reservoirs, then things are different. There at night a thin ice crust forms on the surface of the water. With the arrival of dawn, the wind rises, which instantly destroys the ice cover. Only those areas that are near the coast, or enclosed by a kind of barrier, cannot be affected by the wind.