What is a polynya? Causes of the appearance of ice gaps

How many people know about what a polynya (do not need to be confused with a plant wormwood)? In fact, this is a very curious question. After all, despite the fact that every person encountered 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 a polynya?

Polynye is not a freezing window on the surface of the reservoir. 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 such a physical phenomenon can be observed both in flowing and in standing waters.

We hope, after the above, it becomes more or less clear what a polynya is. However, one more important point should not be overlooked. Namely, what the polynyas is called as gaps in the whole cover of ice, and holes on drifting ice floes.

Why are polynyas formed?

The largest accumulation of ice gaps can be observed on rivers with a high flow velocity. In such conditions, water simply does not have time to freeze and turn into a hard crust. Also polynyas are formed in places where the release of warmer waters occurs. It can be, for example, industrial drains, underground keys, sources and so on.

The sailors who are floating in the northern waters are well aware of what such a polynya is. They can often observe this phenomenon in places where a strong wind splits drifting ice in half.

Why does the polynya not freeze?

To begin with, in places where warm waters approach the surface, the polynyas can not simply disappear. Because of the 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 coming of dawn, the wind rises, which instantly destroys the ice cover. The influence of the wind is not amenable only to those areas that are near the shore, or enclosed by a certain barrier.