Читать книгу Polar Exploration. A practical handbook for North and South Pole expeditions онлайн

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This process, however, is different in salt-water bodies and oceans. Cooling of the ocean surface causes the top layers of water to increase in density and therefore sink, a process which continues until the water reaches freezing point – which itself is lowered by the addition of salt (about −1.8°C for typical sea water).

As soon as salt water solidifies, the main types of ice formed are the following:

 Frazil First signs of freezing sea water, with an ‘oily’ look.

 Nilas Merging frazil, at first transparent, but soon grey and eventually white.

 First-year ice Nilas that has grown in one season up to 1.5–2m deep.

Ice flowers decorating newly born nilas

The impact of the wind over the ice and the currents under the ice makes the Arctic ice mass split open and creates ‘leads’ that represent endless hurdles for expeditioners

By the look of the ice, the following categories can be distinguished:

 Pack ice Newer ice.

 Ice floes Also known as pan ice.

 Hummocks Big piles of ice, part of a pressure ridge.