Polynya

As a polynya (also: polynya, Polynia ) refers to a large open water or thin ice layer in the Arctic or Antarctic sea ice, which can reach an area of ​​several thousand square kilometers. The term derives from the word полынья [ pʌɫɨɲja ], the ice-free areas on any otherwise frozen waters in the Russian language - even Waken on rivers and lakes - called.

Polynyas (plural also: polynyas, Polynjen, polynyas ) are generally formed by wind action, tidal or rising warm sea water. You can often over long periods of time, remain possibly exist over the years and because of their influence on ocean currents, marine biology and climate subject of polar research. According to their point of origin three types of polynyas are distinguished: Küstenpolynjas (Coastal or Shore polynyas ), polynyas, which are limited by fast ice ( Flaw polynyas ) and coastal polynyas remote (Open -Ocean polynyas ).

Küstenpolynjas (Coastal or Shore polynyas )

Küstenpolynjas arise when strong offshore katabatic winds drift away from the mainland newly formed ice from the coast. This leads to the ice-free zones between the pack ice and the land ice that may be 50 to 100 miles wide. Küstenpolynjas are so-called " ice factories ": The wind drives the sea ice away from the coast and sets the water again from the cooling earth's atmosphere until it freezes. The resulting ice expels wind from the coast.

Polynyas, which are limited by fast ice ( Flaw polynyas )

Polynyas can also occur on fast ice. They are wind- induced normally. This pack ice is advected by winds from the Festeisgrenze. This process takes place in winter, usually several times repeatedly at the same locations in the Arctic shelf seas instead. One example is the Polynjen occurring in the Laptev Sea before Northeast Siberia. Because of the Arctic Ocean sea ice crucial contributing production ( the sea ice formed in the Polynjen is transported by the Trans Polar Drift Arctic Ocean ), they are part of many research work.

Coastal polynyas distance (Open -Ocean - polynyas )

Far from the coast to develop so-called "Open -Ocean - polynyas ". They probably arise from the fact that warmer deep water is diverted through surveys of the seabed ( seamounts, even at great depths ) to the surface and the ice starts to melt from the bottom. The most famous -coast polynya in the Southern Ocean was the Weddell polynya that occurred in three consecutive years ( 1974-76 ) in the Weddell Sea and their largest dimension about 1000 amounted to 350 kilometers. Polynyas are of comparable size and the appropriate distance from the coast were not observed in the Arctic Ocean long, but in August 2006 was a great polynya in the Beaufort Sea.

Impact and importance

Polynyas play a significant role in the formation of cold, dense Antarctic Bottom Water ( AABW ), which is distributed in all oceans as the bottom water layer. Due to the cooling of the water and the constant formation of sea ice - which is still only contains very little salt - creates a very cold, salty and therefore dense water that sinks to great depths.

In polynyas is often the phenomenon of " Arctic Seerauches " observed rising from the open water in the much colder ambient air. This is a sign that the sea much heat is released into the atmosphere.

In addition to the formation of deep-water polynyas are of great importance for the characters appearing in the Antarctic and Arctic creatures. Holes in the ice are essential for mammals such as seals and whales that need air to breathe. In addition, (phytoplankton ) grow better than under the ice, because ( in the polar summer) more light is available here microscopic algae. From phytoplankton to small crustaceans ( krill, Euphausia superba ), which in turn are the main food for whales and other animals feed.

Theory of the ice-free Arctic Ocean

→ Main article: Theory of the ice-free Arctic Ocean

The observations of polynyas by the polar explorer Elisha Kent Kane, Isaac Israel Hayes and George De Long may have been the reason why scientists believed the mid-19th century to an ice-free zone around the North Pole. Only an expedition of George Nares ( 1872-76 ) could refute this thesis clearly.