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= Polynya's - Important to Polar Bears, the Arctic and the World: The Case of the Polar Bear =

A polynya is an area of open water surrounded by sea ice. It is now used as geographical term for areas of sea in Arctic or Antarctic regions which remain unfrozen for much of the year. These areas are usually presistent (lasting for 9-10 months) and vary in size from less than a few square kilometers to over 50,000 square kilometers! [**Source**: http://www2.fsg.ulaval.ca/giroq/now/what.htm]. The water remains open in a polynya due to processes that prevent sea ice from forming or that quickly move sea ice out of the region. There are two kinds of polynyas and coastal and, both of which are different only by the their mechanism of ice removal. [**Source**: http://nsidc.org/seaice/characteristics/polynyas.html] In the Arctic, polynyas are found within >2 m thick ice packs that cover the Arctic Ocean and in adjacent seas.  The figure above show the difference between the coastal and open polynyas. Coastal polynyas form from latent heat and vertical mixing processes while open ocean polynyas form from sensible heat and stratification processes.

Polynyas are important for several reasons:


 * //They are a source of heat and moisture to the atmosphere, so they modify the weather in surrounding areas.//
 * //They are sources of ocean bottom water.//
 * //Important resources for wildlife - they provide access between the ocean and atmosphere for a variety of animals, including seals and penguins.//
 * //Because polynyas persist for long time periods and because overturning ocean water brings nutrients to the surface,// //phytoplankton thrive in polynyas.//
 * //Polynyas are important breathing and feeding areas for wintering or migrating marine mammals and birds.//

[Source: http://nsidc.org/seaice/characteristics/polynyas.html]



The above figure is a sketch of the Antarctic coast with glaciological and oceanographic processes



The figure above shows where most of the Arctic polynyas are located [**Source**: http://www2.fsg.ulaval.ca/giroq/now/what.htm]

In Canada, we have the "North Water Polynyas" that occurs seasonally, at the same time and place each year. Animals, such as the polar bear, adapt their life strategies to the regularity of the polynyas. In fact, these areas keep walruses, narwhales and belugas from migrating south and in the spring, the thin sea ice covering the polynyas lets light in thus allowing photosynthesis to occur. Microalgae, the basis of the arctic food chain, take full advantage of the polynyas by blooming. Planktonic herbivores feast on this bloom and soon become food for cod, seals and whales. We all know that polar bears rely on seals, in fact, they have been known to swim up to 65 km across the open water of a polynya in order to find food.



The above figure shows a basic Arctic food-web layout. Notice how everything is connected. that the survival of the polar bear depends in large part on the accessibility to its preferred food item, the seal.


 * The problem in relation to polar bears**

A disruption in the timing and creation of polynyas as well as, in their size and persistence, is having a detrimental effect on polar bear survival. Because polar bears heavily utilize ice cracks called "Leads" and "Polynyas" for their hunting potential, the shrinking of polar ice due to global warming and/or changes in sun insolation patterns is negatively affecting these hunting grounds. Polar bears spend greater time roaming and waiting for prey that doesn't show. As the ice melts back the area for hunting decreases so polar bears too are weakening, shrinking back. On top of that, the numerous and complex changes that are occuring within the polynyas has become incredibly variable. So variable in fact, that polar bears can no longer rely on changing environmental cues and patterns to adapt fast enough and survive. Many end up starving on ice floes while they wait for prey; others become desperate and either turn to cannibalism or venture into small towns and become nuisances in their attempt to find food. These starving animals moving into human populated areas give the impression that the polar bear population is healthy and vibrant but really it is a dramatic showing of just how desperate these bears have become for food. Hunters see the polar bears population as falsely increasing and so bag limits, at least in the past, were increased to the point that further hunting of already weakened populations caused rapid decline in polar bear populations in many areas.

A new cycle has begun. From growing disruptions in the complex workings of the Arctic ecosystem, the whole food web and the land itself is being taxed. The changing state of the polynyas is but a symptom of a greater illness that is sweeping the North. Those creatures that cannot adapt fast enough to the rapid changes in sea ice and prey availability, face decline and possible extirpation, if not extinction. Unfortunately, polar bears, being an umbrella species, an environmental indicator, and being a large carnivore, will suffer greater peril. Polar bears rely on healthy polynyas to survive. If these areas disappear then so to may the polar bear.