Polar Bear picture by Kathy Crane, NOAA Arctic Research Program

A new study in November 2014 has found that polar bears in the Canadian Arctic Archipelago may be at risk of starvation and reproductive failure by the end of the 21st century.

Throughout the world, or at least the icy northern parts of it where polar bears actually live, the global population of polar bears is split into 19 separate sub-populations.  Seven of these subpopulations reside in the Canadian Arctic Archipelago, comprising about a quarter of the world's total polar bears and almost a tenth of the global polar bear habitat. 

It has previously been thought that the Canadian Arctic Archipelago and Greenland were the most likely places for Polar bears to survive global climate changes until the end of the 21st Century.  However, this latest study predicts that even in one of these possible last places of refuge, time could soon be up for this iconic creature.

Sea ice is vital for polar bears to hunt, migrate and mate.  What is known as multiyear ice is of particular importance. This is ice which last throughout more than one melting season.  

Unlike multiyear ice, a different type of ice is known as annual ice.  This is where ice completely melts to water during the warmer seasons.

The study, published by PLOS one, predicts that global warming will cause a shifting away from multiyear ice to annual ice in all areas of the Canadian Arctic Archipelago where polar bear populations are found.  This, in addition to increasing periods of completely ice-free conditions, could be critical for polar bears before the year 2100.  The remaining annual ice may not stay around long enough each year to allow adequate hunting opportunities for polar bears before melting away again.  Polar bears in the Canadian Arctic Archipelago may have to endure 2 to 5 months of ice-free conditions, something that does not exist currently.  

As well as the extended period of ice-free conditions, general ice thickness and snow depth are predicted to decline considerably, with ice thickness expected to be between a half and a fifth of that experienced in the late 20th century.

The Polar bear's main prey is the ringed seal which requires a minimum depth of around 20cm of snow for its habitat.  Average snow depth in South and Central Canadian Arctic Archipelago is predicted to reduce to less than half its current level by the late 21st century.  Only two areas, the Queen Elizabeth and Norwegian Bay, are expected to have enough snow depth for significant ringed seal populations to remain.

In addition, large areas are predicted to be completely ice free for 2 to 5 months a year, and not even reach 100% sea ice concentration even in the coldest months.  Polar bears usualy abandon the ice when the sea ice concentration drops to low levels.

When sea ice is in low concentration or absent, polar bears must swim to dry land.  They are great swimmers and can swim for days over hundreds of miles to reach ice floes or land.  However, once on land they can find themselves with a lack of their primary prey and can lose body weight due to a lack of hunting opportunities. They are well adapted to long periods without food, but during such fasting periods they lose body weight.  Some populations are already losing body weight with bad consequences for reproduction and survival.   

The Western coast of Greenland and much of Baffin Bay may become unviable places for Polar bears even before 2050.  Early break up of ice in the narrow central Canadian Arctic Archipelago channels could become critical around 2060 to 2070.   By 2070, over 80% of the Canadian Arctic Archipelago could experience ice breakup in July, forcing pregnant mothers to swim to land early, which could negatively affect their pregnancies and likelihood of giving birth to viable offspring.

By 2100 all areas of the Canadian Arctic Archipelago could cross a critical point-of-no-return, putting the continued survival of polar bears there in serious jeopardy.

Unless we do something soon to reduce global warming and climate change, things are looking black for these iconic and beautiful white bears.