So there is a transient phenomenon where in some of these high Arctic areas, as it’s getting warmer and sea ice is melting, the conditions are getting to be just right. The multi-year sea ice can be 10 metres thick, so it stifles productivity. “Historically, there was actually too much sea ice in the high Arctic for bears. Dr Eric Regehr – a polar bear expert at the University of Washington – tells Carbon Brief why thinning ice could, temporarily, help some polar bears: However, in regions such as the Kane Basin, which is part of the “archipelago” group, a shift from thick, multi-year ice to thinner, seasonal ice has proved beneficial for bears. Video showing the migration pattern of polar bears from the Western Hudson Bay. For example, the video below shows how polar bears from the Western Hudson Bay migrate throughout the year in response to the annual cycle of growing and shrinking Arctic sea ice. In subregions including the Southern Beaufort Sea, Baffin Bay and Western Hudson Bay, sea-ice loss has been directly linked to past or present declines in the polar bear population. The differing behaviour of sea ice across the Arctic means that not all polar bear populations will respond in the same way to thinning ice. Year that ice area was above the midpoint calculated (i.e. ![]() Ice areas was determined, and the number of days per The midpoint between summer-minimum and winter-maximum Ice concentration and grid cell area over all 25x25 km grid Within each of the 19 subpopulation areas,ĭaily sea-ice area was calculated by summing the product of Analysis was not conducted for the 19th subpopulation – the Arctic Basin – due to the small polar bear subpopulation. It shows that ice decline is more notable in some regions than others. The paper plots sea-ice concentration in 18 of the 19 key regions over 1979-2014. This region is “likely to provide a last refuge for polar bears and their prey”.Ī review published in 2016 finds that “loss of Arctic sea ice owing to climate change is the primary threat to polar bears throughout their range”. Archipelago: Full ice coverage all year round.Convergent: In this region, ice collects along the shore in summer, allowing the bears to remain on sea ice all-year round.However, as the climate warms, the sea ice is retreating farther from shore. Divergent: This region has historically had ice coverage all year round.But in summer, the ice melts completely – so polar bears are forced ashore and largely live off their fat reserves until ice reforms. Seasonal: The “rich environment” allows bears to gain weight in spring.The latest Polar Bear Specialist Group status report ( pdf) outlines the patterns of ice coverage for each one: The four ecoregions are categorised by different seasonal ice melt and growth patterns. The Arctic Basin (AB) subpopulation likely has few year-round resident polar bears and is generally excluded from analyses. The chart below shows how Arctic sea ice extent has diminished in recent decades.Įcoregions provided by Eric Regehr. However, temperatures in the Arctic are rising nearly four times as fast as the global average, and Arctic sea ice extent has declined since 1979 for every month of the year. As such, sea ice is crucial for polar bears to survive. While polar bears are strong swimmers, capable of swimming for hours on end, they find swimming much more energy intensive than walking. Polar bears depend on sea ice for most important aspects of their lives – including hunting, mating and resting. While polar bears have shown some ability to adapt to changes in their surroundings – for example, by foraging for food on land, or swimming more to hunt for prey – scientists project that as sea ice diminishes, polar bears will find it harder to survive and populations will decline. The consensus is clear – as Arctic sea ice melts, polar bears are finding it harder to hunt, mate and breed. Yet every now and again, claims emerge in the media that polar bears’ plight might not be so serious after all.Ĭarbon Brief has dug through the literature on polar bears and climate change and spoken to experts from around the world to determine what a changing climate means for polar bears. The image of a polar bear stranded on melting sea ice is often used as a symbol of the world’s rapidly changing climate. ![]() 8 December 2022 Credit: Carbon Brief / Alamy Stock Photo.
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