Sea ice is a requirement for polar bears to hunt seals. However, a small group of polar bears on the rugged coast of southeast Greenland has figured out how they can make a living off of the sea ice, which melts early in the year.
The freshwater ice from land glaciers has allowed these bears to replenish their sea ice supplies. According to Science, the glacial ice is blown into fjords in large chunks. The pieces then clump together to form a floating platform that the Polar Bears use to hunt seals.
Sea ice is becoming more scarce due to climate change. Kristin Laidre, a University of Washington researcher and the study's lead author, says that sea ice loss is "the main threat to polar bears." She says that this research suggests that bears may be able cope with reduced sea ice for a period of time aEUR," at least in areas where they have access to floating glacier ice like Greenland or Svalbard in the Arctic Ocean.
She says that "Glacial Ice basically might help small quantities of bears survive longer periods under climate change."
Although people in the region have known for a long time that bears live in southeast Greenland since ancient times, this remote and challenging area is not accessible to humans. Laidre says, "It's an coastline with huge mountain peak, lots of winds and extreme conditions, lots foggy," after spending years with colleagues to study polar bears along Greenland's 1,800-mile long east coast.
The team took helicopters from their nearest settlement to fly two hours straight to the coast in order to see what they could find. "We arrived at these fjords. They are very isolated fjords and there is essentially no sea-ice or very poor shore ice off the coast," Laidre says, explaining that they expected to find very few bears.
She says, "But there were many bears in these Fjords." It was clear that it was a special habitat.
She notes that the sea ice lasted in these fjords only for around 100 days per year. This means bears don’t have much time use it as a hunting area. Laidre says that the sea ice disappears in May and that is really early. "It takes too much time for a Polar Bear to become fat enough and live."
She says that the area's geography makes it possible for glaciers to pour freshwater into the fjords and over the mountains. The icebergs are formed from glaciers and can be used by polar bears to hunt seals. Laidre says that freshwater ice is used by the polar bears to supplement their hunting time.
The researchers would capture bears briefly when it was safe to land the helicopter. Laidre says, "We would gather information about their movements, their bodies condition, and their genetics."
She estimates that there are at least a few hundred polar bears living in southeast Greenland. It turns out they're one of the most genetically isolated species of polar bears anywhere on the planet. They are distinct from the 19 subpopulations of polar bears scientists have identified in the Arctic.
This could be because these bears are homebodies. The tracked bears stayed in their home fjords or fjords for the most part. Laidre says that the bears were occasionally caught in a strong sea current, which rips the coast towards the southern tip of Greenland. However, they would swim quickly to shore. "And then they would walk back over the ice to their fjord."
Todd Atwood, a U.S. Geological Survey Alaska Science Center Anchorage polar bear researcher, said that "the discovery of a possible new subpopulation is really interesting." According to Atwood, the bears' behavior, genetics and patterns of movement "make a compelling case" for this subpopulation.
Atwood says that the way these bears hunt with freshwater ice might "buy bears in that region a little more time, as pack-ice continues to decline because they aren't solely dependent on it."
Atwood says that polar bears are dependent on the sea freezing for long periods of time each year. He also said that research has shown that polar bear populations suffer steep declines if there is more than 180 days without ice. This is because the bears don't have enough seals to reproduce and survive.
The bears have a simple job to do. Ian Stirling, University of Alberta polar bear biologist, says that they have to stay on the ice long enough to kill enough seals and store enough fat for one year.
Stirling says that the rare areas in which polar bears can access glacier ice like southeast Greenland won't be a refuge from climate change for ever.
Stirling says that if the climate continues to heat as it's predicted to, these areas will also become of no or not enough use for the bears. Stirling notes that eventually, the glaciers' ends will melt away, allowing them to retreat to the ground rather than to the sea. He says that by the time that happens, there will be so much ice that the bears "will be long gone."