Southeast Greenland polar bears adapt to the loss of sea ice, for now

(CN) — Led by Kristin Laidre of the University of Washington and Greenland Institute of Natural Resources, a research team spent 36 years studying the Southeast Greenland polar bears. Particularly, how the polar bears hunt on the freshwater ice all year.

Published in the journal Science, the study reports that sea ice is vital to the polar bears' hunt. The animals use sea ice as platforms to jump from or to rest areas between their hunts of unaware seals. However, the study says that the Artic is warming more than twice as fast as the rest of the planet.

Laidre and her team researched the Southeast Greenland polar bears’ movements, genetic and demographic information, and traditional ecological knowledge. They reported that the polar bears used fresh ice at the marine terminal glacier fronts,  known as glacial mélange, to hunt the seals year-round.

According to the study, free floating sea ice intermittently flushes into fjords. However, they don’t provide enough support for polar bears because it has low concentration and last a short amount of time. Southeast Greenland bears use fast ice, sea ice frozen to the coastline.

“Elsewhere, bears depend on sea ice (not freshwater ice) to hunt seals,” wrote Elizabeth Peacock of Emory University School of Medicine via email. “In this area of southeast Greenland, there is not enough sea ice left for the bears to subsist. So, it is interesting that they are using this other option."

Also, the Southeast Greenland bears tend to stay in one place. Laidre and the team reported that they tracked all Southeast Greenland bears that moved out of the fjords. The current's drift ice cause these bears and drifted them southward an average of 189 km (117 miles). Without fail, every bear swam ashore and walked back to their home fjord within one to two months. The study is quick to point out that the bears cannot move from their fjords without risking contact with human-inhabited areas. Because of this and other factors, South Greenland polar bears are the most genetically isolated polar bears with one of the lowest birth rates.

Given their lack of mobility, their use of fast ice becomes helpful with hunting. However, fast ice is only available between February and late May.

That means that the region is sea ice-free for more than 250 days per year. Polar bears' seasonal fasting threshold is estimated between 100 to 180 days.

According to Laidre and the other researchers, “the findings have implications for polar bear conservation, suggesting that marine-terminating glaciers, although of limited availability, may serve as previously unrecognized climate refugia.”

While Peacock believes there is more to learn about the polar bears and their behavior, and that as the ice melts they may find new ways to hunt, there are limits.

“This plastic behavior can only stretch so much,” wrote Peacock. “Ultimately, bears need ice as a platform to hunt seals. If climate change continues, not only will the extent and quality of sea ice continue to shrink, so will this glacial mélange. Polar bears will run out of options to survive."

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