Polar Bears, Sea Ice, and Climate Change
Page 3 of 4
Click the image to enlarge.
Ice Conditions and Polar Bear Distribution
This project is the first to do comprehensive sea-ice modeling and attempt to relate that data to the movements of bears. By doing so, researchers are hoping to be able to explain some of the different patterns they've seen in polar bear movement and distribution over the years. As Amstrup explains, "We know that bears respond to temporal changes in the sea ice, and many of those changes are in response to changes in the ice that we haven't yet been able to figure out. In other words, it's not obvious to us how the ice is different; but it's obviously different to the bears."
The team is especially interested in how sea ice changes might be affecting how polar bears den in Alaska, where approximately half of the pregnant bears den on the sea ice every year — rather than on land, as they primarily do in other regions. The importance of looking at that question, according to Durner, is the possible effect on the overall polar bear population in the area. "When you have 50 percent of the pregnant population denning on the sea ice each year, that's a significant component of the population — and if they're greatly affected by changes in sea ice, that's going to have some effects on the population as a whole."
By analyzing the ice data for the Beaufort Sea and looking at elements such as total ice-cover concentration, proportion of multiyear versus first-year ice, and ocean depth, scientists plan to create a map of discrete sea-ice habitats. Then, through complex mathematical modeling, they can calculate the relative probability that polar bears will be found in each of those distinct sea-ice habitats. Combining their statistical model with actual polar bear location data collected since 1985 will help them zero-in on the particular ice characteristics preferred by polar bears. That's important in this climate-change discussion, according to Amstrup. "If we can see how changes in the sea ice relate to polar bear movement and distribution, then we should be able to predict how future changes are likely to influence bears. We know that the complete disappearance of sea ice would mean the end of polar bears, so we're looking at patterns short of the disappearance of sea ice — such as late freeze-up, less multiyear ice, and so on."
This project is the first to do comprehensive sea-ice modeling and attempt to relate that data to the movements of bears. By doing so, researchers are hoping to be able to explain some of the different patterns they've seen in polar bear movement and distribution over the years. As Amstrup explains, "We know that bears respond to temporal changes in the sea ice, and many of those changes are in response to changes in the ice that we haven't yet been able to figure out. In other words, it's not obvious to us how the ice is different; but it's obviously different to the bears."
The team is especially interested in how sea ice changes might be affecting how polar bears den in Alaska, where approximately half of the pregnant bears den on the sea ice every year — rather than on land, as they primarily do in other regions. The importance of looking at that question, according to Durner, is the possible effect on the overall polar bear population in the area. "When you have 50 percent of the pregnant population denning on the sea ice each year, that's a significant component of the population — and if they're greatly affected by changes in sea ice, that's going to have some effects on the population as a whole."
By analyzing the ice data for the Beaufort Sea and looking at elements such as total ice-cover concentration, proportion of multiyear versus first-year ice, and ocean depth, scientists plan to create a map of discrete sea-ice habitats. Then, through complex mathematical modeling, they can calculate the relative probability that polar bears will be found in each of those distinct sea-ice habitats. Combining their statistical model with actual polar bear location data collected since 1985 will help them zero-in on the particular ice characteristics preferred by polar bears. That's important in this climate-change discussion, according to Amstrup. "If we can see how changes in the sea ice relate to polar bear movement and distribution, then we should be able to predict how future changes are likely to influence bears. We know that the complete disappearance of sea ice would mean the end of polar bears, so we're looking at patterns short of the disappearance of sea ice — such as late freeze-up, less multiyear ice, and so on."