关键词: 北极熊, 开阔水域, 栖息地, 稳定性, 北极

Abstract:

Polar bear is one of the most important mammals in the Arctic, but its number decreased in recent years. Polar bears are sensitive to changes of the sea ice distribution and depend on sea ice as a platform for hunting, moving and reproducing. In other words, sea ice is an important part of polar bear habitat. Climate is the main factor of sea ice changes. Therefore, it is very important to understand the current situation of polar bears as well as the effect of climate on the Arctic ecosystem. Although many researchers have devoted to find polar bears habitat using aerial survey in recent years, their methods require considerable human involvement and cannot be used to detect all habitats rapidly and effectively. Thus, it is necessary to find a method to quickly assess the polar bear habitat changes. Based on the sea ice concentration products from the United States National Snow and Ice Data Center (NSIDC) and the ETOPO1 bedrock product provided by the NOAA, the inter-annual variability of sea ice concentration, open water area, sea ice retreat, sea ice advance and the length of the open water season in the Arctic were analyzed. Then, the polar bear habitat stability were analized. The results indicate that from 1989 to 2016 the sea ice concentration has decreased, open water area increased and multiyear ice decreased. Most of the multiyear ice has converted to one-year ice. The sea ice appeared later and retreated earlier, so the length of the open water season increased significantly, an increase of 72 days compared to 1992. Barents Sea is the region with the most significant changes in open water area and the length of open water season among 19 habitats, with increasing rates of 9.71×10³ km²/a and 71.69 days/decade, respectively. Based on the change rates of the length of the open water season, we divide the polar bears habitats into three levels of conditions: stable, sub-stable and instable. The three stable habitats, including the Chukchi sea, Western Hudson Bay and Southern Hudson Bay are located in the lower latitudes compared with other habitats. There are 13 sub-stable habitats, including Laptev Sea, Kara Sea, East Greenland, Baffin Bay, Davis Strait, Foxe Basin, Gulf of Boothia, M’Clintock Channel, Viscount Melville, Norwegian Bay, Northern Beaufort Southern Beaufort and Lancaster Sound. The three unstable habitats are located in the north of 70°N, including Arctic Basin, Barents Sea and Kane Basin. Stable habitats are mainly in low latitudes, and unstable regions are all in high latitudes. The classification results show that the high latitude area is covered with more sea ice, but the inter-annual variation is very significant. In three unstable regions, polar bears have less time to adapt to the sea ice changes, and the inter-annual migration changes greatly, which is less favorable to the survival and development of polar bears.

Key words: Polar bear, open water, habitat, stability, Arctic