Projected Models Show a Shaky Future for the Polar Bear

WHOI’s Ocean and Climate Change Institute (OCCI) is conducting research in the ocean’s role in climate change. The institute supports a wide range of activities including seeding basic research, supporting long-term goals, as well as supporting research with implications for federal policy. One of the programs currently under study at the institute is the research being conducted linking the loss of sea ice with declines in polar bear populations. Hal Caswell of Woods hole Oceanographic institute and Christine Hunter of the University of Alaska led a study that concluded that melting Arctic ice is a critical threat to the bears survival and reproductive rates. The bears use the ice as a platform to hunt seals, their main food source. The United States Coast Guard has collected information about polar bears mortality rates, birth cycles, and habits. In the summer as Arctic Ocean ice declines survival and breeding decline. The studies drew on models that projected Arctic climate changes, and forecasts of ice conditions. In the model studies 10,000 simulations were projected. Although each parameter in the model is an estimate and therefore is associated with a statistical uncertainty the conclusions about critical effects of sea ice changes and the decline of the population are robust. Population models suggested that 130 ice-free days is a threshold and considered a bad ice year. The frequency of bad ice years is the critical factor. If they occur more often than once every six years the bear population shrinks. Climate models have predicted that bad ice years will occur more often in the coming years due to warming in the Arctic. This scientist’s say means an uncertain future for the polar bear.