A second consecutive year of low sea ice in the Bering Sea has scientists examining whether it is tied to climate change. Much of the eastern Bering Sea is usually covered by thick ice in the winter. But unusual warm water and winds from the south have combined to keep ice levels around half of normal. It could be tied to changes in the jet stream associated with broader trends of rising temperatures and shrinking ice in the Arctic. If the changes persist, it could upend an ecosystem that supports one of the richest U.S. fisheries. Scientists are already seeing signs the loss of sea ice is affecting algae, zooplankton, and a range of other species that rely on these central parts of the food web.