The creatures living in Antarctic oceans are accustomed to being cold. But even they barely survived the extra-frigid temperatures of the last ice age... At the peak of the last ice age, around 18,000 years ago, seals, birds and other polar animals would have had to eke out an existence around a few clearings — called polynyas — in the sea ice... The small openings would have served as year-round oases for algae to grow and form the basis of a food chain supporting fish, birds, seals and whales. At that time, the permanent sea ice that rings Antarctica would...