Frequent climate fluctuations on the world’s southernmost continent have been so extreme over the past 5 million years that Antarctica’s Ross Ice Shelf, a floating slab of ice the size of France, oscillated in size dramatically, and perhaps even disappeared for periods of time when the West Antarctic Ice Sheet may have been smaller, according to scientists engaged in an unprecedented international geologic drilling project. Researchers with the Antarctic Geological Drilling (ANDRILL) Program, which concluded its first field season in January, say long cores of sedimentary rocks that they recovered from below the bed of the Ross Sea beneath the ice shelf allow them to peer deeply into the past to a time when Antarctica was a warmer, more inviting place. They were surprised, for example, to find such large volumes of fossil diatoms-microscopic single-celled algae that live in surface or shallow waters-in the cores. The presence of the fossilized one-cell creatures, some of them previously unknown to science, confirms that large areas of the Ross Ice Shelf have previously melted and were replaced with highly productive open waters. Studies of the cores may provide scientists with glimpses into the planet’s future if predictions of global temperature […]