Excerpted below is Part III of three dispatches from a New York Times reporting trip to Antarctica.
From the air, the Ross Ice Shelf looks like a vast white plain extending to the horizon. The monochromatic landscape is relieved only occasionally by rocks poking through, or by deep crevasses in the ice itself.
Only at its edge does the ice shelf become something more dramatic: a spectacular sheer cliff rising 100 feet above the ocean and extending 900 feet below the surface. From that cliff edge, icebergs occasionally calve away, completing a thousand-year journey of the ice from land to sea.
Scientists are racing to understand what is happening to the Ross Ice Shelf — and the rest of Antarctica — as the planet warms around it. They are trying to map the thickness of the ice and the shape of the sea flood beneath it in an effort to gauge how vulnerable the shelf may be to collapse, and how soon that could happen.
Scientists are also trying to measure the role of human-caused climate change in weakening some parts of the West Antarctic ice sheet, and to fathom how damaging the seas around the continent might prove ot be as they warm over time.