Washington, Feb. 1 -- A gigantic cavity two-thirds the area of Manhattan and almost 1,000 feet (300 meters) tall growing at the bottom of Thwaites Glacier in West Antarctica is one of several disturbing discoveries reported in a new NASA-led study of the disintegrating glacier.

The findings highlight the need for detailed observations of Antarctic glaciers undersides in calculating how fast global sea levels will rise in response to climate change. Researchers expected to find some gaps between ice and bedrock at Thwaites bottom where ocean water could flow in and melt the glacier from below. The size and explosive growth rate of the newfound hole, however, surprised them. Its big enough to have contained 14 billion tons of ice, and most o...