| Summary: | Climate change is accelerating glacier melt. In the same month that this book first went to the editors, scientists reported the irreversible collapse of a massive portion of the West Antarctic ice sheet at Thwaites Glacier. Thwaites Glacier had already been news years earlier when a massive piece of ice 50 km (31 mi) wide, nearly 150 km (93 mi) long, and 3 km (1.8 mi) thick—that’s more than thirty city blocks of ice stacked on top of each other—broke off into the ocean and became Thwaites iceberg. Imagine an ice cube about seventy-five times the size of Manhattan Island floating away into the ocean. With the new reported collapse, the entire West Antarctic ice sheet has now entered into a rapid and irreversible melting phase (Figure 6.1). Thwaites Glacier, as well as others in the Amundsen Bay sector, such as the Pine Island Glacier, form part of a massive ice sheet on Antarctica that is falling to pieces. This is an ice sheet larger than France, Spain, Germany, and Italy combined, and it contains nearly 30 million cubic kilometers of ice (that’s about seven million cubic miles; Gosnell, 2005, p. 109). As these colossal ice bodies fall into the warmer ocean, they will begin to melt away, eventually raising global sea levels by about 1.2 meters (4 ft) (Figure 6.2). The breakdown has come much more quickly than expected and has now entered into an irreversible “runaway process.” What should have taken thousands of years in the natural evolution of things will now be complete in just centuries or less. The Pine Island Glacier is a long, flowing ice stream in the northeastern part of Amundsen Bay, and it is the world’s greatest contributor of ice to the oceans through melting and calving processes. It is also another of the glaciers at risk of collapsing entirely into the ocean. Thwaites Glacier’s collapse is an indicator that the whole ice sheet may be in imminent danger.
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