For decades, Argentina’s Upsala Glacier — one of the largest freshwater-calving glaciers in Patagonia — edged back slowly into the mountains. In the early 2000s the front was still relatively steady, but around 2008 something changed: the glacier began to pull away faster, its ice flowing quicker and its surface lowering significantly. From 2000 to 2011, the glacier’s terminus retreated roughly 3.5 km — about the length of 35 football fields — with most of that loss happening after 2008 as it en