A stable glacier advances a little in the winter and retreats the same amount in the summer. Bear Glacier likely did this and gradually built up a terminal moraine. (A moraine is a buildup of glacial material, and a terminal moraine is one that is built up at the end of the glacier.)
During the last 100 years in Alaska, the annual average temperature has increased by about twice the global annual average temperature change. A temperature increase like this can change the regular pattern of glacial advance and retreat.
Between 1950 and the 1990s, Bear Glacier retreated 1.55 kilometers (1 mile). Small icebergs were calving into a lagoon that had developed. By 2004, the glacier’s floating terminus calved, causing an additional 2 kilometers (1.25 miles) of retreat. Between 2000 and 2007, the terminus retreated another 3.5 kilometers (2 miles). Large icebergs now float in the lagoon, visible in the Landsat images as light blue spots in the water.