Motion and change define a glacier's life. Glaciers grow and shrink in response to changing climate. Typically, glacier movement occurs over long periods of time (hundreds to thousands of years), but within historic memory, such transformations in fewer than 100 years are not unknown.

Not all glaciers move slowly. For example, surging glaciers can flow quickly, sometimes traveling as much as ten to one hundred times faster than the normal rate of movement. Others may retreat within only a few decades, leaving once glaciated valleys blooming with vegetation again.

Over the spatial scale of kilometers, and over the temporal scale of centuries, glaciers can experience random changes in a constant climate, so glacier retreat by itself does not necessarily prove climate is warming. Glaciers have, however, provided corroborating evidence of climate warming across most of the globe. By monitoring glaciers over time and around the world, researchers construct valuable records of glacial activity and their response to climate variations.

By comparing contemporary observations with historical and environmental records, such as agricultural records, and prehistoric temperature or climate profiles, glaciologists acquire and provide an enhanced understanding of global processes and change.

Last updated: 16 March 2020