Explore the historic cycle of advance and retreat of tidewater glaciers in southeast Alaska, in this video adapted from KTOO. Over the past 250 years, most glaciers in this region have lost more of their mass through melting and calving than they have gained through the new accumulation of snow and ice. This signals the end of a cooling trend called the Little Ice Age, which lasted nearly 3,000 years. If this period of retreat is extended by global warming, scientists warn that it may result in outright loss of the glaciers.