Columbia Glacier (Alaska)
The Columbia Glacier is a glacier in Prince William Sound on the south coast of the U.S. state of Alaska, is one of the fastest moving glaciers in the world, and has been retreating since the early 1980s. It was named after Columbia University, one of several glaciers in the area named for elite U.S. colleges by the Harriman Alaska Expedition in 1899. The head of the main branch of the glacier originates at the saddle between Mount Witherspoon and Mount Einstein. The Alaska Marine Highway vessel M/V "Columbia" is named after the Columbia Glacier. Size . The glacier twists its way through western Alaska's Chugach Mountains. The bald streak at the bottom of the mountains, called the trimline, shows this glacier has lost of thickness. It has also retreated since that measurement was taken. Retreat. The glacier's speed of retreat at the terminus reached a maximum of nearly per day in 2001, when it was discharging icebergs at approximately r per year; the glacier has subsequently slowed down, resulting in an increase in retreat rate. The terminus has retreated a total of at an average rate of approximately per year since 1982. The retreat  has been accompanied by nearly of thinning at the present position of the terminus. In the next few decades it is expected to retreat another , to a point where the bed of the glacier rises above sea level. Columbia Glacier's retreat should be completed around 2020. Tidewater glacier advance and retreat is not directly forced by climate (adjacent tidewater glaciers may be simultaneously advancing and retreating), but rapid retreat appears to be triggered by climate-forced long-term thinning.