 There are thousands of glaciers in Alaska but only few have been named . The Columbia Glacier near Valdez in Prince William Sound has retreated 15 km ( 9 @.@ 3 mi ) in the last 25 years . Its calved icebergs partially caused the Exxon Valdez oil spill , when the tanker changed course to avoid the ice tips . The Valdez Glacier is in the same area , and though it does not calve , has also retreated significantly . " A 2005 aerial survey of Alaskan coastal glaciers identified more than a dozen glaciers , many former tidewater and calving glaciers , including Grand Plateau , Alsek , Bear , and Excelsior Glaciers that are rapidly retreating . Of 2 @,@ 000 glaciers observed , 99 % are retreating . " Icy Bay in Alaska is fed by three large glaciers — Guyot , Yahtse , and Tyndall Glaciers — all of which have experienced a loss in length and thickness and , consequently , a loss in area . Tyndall Glacier became separated from the retreating Guyot Glacier in the 1960s and has retreated 24 km ( 15 mi ) since , averaging more than 500 m ( 1 @,@ 600 ft ) per year . 
