Columbia Glacier starts from icefields at elevations over 9,000 feet (2743 m) near Mount Witherspoon in the Chugach Mountains and flows east and then generally south for 23 miles (37 km) to Columbia Bay on the north coast of Prince William Sound, about 62 miles (100 km) northeast of Whittier and 23 miles (37 km) west of Valdez, Alaska. Mount Witherspoon has a glaciated summit elevation of 12,012 feet (3,661 m) and is situated 4.33 miles (7 km) northwest of Mount Einstein, with the heads of Yale Glacier and Columbia Glacier in a saddle between the summits. Columbia Bay is a fjord about 3 miles (4.8 km) wide at the entrance and contains Heather Island and several inlets such as Heather Bay and Granite Cove. The water depth in outer Columbia Bay is 900 feet (274 m) deep, decreasing to 66 feet (20 m) at the terminal moraine, and then increasing to 1440 feet (439 m) near the glacier terminus. Adjacent mountains reach elevations from 2,500 to 5,000 feet (762-1524 m). One prominent mountain is named Great Nunatak and is situated near the current terminus of the Columbia Glacier. Nunatak is an Inuit word for the summit or ridge of a mountain that protrudes from an ice field or glacier. Great Nunatak was until recently completely surrounded by glacier ice, but its status as a nunatak is obsolete because the Columbia Glacier retreated and the water of Columbia Bay replaced the ice on the north and west aspects of the mountain. The glacier has historically been called Live, Root, and Fremantle Glacier, and in 1899 was formally named after Columbia University in New York by the Harriman Alaska Expedition.
In 1794, the Columbia Glacier was seen from the mouth of the bay and indicated on a map by Joseph Whidbey during Captain George Vancouver‘s expedition. Whidbey’s map suggests that the glacier ended a short distance north of Heather Island but does not distinguish the glacier from the land. In 1887, Captain Samuel Applegate on the schooner Nellie Juan was under contract to the U.S. Coast and Geodetic Survey and mapped the ice front in about the same position with respect to Heather Island. In 1898, the glacier was visited by Captain A.O. Johansen of the Alaska Commercial Company on the steamship Dora and a sounding of 50 fathoms (91 m) was made near the ice front. That same year, the U.S. Secretary of War Daniel S. Lamont ordered that three military expeditions be organized for exploring the interior of Alaska. The second of these expeditions was under the command of Captain William R. Abercrombie of the U.S. Army. Emil Mahlo and F.C. Schrader, of the U.S. Geological Survey, were attached to this expedition as topographer and geologist respectively. The resulting maps of the Columbia Glacier showed a small island, but like the others before, does not represent the location of the ice front. The only fact indicated by these maps is that the glacier was not strikingly different in the years of observation between 1794 and 1900. In 1899, the Harriman Expedition visited Columbia Bay and Dr. Grove K. Gilbert stayed there for several days studying the glacier, making a detailed map, and taking a number of photographs which have since proven of great value in subsequent studies. In 1905, a U.S. Geological Survey expedition including Dr. U.S. Grant visited Columbia Glacier, and photographs were taken from the sites of some of Gilbert’s photographs in 1899. Other photographs were taken from the same sites by Grant and Higgins in 1908 and 1909 when the glacier was studied and the ice front mapped again. A series of National Geographic Society expeditions were made in 1909, 1910, and 1911. Photographs were made from several of the stations occupied by Gilbert and Grant. These studies showed that for much of the 20th century the glacier terminus was stranded and stable on a moraine just north of Heather Island.
In the 1970s, several glaciologists such as Austin Post of the U.S. Geological Survey, correctly predicted that the glacier would start a rapid retreat once it melted off the moraine exposing the glacier face to relatively warm seawater. Post was one of the first to propose the tidewater glacier cycle, where water depth at the terminus of a tidewater glacier strongly affects the rate of iceberg calving. Glaciers that terminate on a morainal shoal are generally stable, but once a glacier retreats into water that deepens as the ice front recedes, the calving rate increases rapidly and results in drastic retreat of the terminus. In 1982, Columbia Glacier became one of the fastest moving glaciers in the world when the terminus started dramatically calving and has since retreated more than 12 miles (20 km) to the north. The glacier’s speed of retreat reached a maximum of nearly 98 feet (30 m) per day when it was discharging icebergs at a rate of approximately 1.7 cubic miles (7 cu km) per year. The retreat of the terminus stalled between 2000 and 2006 because Great Nunatak and Kadin Peak created a channel constriction that held the ice in place. The Columbia Glacier has also thinned substantially and rings of freshly exposed rock, known as trim lines, became especially prominent around Columbia Bay in 2000. The retreat has also changed the way the glacier flows. In 1986, there were three main ice branches, the West Branch, the Main Branch, and a smaller branch that flowed around the eastern side of Great Nunatak. As the Columbia Glacier lost mass and thinned, the flow in the small eastern branch stalled, reversed, and eventually began flowing to the west of Great Nunatak. By 2011, the retreating terminus essentially split the Columbia into two separate glaciers, with calving occurring on two distinct fronts. In 2019, satellite imagery showed that the West Branch could be at the limit of its retreat. In 2014, the Main Branch had thinned so much that it no longer had contact against the channel bottom, and could be affected by tidal motion as far as 7.5 miles (12 km) upstream and once again unstable. In 2019, the Main Branch resumed retreat and started calving icebergs during an anomalously warm summer. The retreat of the Columbia Glacier contributes to global sea-level rise, mostly through iceberg calving, and this one glacier accounts for nearly half of the ice loss in the Chugach Mountains. Read more here and here. Explore more of the Columbia Glacier here: