That Dam Glacier

There are a few once-in-a-lifetime natural events some of us are lucky to witness—like the sighting of the Hale-Bopp comet, or the longest solar eclipse of the century. Most awe-inspiring natural events, though, occur in remote obscurity, remaining unknown to all but the few people who study them and usually discover them after the fact.

And then there’s southeastern Alaska’s Hubbard Glacier, the fastest-moving, largest tidewater glacier in North America. The glacier is on the verge of damming adjacent Russell Fjord at Gilbert Point. When the glacier seals the entrance it will create a 64-kilometer lake, a natural event that has rarely been observed as it happens.

The rapidly advancing Hubbard Glacier. Source: U.S. Forest Service

The rapidly advancing Hubbard Glacier. Source: U.S. Forest Service

Daniel Lawson of the Cold Regions Research and Engineering Laboratory will be there to document it thanks to a recent National Science Foundation grant.  He and several field researchers will visit the glacier to collect a variety of information about the lead up, the damming event itself, and its aftermath. They will use remote sensing information and a suite of sensors placed on the glacier surface to gather their data. The team will also visit observation points via helicopter or boat and will take several fixed-wing over-flights for aerial photography.

It's easy to see why the glacier is a cruise-ship favorite. Photo: Richard Wainscoat, http://www.wainscoat.com

It's easy to see why the glacier is a cruise-ship favorite. Photo: Richard Wainscoat, http://www.wainscoat.com

Completely closing Russell Fjord could devastate the salmon fisheries in the adjacent Situk River, an economic lifeblood for the city of Yakutat. According to a 2007 Forest Service report, closing the Hubbard-Russell ice dam will increase the river’s daily flows from 3 to 11 cubic meters per second (cms) to more than 566 cms if the lake flows over the glacial moraine. In addition to its prolific salmon fishery, the river draws myriad tourists to the region each year.

Located near Yakutat, the Hubbard Glacier encompasses an area of ~3900 square km, flowing 120 kilometers from the flanks of Mt. Logan (5959 meters and located in the Wrangell – St. Elias Mountains) to sea level, where its terminus widens to over 13 kilometers across the head of Disenchantment Bay and the entrance to Russell Fjord.

hubbard_glacier_map_locaterUnlike most southeastern Alaskan glaciers, Hubbard is thickening and advancing, most recently at an average rate of 35 meters per year for the last 15-16 years. The high accumulation area ratio (0.95) of Hubbard Glacier suggests that it will continue to advance for a hundred years or more, barring any significant changes in climate raising its Equilibrium Line Altitude (ELA) by nearly 1000 meters.

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