December 6, 2012 | Vol. 39, No. 49

Calving on LeConte Glacier is amplified by submarine melting

Roman Motyka of the University of Alaska Fairbanks Geophysical Institute held a presentation on the effects of submarine melting on LeConte Glacier.

PIlot file photo

LeConte Glacier is located approximately 21 miles east of Petersburg and is the Northern Hemisphere's southernmost tidewater glacier and flows southwest to the head of LeConte Bay.

“Submarine melting can contribute to ice loss at the terminus of a temperate tidewater glacier, especially deep-water systems,” Motyka said. “In the case of LeConte Glacier in late summer, we have found that melting was at least as significant as calving.”

Motyka, along with Petersburg High School students monitored the calving events between mid May and September of this year with a camera set to take a photo every half hour for this time period.

“With the time lapse, we can really see just how fast the ice is moving,” Motyka stated. “We have determined that it is moving at around 27 meters per day.”

At the face, the glacier is about 240 meters deep which converts to 720 feet under the surface.

“Most of the glacier is under the water,” Motyka explained. “What we think is going on is that the saltwater is being brought in and melting out underneath which causes the calving and this usually happens in late summer.”

At this time, Motyka explained that 50 percent of the estimated total ice loss at the terminus is due to submarine melting.

“The calving terminus undergoes seasonal changes that coincide with changes in subglacial discharge and fjord water temperatures,” Motyka stated. “We believe that these fluctuations in terminus position are directly related to changes in submarine melting.”

Since the 1980s, it has retreated nearly 2.5 miles but is considered in a stable position today.

LeConte Glacier is also known for its shooter icebergs which calve off underneath the water and shoot out of the water due to their buoyancy.

“Huge streams of water are coming from beneath the glacier,” Motyka said. “This is happening 720 feet below the surface of the water and these pieces rocket to the surface.”

Motyka also stated that these glaciers are a spectacular sight if you are lucky enough to be there when they are calving.

LeConte Glacier is a popular tourist destination, with operators from Petersburg and Wrangell running excursions to the bay in the summer months.

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