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Peninsula glaciers give climate clues

Posted: Sunday, August 01, 2004

Along the Kenai Peninsula's spine lies an ice-age no-man's land few people ever see. Vast tracts of snow gleam year-round, punctured by jagged horns of rock, and blue rivers of ice tumble from the frozen highlands.

These icefields and glaciers are attracting increased attention from scientists.

Climate change could thaw them with drastic consequences. Global warming is controversial, and Kenai Peninsula studies are in the thick of the debate.

Kenai Peninsula's icefields and glaciers cover about 1,775 square miles, roughly the size of Delaware. Snows from the humid outer coast feed them; in turn they feed the Kenai and Kasilof rivers and estuaries of Kachemak Bay.

Nearly all U.S. glaciers are Alaskan, and about two-thirds of those rim the Gulf of Alaska.

"After time in Alaska, you look at the glaciers Outside as hardly glaciers at all," said Rod March, a hydrologist with the U.S. Geological Survey (USGS), who has studied glaciers for three decades.

The Harding Icefield, stretching from Seward to Kachemak Bay, is the largest icefield entirely within U.S. boundaries and roughly the size of Rhode Island. To its north lies the Sargent Icefield, which drains into Prince William Sound. The peninsula's outlying icefields are the Spencer-Blackstone Ice Complex to the north and, to the south, the Grewingk-Yalik Ice Complex.

"Most of the glaciers in Alaska have been retreating more or less continuously since a peak in the late 1800s," March said.

 

Exit Glacier, near Seward, has been retreating for about 200 years and may disappear during this century. Joel Cusick, a geographic information systems specialist with the National Park Service, compared modern pictures of the glacier, such as this image from the 1950s, with newer photos taken last year. He estimates the glacier is retreating an average of 43 feet per year.

Photo courtesy of Joel Cusick, National Park Service

Portage Glacier is no longer visible from its visitor center opened in 1986.

Along Exit Glacier Road near Seward, drivers pass a little sign labeled "1899," showing the glacier's reach at that time. In about 200 years, Exit has retreated about a mile and a quarter. A 2001 study by National Park Service mapping specialist Joel Cusick estimated that the glacier has pulled back with an average loss of 43 feet per year.

The best way to see peninsula glaciers is from the air. Their lower edges have pulled back, rendering topographic maps out of date. Their surfaces at lower elevations are sinking. Along the glaciers' sides, slopes that bookend them show lines of bare rock at the ice's old height.

"It almost looks like a bathtub ring," March said.

Monitoring a glacier's vital signs

Peninsula glaciers are low, exist in distinct maritime and inland weather systems and vary from the landlocked (such as Exit) to those which calve into the sea (such as McCarty in Kenai Fjords).

The USGS picked a peninsula glacier as one of three in the nation for long-term, detailed monitoring. Starting in 1965 during the International Hydrological Decade, its scientists focused on Wolverine Glacier, a wedge of ice tumbling out of the Spencer-Blackstone Ice Complex and draining east into Port Nellie Juan.

The other wired glaciers are Gulkana in the Alaska Range and South Cascade in Washington.

 

Exit Glacier, near Seward, has been retreating for about 200 years and may disappear during this century. Joel Cusick, a geographic information systems specialist with the National Park Service, compared modern pictures of the glacier, such as this image from 2003, with older photos dating back to 1950. He estimates the glacier is retreating an average of 43 feet per year.

Photo courtesy of Joel Cusick, National Park Service

In 1966, USGS put permanent monitoring stations on Wolverine. These catch snow inputs at three elevations, measure ice speed, gauge meltwater outflow and record weather.

"Even the simplest things, like measuring snowpack, are really time-consuming and challenging," March explain-ed.

Twice a year, in spring and fall, a team from his Fairbanks office treks to the glacier to measure snow at its yearly minimum and maximum. Their most recent visit was May 11 to 14.

Just getting there is a challenge. Helicopter flights are increasingly pricey. Or they can take a floatplane to Paradise Lake and pack heavy equipment the last couple miles across mountains. Glaciologists usually opt for chopper charters out of Anchorage or Moose Pass.

Wolverine's big drawback is wind. Equipment and tents blow away. The USGS built a rustic A-frame cabin next to the ice for scientists and had to bolt it to the bedrock.

"Just this winter at Wolverine, the winds have been 70 to 80 miles per hour," March said.

Usually scientists measure snow depth with stakes or by digging snow pits. At the glacier, stakes blow away or get sucked under the ice and drift. Snow pits work poorly when more snow lies underneath.

Glaciologists get inventive to deal with the white-on-white problem. At Wolverine, they have put sawdust and sheets of plywood on late-summer ice to detect the line the following season. Last fall they used a new trick: rolling out metal hardware cloth. But they still spend much of their spring visits checking bearings, digging test holes and running around with metal detectors to find markers, March said.

Markers move 60 to 100 feet downstream in a year. This past winter, about 16 feet of snow buried them, typical for Wolverine's collection basin. The record snowfall there was nearly 50 feet in 1977, he said.

Wolverine was shrinking when glaciologists began measurements. In 1976, it began growing. In 1989, the trend reversed, and it shrank faster than ever.

This pattern was seen throughout the region: warmer temperatures and changes scientists describe as "unusual" rippling through natural systems during the 1990s.

Since 2000, the rate of shrinking has slowed and, in 2003, the glacier was nearly, but not quite, stable.

Wolverine is the most volatile and only maritime glacier in the USGS group, with links to ocean cycles such as the Pacific Decadal Oscillation and weather events such as El Nino, March said.

Over four decades of monitoring, the glacier's average thickness has thinned cumulatively by more than 30 feet, he said.

"It is definitely still shrinking. It is still getting smaller, but not as fast as it was in the 1990s," he said. "I don't have much hope for it going up at this point. Basically summers are longer and hotter."

Modern technology probes glaciers' secrets

In 1994, a single-engine Piper airplane zigzagged low over Harding Icefield, then skimmed the length of its prominent glaciers. On board were two glaciologists from the University of Alaska Fairbanks. Using new laser altimetry and global positioning systems, they mapped the ice's surface contours with ease and accuracy unimaginable to earlier scientists.

Keith Echelmeyer, who developed the measuring technique and piloted the first overflights, is a professor at the university's Geophysical Institute.

Back at the university, Icelandic graduate student Gud-finna Adalgeirsdottir compared their readings with maps from the 1950s. She concluded that the icefield's surface sank about 70 feet during the interval.

Where the USGS project examines how individual glaciers thicken and thin, advance or retreat, the university project looks at the bigger picture of how widespread such changes are.

"We do 100 glaciers; they do two," Echelmeyer said.

In the past decade, UAF scientists have flown their equipment over glaciers around the world. They returned to the Kenai in 1996 and 2002.

The 1996 trip almost ended in disaster.

Echelmeyer and two graduate students landed on top of Harding Icefield in June to set up a GPS reference station.

"It started snowing," he recalled, "and it didn't quit for a long time."

A summer blizzard pinned them down. The wind was so strong that Echelmeyer had to crawl into the cockpit during the strongest gusts, rev up the engine and fly the plane into the ground to keep it down.

 

Ben Kennedy, a hydrologist with the U.S. Geological Survey, climbs into a snow pit to measure the annual snowfall on Wolverine Glacier. Snowfall in the glacier's upper basin is the source of its ice.

Photo by Rod March, USGS

Snow collapsed their tent. The threesome cut up notebooks to create a makeshift card deck to pass time. They eked by on dwindling emergency rations. A Coast Guard rescue plane buzzed overhead but couldn't reach them. They pondered walking out.

Echelmeyer knew leaving would doom his plane, and the trio feared they would be too weak from hunger to traverse the dangerous ice.

After five days, the storm broke and they escaped. In Seward they headed for a restaurant.

"We ate and ate," he said.

Results of the second and third visits suggested that melting rates for peninsula glaciers and others in Alaska were accelerating.

The new technology can monitor ice surfaces more accurately from now on. The UAF glaciologists plan to fly the Alaska Range this summer and the peninsula again in 2005 or 2006.

But the real world is not simple

Charles Raymond, one of the world's leading glaciologists, visited the University of Alaska and presented a seminar on glaciers and climate change in Fairbanks in February. Citing numerous studies, he explained why individual glaciers react differently to global warming.

Temperature interacts with precipitation to feed or destroy glaciers. As weather warms, coastal precipitation often increases, piling new snow onto highlands. This can overwhelm increased melting and fatten up a river of ice. So warming may feed glaciers, especially at high elevations. But continued warming would eventually turn snow to rain, making such expansion temporary.

Another complication is the storage capacity of large ice bodies. The bigger and colder the mass, the more slowly it reacts to changes. For most glaciers, the time involved is decades long, Raymond said.

Echelmeyer noted that although a glacier's length reacts to complicated, long-range factors, thickness is more temperature sensitive. Glacier thinning is one of the world's best barometers of climate change, he said.

Worldwide, a few glaciers are growing or surging. But the overwhelming majority is shrinking.

Fortunately most of the world's land ice lies in gargantuan sheets over Greenland and Antarctica, so huge and frigid that temperature increases during our lives have had scant effect. It could take centuries of rampant warming to destroy them.

 

Scientists Ted Moran and Dennis Trabant traverse the upper reaches of Wolverine Glacier. Their team from the USGS visits the glacier twice a year to maintain a weather station, measure how much snow and runoff change its size.

Photo by Rod March, USGS

Keeping them around is definitely in our interest. Raymond said scientists estimate that melting all the world's land ice would raise sea level more than 200 feet.

Close to home, that would submerge the peninsula's coastal communities, make the highlands south of Soldotna an island and move the Kenai River's mouth inland to Funny River and Mackey Lakes.

Sea level is rising, Raymond said. Current estimates peg the rate at about 2 millimeters per year, about an inch every 13 years.

Even small rises add up to erosion and flooding for coastal lowlands. A significant amount of that new sea water comes from Alaska's coastal glaciers.

In 2002, UAF scientists published an article estimating how much water shrinking glaciers pour into the sea. They surveyed 67 glaciers, including 15 on the peninsula. They found ice thinning fastest along the arc from Prince William Sound to the Kenai's tip.

"These recent losses are nearly double the estimated annual loss from the entire Greenland Ice Sheet during the same time period and are much higher than previously published loss estimates for Alaska glaciers," they wrote in their summary. "They form the largest glaciological contribution to sea level yet measured."

 

Scientists Ted Moran and Dennis Trabant traverse the upper reaches of Wolverine Glacier. Their team from the USGS visits the glacier twice a year to maintain a weather station, measure how much snow and runoff change its size.

Photo by Rod March, USGS

Peninsula glaciers all shrank except Aialik, which looked stable. The one retreating fastest was Northeastern, in the mountains of Kenai Fjords above Northwestern Lagoon. It thinned an average of about 6 feet per year.

Hot times ahead for glaciers?

Peninsula glaciers won't disappear in our lifetimes, glaciologists predicted. But we cannot take them for granted.

Ongoing Alaska Department of Fish and Game studies at Skilak Lake suggest rapid melting is bad for salmon fry.

Increased silt in rearing lakes correlates with decreased productivity, but maybe losing glaciers altogether would improve water quality, central peninsula Fish and Game biologist Mark Willette said via e-mail.

Runoff would definitely change if glaciers disappear. They moderate precipitation fluctuations. During droughts, when hot, dry weather increases melt, they offset the loss of rain, March said.

Echelmeyer said reputable scientists now take global warming as a given and few think it is natural.

"Frankly, it has got to be due to humans," he said. "My feeling is if we don't do something about pollutants, it will be too late."

March spoke more cautiously.

"Most of the big climate models seem to be predicting it will get warmer," he said.

He referred to "noisy" data and uncertainties about how much snow a warmer ocean would dump on the mountains.

"So I don't know. I wouldn't want to predict the future as far as climate goes," he said.

If current trends continue, how long will Kenai Peninsula glaciers survive?

"Certainly 100 years," Echelmeyer said. But then he added, "Exit Glacier may not continue that long."

The Harding Icefield is about 1,000 feet thick. But if ice bodies thin at the top, they sink to lower elevations with warmer temperatures. Feedback could accelerate melting, he said.

March, too, is guardedly pessimistic about the glaciers' future.

He forecast doom for those in the Lower 48. Within a generation, Glacier National Park in Montana will have no glaciers, he said.

Alaska's glaciers are bigger and colder.

"Is it something to worry about? The glaciers going away? Certainly not in the next 50 years," March said. "But certainly when you look hundreds of years down the road it's a valid concern. But up here it's a long ways away."



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