Tracking glaciers the Tangborn way
Wendell Tangborn thinks he has invented a better mousetrap. He's still waiting for the scientific world to beat a path to his door.
Sitting in a cramped home office overlooking the (rising) waters of Puget Sound, Tangborn talks about his plan to monitor 200 glaciers around the world to see whether or not — and, if so, how quickly — they're melting away. He has already done detailed reports on seven, including Juneau's incredible shrinking Mendenhall Glacier. He's working on 40 more, and hoping one or more foundations will supply enough money to hire the three people he'd need to keep track of all 200.
People often cite the waxing or waning of glaciers to prove that the earth is or is not getting warmer. But according to Tangborn, no one is looking systematically at a large number of glaciers so that trends become obvious and the glaciers which are behaving contrary to the trends can be seen clearly as outliers.
Basically, he uses temperature and precipitation data from fixed weather stations to calculate a glacier's "mass balance" — that is, the difference between the winter accumulation of snow and the summer melting of snow and ice. A positive balance means the glacier is growing; negative means it's shrinking.
The program must be customized for every glacier. Tangborn must take account of the topography and total area of the glacier's surface. Once he plugs that into the program, he can sit in his office and get information that's as reliable as the data produced the old-fashioned way — the way he did it for many years — by climbing around on the ice with probing rods and shovels.
For each glacier, Tangborn has to find a weather station that produces results in line with actual observations. That isn't necessarily the weather station right next door to the ice. Austrian scientists can't believe that Tangborn's using a weather station in Innsbruck to monitor the Vernagtferner glacier, which is 100 kilometers away, rather than a station close to the site. But, says Tangborn, somehow local weather phenomena keep the closer station from producing useful numbers.
Tangborn's monitoring program runs on old PCs in that office of his on the west side of Vashon Island. Big photographs of Alaska's Columbia Glacier adorn one wall. Tangborn studied that glacier in the 1990s with the late Austin Post. (Icebergs calved from the Columbia Glacier forced the tanker Exxon Valdez out of the normal sea lanes that night in 1989 when it ran aground and spilled 11 million gallons of crude oil into Prince William Sound.) The litter of publications includes a children's book on glaciers written by Tangborn himself.
Tangborn saw his first glacier in 1960, when the U.S. Geological Survey transferred him from his native Midwest to Washington and sent him out to the North Cascades to help study the South Glacier. That's the glacier just outside North Cascades National Park, whose meltwater feeds the south fork of the Cascade River. (The work was done for the Water Resources Division of the US Geological Survey, which had started it three years earlier, in part, to gauge the effects of climate change. The division's chief hydrologist at the time was Luna Leopold.)
Six years ago, Tangborn wrote about his first-year experience at the glacier for The Wild Cascades, published by the North Cascades Conservation Council. "It was a typical day at South Cascade Glacier in October," he wrote, "wet, cold, windy, cloudy and dark. After breakfast we gathered up the equipment we would need for the day (ice axes, current meter, measuring tapes, snow probing rods, rubber hip boots, collapsible wading rod), packed a lunch (a can of sardines, a box of Ry-Krisp and a can of apple sauce), dressed in the most water-proof clothes we could find and headed up glacier. The rain turned to snow as we gained elevation ... One of the vital goals of the project was to measure the glacier’s balance and determine if it was gaining or losing mass. Visibility was now down to 10 or 15 feet ... One measurement was a little frightening as it was just above [a round shaft], into which the glacier stream poured, making a thunderous roar as the water fell 200 feet to the glacier bed."
South Glacier is still "probably my favorite [glacier], because it was my first," says Tangborn. But South Glacier has become a shadow of its former self. Tangborn pulls up a series of aerial photographs, dating back to 1928. From 1928 to 1959, the glacier had pulled back a little. By 1979, it had pulled back a little more. By 2003, it had shrunk to less than half its 1928 length. (All of the monitored glaciers in nearby North Cascades National Park have lost volume since 1993.) South Glacier may be well down the road to oblivion.
After Tangborn left the U.S.G.S., he made a living forecasting snowpack and runoff in the Columbia Basin for electric utilities. He has modified his forecasting program into the one he now uses to track glaciers.
It's hard for traditional on-the-ground glaciologists to accept the idea that his way works just as well as theirs, because "it's too easy," says Tangborn. And it's not as much fun. Tangborn mentions an old colleague who thinks he should just drop the whole weather station approach. "He'll never accept it," Tangborn says.
He pulls up a graph on his computer screen. One line tracks the mass balance of a glacier as measured by people on the ice. The other tracks the same glacier's mass balance using his own program. The lines don't coincide, but the patterns match closely. Any way you look at it, the balance is negative; in other words, that glacier is shrinking.
Tangborn points out that the numbers are close enough to show the same trend — and that, besides, actual on-the-ice measurement isn't entirely accurate either. Satellite monitoring could track all of the earth's 160,000 glaciers, but it would be less precise, and besides, no one has made a satellite available for the job. For the time being, he says, this is as good as it's likely to get.
One can argue that, however you collect the data, there's not much point in knowing how fast the train is coming unless you're willing to get off the track. But that's another story.