A growing glacier

WASHINGTON -- Whitney Glacier on Mount Shasta is growing, and scientists think global warming in Northern California is the reason.

This is not the way global warming works in most parts of the world.

In the Arctic and the Antarctic, and all along the West Coast north of the California border, temperatures are rising and glaciers are melting. Nisqually Glacier on Mount Rainier on the northern end of the Cascades, for example, has retreated by nearly a mile in the past century and continues to shrink.

But Whitney Glacier, on the southern end of the Cascades? "It's still growing," said Slawek Tulaczyk, a glaciologist at the University of California, Santa Cruz.

According to an article last summer in California Wild, a journal of the California Academy of Sciences, Whitney Glacier is the only ice river in the world that is larger today than in 1890.

Tulaczyk and his team, who began studying the glacier in 2002 and now have expanded their work to the high peaks of the Sierra Nevada, link the advancing frozen mass to the unique way California is being affected by global warming.

While in the short term it means more snow, their findings also contain a dire forecast: High-altitude snowpack, a steady source of water for the state as the snow melts during the summer, is probably doomed.

Tulaczyk said he and his team reviewed records dating back five decades collected from monitoring stations that measure the snowpack and its moisture content.

By comparing those statistics against temperature trends, certain conclusions can be drawn. A key conclusion is that global warming is not just about rising temperatures, but about the capacity of warmer air to carry moisture.

As California's temperature rose by 1 degree Celsius over the past half-century, Tulaczyk said, the snowpack has moved higher up in the mountains. But because warmer air in the winter can carry more water, the amount of snow falling at the high peaks has grown.

"At the higher elevations and on Mount Shasta there is more snow being dumped," he said. By their calculations, it takes a 20 percent increase in snow precipitation to counteract a 1-degree rise in the temperature.

So far, greater snowfall at the higher elevations has been able to balance out the loss of lower-elevation snowpack. But with models forecasting temperature increases of another 3 or 4 degrees, Tulaczyk said snow precipitation at the higher levels would have to double to maintain equilibrium.

That's not likely to happen, he said.

And that means that Whitney Glacier, as well as the snowy peaks of the Sierra Nevada, soon will begin to disappear before the summer months when their water is most needed.

In a paper published by Climate Dynamics, Tulaczyk and his team reach this grim conclusion: Greenhouse-driven temperature increases will "result in the loss of most of Mount Shasta's glacier volume over the next 50 years with near total loss by the end of the century."

In a separate paper, the research team says the same thing will happen in the Sierra Nevada.

"Glaciers exist only where snow can persist through all of the summer," Tulaczyk said. "So, disappearance of glaciers on Mount Shasta would mean also that there will be no summer snowpack on the mountain. The mountain will be more like most of the Sierra Nevada. It will have a winter snowpack that will completely melt in spring and summer."

This phenomenon may pose serious challenges to agencies that manage the state's water supply.

It also may be bad news for Nestlé USA, which is planning to build a 500-million-gallon-a-year bottling plant in McCloud, tapping springs fed by Mount Shasta. It has a 50-year contract that could be extended another 50 years.

"We have this wonderful water that is clean and plentiful," said Tonya Dowse of the Siskiyou County Economic Development Council, which sees the plant as a big boost to a community hard hit by the closure of its timber mill. The plant will market Mount Shasta water under Nestlé's Arrowhead brand.

Nestlé spokesman David Palais is not worried, either.

"There's plenty of water," he said.

But if the models Tulaczyk relies upon are correct, before the Nestlé contract winds down, Whitney Glacier and snow-capped Mount Shasta could be just a pile of rocks for half the year.

"This is quite worrisome," he said.

For now, however, the still-growing glacier can cause a different sort of problem.

In July, during a hot spell, the U.S. Forest Service issued a warning to motorists: Highway 97 was being flooded because of the volume of water melting from Whitney Glacier.

About the writer:

• The Bee's David Whitney can be reached at (202) 383-0004 or dwhitney@mcclatchydc.com.