Baked Alaska

In the late 1800s, Alaska’s top tourist attraction was Muir Glacier. Ladies in ankle-length dresses and gentlemen in neckties and fedora hats strolled a boardwalk at the foot of this natural wonder. Glaciers are still a big draw in Alaska; every year, more than 350,000 people visit Muir Glacier’s home, Glacier Bay National Park. But the scenery there has changed as dramatically as clothing fashions.

As mighty as glaciers look from the deck of a cruise ship, they are surprisingly fragile. A unique collection of photographs of Alaskan glaciers taken over the past century shows that as temperatures have risen there by about 5 degrees Fahrenheit, almost all of the glaciers have retreated into the hills. Bruce Molnia, a geologist with the U.S. Geological Survey (USGS) in Reston, Virginia, started collecting old photographs of Alaskan glaciers in the 1970s. He’s up to a few thousand so far, gathered from the USGS library in Denver, the National Snow and Ice Data Center at the University of Colorado in Boulder, the Alaska State Library and other archives, as well as picture postcards that people sent him or that he bought on eBay. The oldest pictures were taken in 1883 by a U.S. military expedition to the Yukon River. Molnia has updated 200 of the pictures, traveling to the very spots where each was taken and photographing the same scene at the same time of year. His pictures may be less precise than satellite analyses, GPS studies and other high-tech methods with which scientists track glaciers. But his before-and-after photographs offer perhaps the most vivid evidence that Alaska’s glaciers are indeed melting.

Often Molnia knew exactly where to pull out his camera. Some of the geologists who went before him kept careful records, and a few even built rock piles, or cairns, to mark for posterity where they took their photographs. “Sometimes, when I’m stumbling around in the brush trying to find the right spot, I’ll see a cairn built in 1909,” says Molnia. Some of the cairns are covered in shrubs and trees. New plant growth on slopes that were once bare bedrock is another sign that Alaska has warmed up in the past century. “Even if the older photos were in color, they would still be mostly black and white,” Molnia says; the new photographs show a lot of green. Geologists studying other historic images have found that lichens and mosses that thrive in high latitudes, and feed caribou, are losing ground to warmer-weather species.

Molnia’s double takes chronicle glaciers in Glacier Bay, Denali and Kenai Fjords National Parks and in the Chugach National Forest. Those places may seem plenty cold to a Lower-48’er, but the temperature does rise above freezing for several months each year, and the 5 degree increase in average annual temperature over the past 75 to 100 years has taken its toll. Of the glaciers that Molnia has studied, only 1 to 2 percent have grown, probably due to increased snowfall at higher elevations. The rest are visibly shrinking, one by 20 miles in 95 years. Such melting of glaciers and sea ice threatens 86 percent of Alaska’s villages with flooding and erosion, according to a 2003 study by the Government Accountability Office.

Glaciers are dwindling almost everywhere. In the Arctic National Wildlife Refuge, all the glaciers are shrinking. In Antarctica, and atop mountains in China, Peru and Argentina, glaciers are melting fast, as is the icy cap of Mount Kilimanjaro. If the current trend continues, says glaciologist Lonnie Thompson of Ohio State University, in 30 years Glacier National Park on the Montana-Canada border will have no glaciers.

Some glaciers started melting hundreds of years ago. The demise of Muir Glacier may have been hastened by a shattering earthquake in 1899. Natural variations in the earth’s climate, caused by volcanoes or wiggles in the earth’s orbit and orientation around the sun, which alter the amount of sunlight hitting the continents, have caused ice ages to come and go. But lately, especially in the past 50 years, almost all experts agree, a spike in carbon dioxide levels in the atmosphere has exaggerated the greenhouse effect, in which a buildup of certain gases traps heat. What’s more, because carbon dioxide lingers in the atmosphere, and because people are burning more carbon-dioxide-releasing fuel all the time, “the change in the next 150 years will dwarf the change in the past 150 years,” says David Battisti of the University of Washington. Computer simulations of future climate changes, which have been validated by testing them against historic climate changes, make the same prediction. “It’s going to be a very different world, a much warmer world,” says Michael Oppenheimer of Princeton University.

Glaciers are fed by snow; the weight of new snowfall squeezes old flakes into ice crystals that can grow as large as your head. When light pierces the compacted ice, red wavelengths are absorbed, leaving a ghostly blue glow. Forget about sapphires, cornflowers or even the sky—nature’s finest blue is glacier blue. Only once-deep glacier ice emits the cold color. You can see this bluest blue best at the bottom of a crevasse, or where glaciers are calving, or—more achingly beautiful still—where they are melting.

Laura Helmuth | | READ MORE

Laura Helmuth is the science and health editor at Slate. Previously, she was a senior science editor at Smithsonian magazine.