HARRIMAN GLACIER
Around the time I was staring at the Harriman Glacier’s dirty face, the Alaska Dispatch News published a six-page photo essay with the headline GLOBAL WARMING DOUBTER? COMPARE THESE IMAGES. In before-and-after shots spanning a century or more, some of Alaska’s most famous ice was shown to have melted away like unwanted belly fat in a Weight Watchers ad. One spread contrasted a 1905 picture of the robust Toboggan Glacier, just a few miles northeast of the Harriman, with a recent shot. The modern image showed a frozen puddle tucked into an otherwise green valley.
Bruce Molnia, the man who’d assembled the photo pairs, calls his image-comparison methodology “repeat precision photography.” Molnia is a research geologist at the U.S. Geological Survey, based in Reston, Virginia, and the author of a very thick book titled Glaciers of Alaska. He’s one of the few people who’ve spent more time flipping through the Harriman Alaska Series than I have. Glacial behavior is an excellent indicator of slight changes in climate. The thousands of photos Molnia had collected demonstrated overwhelmingly that Alaska’s glaciers have retreated in the past century. A few, like the Johns Hopkins in Glacier Bay and the Hubbard, near Yakutat, showed growth, though. What did it mean if glaciers were both advancing and retreating?
Not surprisingly for a geologist, Molnia takes a very long view of what he calls “the frozen part of the hydrosphere”: glaciers, sea ice, and permafrost. Glaciers are not eternal fixtures of the landscape; over the past two-plus billion years (“as long as the Earth has had an atmosphere”) they have come and gone on a continental scale hundreds of times, in cycles that have lasted millennia. Coastal cities such as New York, Miami, and Norfolk are bracing for a predicted sea level rise of up to three feet by 2100, which would inundate their lowest-lying coastal areas and cause hundreds of billions of dollars of infrastructure damage. Molnia reminded me that 125,000 years ago, sea levels were probably twenty feet higher than they are today. When global temperatures fell and the ice sheets advanced, these levels fell to more than four hundred feet lower than they are now, exposing the Bering Land Bridge. “I hear people say, ‘It’s never been this warm,’ or, ‘Sea levels have never risen this fast,’” Molnia said. “Let’s put this in perspective. Twenty-one thousand years ago, if there had been an Empire State Building and you stood on the top floor and looked east, you would not have been able to see the Atlantic Ocean, because the shoreline was sixty to seventy miles further away.”
I’d heard guesses as to how many of Alaska’s large valley glaciers are shrinking that ranged from half to 90 percent. The correct answer, Molnia said, is greater than 99 percent. The few that are growing—not even a dozen, depending on local conditions—aren’t evidence refuting climate change. Advancing glaciers such as the Hubbard and the Johns Hopkins have fluctuated over time as others have. The Hubbard is more than fifty miles long and draws from an extremely high source area (that is, its maximum elevation exceeds ten thousand feet above sea level) with heavy precipitation. Some of the ice that cruise ship passengers see calving off its front probably fell as snow before Columbus piloted the Santa Maria across the ocean.
The recent retreat of Alaska’s glaciers seems especially dramatic, Molnia said, because many expanded so significantly during the cooling period of the Little Ice Age. “Greenhouse gases are a major factor in causing the recent changes in earth temperatures and the extent of glaciers, but the Little Ice Age started less than a thousand years ago and ended in some places as early as 1750,” Molnia said. “In some cases, the volume of ice lost between 1750 and 1850 in places like Glacier Bay greatly exceeds that lost in the past hundred years in the same areas.” Today, most of Alaska’s valley glaciers would still be retreating without the effects of global warming, just more slowly.
Near the end of the nineteenth century, the Swedish chemist Svante Arrhenius attempted to uncover the cause of ice ages. He calculated that the level of carbon dioxide in the atmosphere had the effect of a thermostat; if CO2 levels declined, an ice age resulted. If levels rose, temperatures would rise, too. (As a resident of frosty Sweden, Arrhenius saw this potential warming as a positive development.) The vast majority of the world’s climate scientists now agree that global warming is primarily the result of increased concentrations of gases in the atmosphere, especially carbon dioxide, which is emitted during the burning of fossil fuels. Starting around 1850 with the late Industrial Revolution, atmospheric concentrations of CO2 have accelerated. Humans have been cranking up the earth’s thermostat ever since.
For some time now, Alaska has been warming twice as fast as the rest of the United States. The effects of this change are so obvious that even the state’s most anti-environmental politicians—a rather non-exclusive club—had to admit that something was going on. The same legislature that couldn’t agree on how to balance a budget without upsetting oil companies or reducing Permanent Fund dividend checks nevertheless established the Alaska Climate Change Impact Mitigation Program in 2008 to assist the state’s many communities dealing with erosion, flooding, and thawing permafrost. (As a sort of global-warming multiplier, thawing permafrost also releases huge amounts of CO2 and methane into the atmosphere when long-frozen organic matter decomposes. Methane has a more powerful effect on human-induced warming than CO2, but atmospheric concentrations of CO2 are much greater.) The growing season of interior Alaska expanded by 45 percent in the past century and is expected to continue lengthening. Plant and animal species have migrated north. The number and intensity of forest fires have increased. A patch of warm water nicknamed “the blob” has parked in the Gulf of Alaska, with devastating effects on the marine food web.
Faced with overwhelming evidence, the Alaska coalition in Washington, DC, has adopted the position that, while climate change is definitely occurring, no radical steps should be taken to fight it, because, to use a favorite phrase, “the science isn’t settled.” As George Bird Grinnell said about the overfishing of salmon, nothing is done and the bad work goes on.
The rising temperatures that launched the Holocene epoch, around 11,700 years ago, spurred the growth of agriculture, cities, civilization, and, eventually, the Industrial Revolution and coal-burning railroads that closed the American frontier. Nomadic tribes adapting to the end of the last ice age could migrate when sea levels rose too high. You can gas up your Escalade and escape a flood, but you can’t pick up and move the Empire State Building, or Bangladesh, or Shishmaref.
I e-mailed Molnia a photo I’d taken of the Harriman Glacier to get his prognosis. He said that, unlike its neighbor the Toboggan Glacier, the Harriman looked pretty healthy. What I’d thought was exposed bedrock turned out to be moraine—debris pushed forward by a moving glacier that can actually slow its melting by protecting it from seawater.
“People ask me all the time, ‘When are Alaska’s glaciers going to be gone?’” Molnia said. “The simple answer is, never”—for those at the highest and coldest elevations, anyway—“‘never’ being millions of years.” For tidewater glaciers like the Harriman, however, which have shrunk in number from about two hundred, at the end of the Little Ice Age, to fewer than fifty today, the trend line is definitely pointed in the wrong direction.
“I can’t imagine the Hubbard or the Johns Hopkins being gone in the next century,” Molnia said. However, warming temperatures cause ocean temperatures to increase, which accelerates the rate of melting and ice loss at lower elevations. “If you want to see glaciers that are easily accessible from the deck of a ship before they’re gone, you need to get moving.”