The Dying Glaciers of California: The Snowcap Is Melting, Threatening the Alpine Ecology and the State's Water Supply
Miller, Jeremy, Earth Island Journal
IN August 1872, A 34-YEAR-OLD John Muir climbed the snow and ice of Mount Lyell and Mount Maclure into the highest reaches of what is today Yosemite National Park. The journey to the high country was no pleasure trip, but an expedition intended to resolve a bitter scientific dispute. The climb, chronicled in "The Living Glaciers of California," published in the November 1875 issue of Harper's Magazine, would hold great geological significance as Muir gathered evidence for the formation of the Sierra Nevada's distinctive granite valleys.
At the time, no one had collected any evidence to suggest that the permanent ice and snowfields in the Sierra's high basins were "living" glaciers. Muir believed they were. He posited that in a distant, colder past, these small glaciers once ran like great rivers of ice, carving the granite canyons of the western Sierra, including the majestic defile of Yosemite Valley itself.
Muir's most outspoken intellectual opponent was Josiah Whitney, an eminent geologist who derided the Scotsman as an "ignoramus" for straying into a field in which he possessed no formal training. Whitney had a competing hypothesis. He believed Yosemite Valley had been created during a cataclysmic earthquake in which the massive granite uplift had been shaken violently--like a rising cake jostled in the oven--forming a deep furrow through its midsection.
Muir was undeterred. On August 21, 1872, he ascended the snowfield on the northern shoulder of Mount Maclure, joined by Galen Clark (the first appointed "guardian" of Yosemite) and University of California professor Joseph LeConte. The group hauled bulky stakes hewn from whitebark pine and drove them five feet into the ice. The experiment was simple but elegant. Using a plumb bob rigged from a strand of horsehair and a stone, Muir surveyed the stakes, making sure they were in a straight line. Muir would return to the spot the first week of October. If the stakes had moved, he would have evidence that the patch of ice was not merely a permanent snowfield but a "living" glacier, pulled downhill by gravity and, in the process, gouging out the mountain below.
When Muir returned to Mount Maclure on October 6, 1872, he found that all his stakes had moved. One marker had traveled less than a foot, but several others slid nearly four feet. By his reckoning, the stakes that showed the greatest displacement had been moving downhill at a clip of one inch per twenty-four hours.
Muir's scientific feud would drag on for several years after his discovery on the Maclure. Nearly a century and a half later, the debate mostly has been settled. Geologists agree that the granite of Yosemite's famed cliffs was pushed up from great chambers of magma beneath Earth's surface and, over 50 million years, Yosemite Valley was simultaneously uplifted and cut by the Merced River. Then, around two to three million years ago, Earth's climate rapidly cooled. The small glaciers of the Sierra became massive ploughs of ice, 2,000 feet thick. Over the next 750,000 years the glaciers would become the great shaping forces of Yosemite.
Today, new forces are shaping the Sierra, California, and the entire planet. In the 140-plus years since Muir came down from the mountain, the Golden State has grown from 560,000 to 37 million people, and 4 million visitors arrive at Yosemite Valley annually, the vast majority of them in automobiles spewing C[O.sub.2]. Global carbon dioxide concentrations have jumped from 280 parts per million in 1850 to 400 parts per million today--warming the planet and, in the process, thawing the mountain snowfields.
These mid-latitude mountain glaciers, even more than their Arctic cousins, are powerful indicators of global climate change. They also signal serious regional consequences, namely decline in the snowpack, the lifeblood of the state's two heavily engineered river systems: the Sacramento and San Joaquin. …