John Muir first discovered what was to be known as the Lyell Glacier in 1871, hanging off Mount Lyell, the tallest peak in Yosemite. Some 150 years later, the Lyell Glacier is all but gone, killed by climate change, and its epitaph remains a brutal warning sign as to where life on Earth is headed.
On a cool September morning in 2014, among lodgepole pines under blue mountain sky, Greg Stock shouldered a backpack full of camping gear and scientific equipment. Boyishly slender and athletic at 45, Stock is a climber, caver, and serious reader of books about mountaineering and the natural world. He holds the enviable job title of Yosemite National Park Geologist and mostly loves the work, especially the part he was bound for that day — the study of Yosemite’s last two glaciers.
Stock and several companions started their walk in Tuolumne Meadows, the high-country jewel of Yosemite and everything that I would ever wish to find in the pastures of heaven — many square miles of grass and wildflowers surrounded by white granite domes that reflect sunshine like polished glass. Stock followed the John Muir Trail south out of those meadows into an immense U-shaped gorge called Lyell Canyon, 8 miles long and 3,000 feet deep, carved out of granite by long-vanished glaciers during dozens of ice ages. Evergreens dot the sloped walls of Lyell Canyon — straight lodgepoles down low, bent whitebarks up high.
In that drought year of 2014, dry meadow grasses carpeted the canyon floor in pale gold. Down the middle, the Lyell Fork of the Tuolumne River trickled through wide, meandering oxbows. The great irrigator of Tuolumne Meadows and drinking-water source for San Francisco, that river thunders deep in spring but flows in autumn thanks to meltwater from Stock’s destination, the Lyell Glacier.
Seven miles into Lyell Canyon, Stock kept an eye out for white rocks in the grass. If you didn’t know what to look for, you would never find those rocks, much less guess they marked a particular spot. When Stock saw them, he turned east off the John Muir Trail and down into the mostly empty channel of the Lyell Fork. He hopped across the shallows and then walked into the center of the canyon.
Stock poked around in the grass for another pile of rocks, which marked the spot where, in 1883, a geologist named Israel Russell looked 4,000 vertical feet up to the jagged summit of Mount Lyell, 13,114 feet above sea level and the tallest peak in Yosemite National Park. Standing right there, Russell took the first known photograph of the Lyell Glacier, which John Muir had found only 12 years earlier. In Russell’s photograph, 13 million square feet of ice spread like a white shawl across Mount Lyell’s black metamorphic shoulders.
Geologists and park employees have been returning to Russell’s photo point — and to the glacier itself — on a more or less regular basis ever since, replicating Russell’s images to create a scientific record 135 years old and counting. Stock has been the keeper of that tradition for over a decade, making the trip through Lyell Canyon more than 20 times to check the glacier’s vital signs. He has put gauges in runoff streams to measure meltwater trickling out of openings at the toe of the glacier. He has studied data from NASA’s Airborne Snow Observatory, an airplane outfitted with advanced sensing equipment that calculates the water volume in the Sierra snowpack and ice fields. Using much of the same technique that Muir did in 1871, Stock drove stakes into the Lyell to measure the downslope creep of ice that defines a glacier.
Like everyone who has ever studied the Lyell — and pretty much everyone who has ever studied any glacier — Stock documented shrinkage. The Lyell has lost depth and retreated upslope and broken into a smattering of white Rorschach blots that, as of 2014, amounted to about 3 million square feet of ice. In 2012, Stock had collected data showing that the main lobe of the Lyell was not flowing downhill. The pleasure of working in that quiet alpine sanctuary kept him coming back in a spirit of optimism. Still, when Stock looked through his camera’s viewfinder at the largest of the Lyell’s remaining white blots, in 2014, he was surprised to see that a familiar dark patch had grown much larger.
Stock led his companions farther south along the John Muir Trail to where it climbed up through forest toward Donohue Pass. At a wooden bridge across the river, Stock turned west off trail. Up rocky slopes, they came to the shores of an hourglass-shaped blue lake in a bowl of white stone — cooked dinner, slept in sleeping bags. In the morning, after breakfast, they hiked another 1,200 feet up to the main lobe of the Lyell, a broad and steep mass of ice in a quiet cirque of shattered rock. Stock felt like a man coming home after a long absence, comfortable and eager to catch up. He decided to have a close look at that dark patch.
“I remember noticing that it was right under an avalanche chute in the headwall below the summit,” Stock says. Perhaps it was just rock debris from some long-ago slide, embedded in the glacier surface.
The Lyell Glacier hangs at a severe angle off the mountainside. To slip and fall can mean a long, fast plummet. Stock wore crampons on his boots and carried an ice ax as he stepped onto an ice field riddled with sun cups, bathtub-sized depressions that forced him to walk along blade-thin ridges between them. Standing at the edge of the dark patch, Stock got a terrible feeling.
“I just knew. That’s bedrock. Your wishful thinking that that’s debris can’t possibly be right. The next thought was, If that’s bedrock, there can’t be much glacier left.” Letting his eye roam the periphery of the ice and visualizing mountain contours beneath the main mass of the glacier, Stock struggled to form a mental model in which the glacier maintained significant volume. He could not picture more than about 20 or 30 feet of thickness. Given the Lyell’s melt rate, it would disappear in four or five more years of drought. The shock of this realization forced Stock to confront what the data had been hinting at: The Lyell was no longer a glacier at all. Put another way, the Lyell Glacier was already dead, and Stock was the last person ever to study it.
It's a depressing story. A generation from now, today's kids will, as adults, only wonder what we did wrong. Hopefully they will vow to never repeat our mistakes. I fear that they will only choose to make even worse ones.