New research shows that the small glaciers that overlook Yosemite National Park predate humans coming to North America. And soon they’ll be gone.
By Hillel Aron, Courthouse News Service
The glaciers that have carved the Sierra Nevada mountain range for millions of years will be gone by 2100, according to a paper published Wednesday in the journal Science Advances.
Humans have never looked up at Mount Lyell, the highest point in Yosemite National Park, and not seen ice. There have been glaciers in the region for 30,000 years.
Climate change is sort of this abstract and a nebulous problem, in a lot of ways,” said the paper’s author, Andrew Jones, a geologist and PhD candidate at the University of Wisconsin-Madison. “But glaciers are tangible. A glacier is sort of a touchstone between the past and the present.”
Since 1880, the average temperature on Earth has increased dramatically, by at least 1.8 degrees Fahrenheit, and by as much as 2.2 degrees Fahrenheit — largely the result of humans causing unprecedented levels of greenhouse gasses to be released into the atmosphere due to industrialization. The world is getting hotter; most people can see that on their iPhone’s weather app, or their summer electricity bill. But among the most concerning changes, as well as the most visible ones, are the melting of the polar ice caps and the glaciers.
The glaciers high up in the Sierra Nevada mountains are not typical. They are especially small and much closer to the equator than other glaciers. They nestle on the side of the mountains in the bowl-shaped cirque, shielded from the sun for much the day.
Their loss is more than a symbolic one. Glaciers in the Sierra Nevada mountains serve as a kind of reservoir of last resort, a bit like that extra 10% or so of gas your car has after it tells you it’s empty. Though they don’t supply all that much drinking water, they do serve us in times of extreme drought.
Though researchers have long known that the Sierra Nevada glaciers were slowly disappearing, they didn’t know how long they have been around — until now. In order to find out, Jones took samples of four glaciers — Conness, Maclure, Lyell, and Palisade — in and around Yosemite, and analyzed them using cosmogenic nuclide dating.
“You literally put one hand on the ice and you’re standing on bedrock that has been exposed by the retreating glacier and we can actually date when, in the past, that bedrock was exposed,” Jones said. “We can actually measure the time the rock has been sitting on the surface of the Earth, not covered by glacier. In this case, it was no time at all. It’s just been buried.”
The Sierra Nevada glaciers will be among the first in the world to vanish. And though glaciers have changed throughout the last few millennia, Jones says that the melting of these unusually small and southern ones are a significant marker. They’ve clung frozen to the mountain since before humans came to North America. Soon they’ll be gone.
“This shows we’re exiting the balance of normal,” Jones said.
