Glaciers are retreating around the world as the planet warms, but scientists have debated how severe the shrinkage is compared to periodic glacial advances and retreats since the end of the Ice Age about 12,000 years ago.
A new study of four glaciers dotting the high Andes in Colombia, Peru and Bolivia shows that, at least in the tropics, the retreat is unprecedented. The glaciers are smaller than they have been in more than 11,700 years, the beginning of a warm interglacial period geologists refer to as the Holocene.
According to Andrew Gorin, a University of California, Berkeley, graduate student in the department of earth & planetary science and first author of the study, published today (Aug. 1) in Science, this likely means that the glaciers are smaller than they have been in the past 125,000 years, before the most recent glacial era began 120,000 years ago. The data, however, aren’t precise enough to allow extrapolation that far into the past.
“The complexities of our technique are such that we don’t have the resolution to see past about 12,000 years ago,” said Gorin, who began the research as a master’s degree student working with study leader Jeremy Shakun at Boston College. “However, a reasonable person might infer that these glaciers are actually now smaller than they have ever been since at least the last interglacial period, about 125,000 years ago.”