Shrinking Andean glaciers reveal 12,000-year-old rocks, signal new epoch
The glaciers in the Andes are shrinking at an unprecedented rate, revealing rocks that have not seen daylight for nearly 12,000 years. New research has shown that four glaciers in South America – Pan de Azúcar, Queshque, Zongo, and Charquini Norte – are melting much faster than previously thought due to rising temperatures caused by climate change.
Prof. Jeremy Shakun from Boston College, one of the study's authors, the results of which were published in the journal "Science," stated: "We have pretty strong evidence that these glaciers are smaller now than they have been any time in the past 11,000 years." The research team reached these conclusions by analyzing samples taken from the mountains. Experts looked for two rare isotopes in them – beryllium-10 and carbon-14, which appear on the rock surfaces when they are exposed to cosmic radiation.
The Andes are changing faster and faster
"By measuring the concentrations of these isotopes in the recently exposed bedrock we can determine how much time in the past the bedrock was exposed, which tells us how often the glaciers were smaller than today – kind of like how a sunburn can tell you how long someone was out in the sun," explains Shakun.
Andrew Gorin, a former Boston College student who conducted the research, added: "We found essentially no beryllium-10 or radiocarbon-14 in any of the 18 bedrock samples we measured in front of four tropical glaciers. That tells us there was never any significant prior exposure to cosmic radiation since these glaciers formed during the last ice age."
Scientists believe that changes in the Andean glaciers indicate an "alarming tipping point" between epochs. The Holocene is a geological epoch that began approximately 11,700 years ago, following the end of the last glaciation. Warming during this period contributed to the development of diverse ecosystems, agriculture, and more complex societies.
Now that the Andean glaciers have changed in a manner not seen during the Holocene, researchers suggest that this could signify a transition to a new epoch – the Anthropocene. "Given that modern glacier retreat is mostly due to rising temperatures – as opposed to less snowfall, or changes in cloud cover – our findings suggest the tropics have already warmed outside their Holocene range and into the Anthropocene," Shakun notes.
The expert also warns: "This is the first large region of the planet where we have strong evidence that glaciers have crossed this important benchmark – it is a ‘canary in the coalmine’ for glaciers everywhere." Although not all scientists agree that the Earth has entered a new Anthropocene epoch, the research clearly shows that our planet is going through a troubling and rapid change.
