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That the world’s glaciers have been losing their ice is not surprising news when we know that all ecosystems are facing the consequences of climate change. However, one of the biggest consequences is being felt by the glaciers of the tropical Andes, since, according to a recent study published in ScienceThese giant ice caps, located near the equator, have shrunk to their smallest size in 11,700 years, that is, since the geological period known as the Holocene began.
“I like to think of this period as the time when human civilization developed, because it roughly begins when agriculture was invented,” Andrew Gorin, a co-author of the paper and a researcher in the Department of Earth and Planetary Sciences at the University of California, Berkeley, tells América Futura. “But it’s also a good reference period to understand our climate because if you go back beyond 11,700 years, that’s when the last ice age occurred, so it’s pretty obvious that glaciers were larger back then than they are today.”
Most of our knowledge of glaciers comes from satellite images that show how they shrink or expand. The problem is that this is historically limited data, which is why Gorin and his team used a less popular technique that allowed them to better understand the extent of these fluctuations. They took 18 samples of surface rocks from four snow-capped mountains (Zongo and Charquini in Bolivia; Pan de Azúcar in Colombia; and Queshque in Peru) and subjected them to a chemical test that tells them how long they have been exposed to the sky, to cosmic radiation.
Specifically, Gorin explains, they looked at the concentration of two isotopes—beryllium-10 and carbon-14—in each of the samples. “These are very rare chemicals that start to accumulate in rocks when they are exposed to the sky,” he says. So, if the rocks have been covered by glacial ice for less time, they will have a lower concentration of these chemicals, indicating that their exposure to the sky is recent and, therefore, the snow-capped mountains have never lost so much ice before.
“A good analogy to understand this is like when you can tell if a friend has been in the sun depending on whether they are tanned or sunburned. Although it cannot be understood literally, what we did was measure the sunburn of the rocks, just not with the sun,” explains the expert.
The work was one of cross-country, teamwork, and distance. Experts from more than six universities, including Boston College, traveled to each of these four glaciers to obtain the samples with “hammer and chisel.” They parked their cars as close as possible to the snow-capped peaks, walked for hours, took the samples, and returned with up to 20 or 25 kilos of rock in their suitcases. “In this case, I was not the one who collected them personally, but I know how it works because I have done it in glaciers in Canada and the United States,” Gorin adds. Then the rock samples were flown to his laboratory in California and analyzed. What he found had its share of concern: the glaciers of the tropical Andes, but probably also those of the entire world, are retreating much faster than expected, even decades earlier than predicted by climate science.
The data was so consistent that researchers have even gone so far as to say that the scenario these ecosystems are living in corresponds more to the Anthropocene than the Holocene. Although there is still an academic debate about whether to officially classify the Anthropocene as a geological epoch – one in which human activity is what has generated the profound changes in how the Earth works – Gorin believes that the evidence is there. “If in billions of years, when humans are no longer around, aliens were to study the history of the Earth and see the records of the rocks, their chemistry, the carbon dioxide concentration signals left behind, they would say: ‘Wow, something very strange happened here. ’ And they would probably identify this period as a unique one,” he explains.
Although glaciers in the tropical Andes became the first to “pass this alarming inter-epoch benchmark,” they will not be the only ones. Gorin, who previously published a similar study on North American glaciers, says that although they have not yet reached their historical minimum coverage in 11,700 years, “they will do so sooner rather than later.”
It is no coincidence that when people talk about climate change, the first thing that comes to mind is glaciers. “Yes, they are important because they guarantee water for hundreds of Andean communities.” But they are also important because “they function as climate aggregators,” says the expert. “Glaciers do not care about the day-to-day weather. If there was a heat wave last week or a storm a month ago, but rather they depend on long-term climate trends, on what happens to the climate in decades or hundreds of years.” That is why the fact that glaciers have retreated to dimensions not seen almost since the foundations of current human civilization were created is a strong sign.
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