On a spring day in 2019, Alexander Kizyakov descended the 60-meter wall of the Batagay megaslump in eastern Siberia, pausing to chisel chunks of ice-rich soil that had frozen for eons. "One of my hobbies is rock climbing," says Kizyakov, a permafrost scientist at Lomonosov Moscow State University. Colleagues next took samples of the oldest soil along the base of the cliff. Such work is too dangerous in summer, when the constant crunch of melting ice is interrupted by groans like permafrost slabs, some as large as cars, cut from the roof wall.
Known to locals as the "gateway to the underworld," Batagay is the largest thaw drop on the planet. Once it was just a ravine on a slope recorded in the 1960s, the scar has expanded year after year, as the permafrost melts and the meltwater carries away the sediment. Now more than 900 meters wide, it epitomizes the vulnerability of permafrost in the Arctic, where temperatures have soared twice as fast as the world average in the past 30 years.
But it is also a time capsule that is seducing scientists with its snapshots of ancient climates and ecosystems. "It's an amazing place," says Thomas Opel, a paleoclimatologist at the Alfred Wegener Institute. The ice and ground dates gathered at Batagay show that it contains the oldest exposed permafrost in Eurasia, spanning the last 650,000 years, Opel and colleagues reported in May at the European Union of Geosciences online general assembly. That record could reveal how permafrost and surface vegetation responded to past hot climates. "It gives us a window into the times when permafrost was stable and the times when it was eroding," says Opel.
Global warming is causing injuries across Siberia. Bursts of methane gas accumulated from thawing permafrost have pierced the desolate Russian peninsulas of Yamal and Gydan with holes tens of meters in diameter. Apartment buildings are trading and collapsing on unstable terrain, causing around $ 2 billion a year in damage to the Russian economy. Forest fires over the past three summers have burned millions of hectares across Siberia, covering the earth with dark soot and coal that absorb heat and accelerate melting.
The intensification of this year's fires was a heat wave that roasted Siberia during the first half of 2020. On June 20, the city of Verkhoyansk, just 75 kilometers from Batagay and one of the coldest inhabited places on Earth , reached 38 ° C, the highest temperature. Ever recorded in the Arctic. Record heat "would have been effectively impossible without human-induced climate change," said the authors of a July 15 study by World Weather Attribution, a collaboration of meteorologists analyzing the possible influence of climate change on extreme weather events. .
A permanent question is how much carbon will the thawing soil release into the atmosphere and whether the lush growth of Arctic plants in the hot climate will absorb enough carbon to offset the release. The Arctic may have already reached a tipping point: Based on observations at 100 field sites, northern permafrost released on average about 600 million tons more carbon than vegetation absorbed each year between 2003 and 2017, they estimated. scientists in October 2019.
Permafrost scientists Alexander Kizyakov and Dmitry Ukhin rappel down the 60-meter-high wall to collect increasingly frozen ground.
Scientists are venturing to Batagay in annual campaigns to learn what he can say about it. The tours, organized by the Institute of Northern Applied Ecology in Yakutsk, are not for the faint of heart. In 2014, Kseniia Ashastina traveled 3 kilometers of mosquito-infested forest to reach the edge of the headland. "You hear a lot of creaking as you get closer, and suddenly there are no trees and you're standing on a ledge," says Ashastina, a paleobotany at the Max Planck Institute for the Science of Human History. She and her colleagues at the Senckenberg Research Institute and the Museum of Natural History stayed with Siberian Indians, Evens and Sakha, some of whom fear the megagam. "They say they are eating up their land, swallowing the trees and their sacred places," she says.
To find out the age of the exposed permafrost, Opel's team relies on luminescence dating, which reveals the last time minerals in the soil saw daylight, and a new Russian technique for dating chlorine on ice. The dates allow them to match the soil layers to the known climate record, while the abundance of two ice wedge-trapped isotopes, oxygen-18 and deuterium, are indicators of local temperatures. Batagay's analysis of soil composition should provide information on how much carbon dried permafrost over millennia.
Permafrost also provides a glimpse of ancient Arctic ecosystems. By sampling trapped plant debris, the team learned that during the last ice age, when winter temperatures dropped even lower than in modern times, the vegetation was surprisingly lush, supporting woolly mammoths, woolly rhinos, and other herbivores. now disappeared in a steppe prairie ecosystem. . "It was a paradise for animals that feed," says Ashastina.
Sometimes the remains of these lost creatures fall from the wall in exquisite condition. In 2018, scientists recovered a young ginger-colored Lena horse (Equus lenensis), an extinct relative of the Yakutian horse, with intact soft tissue. Scientists hope to find a living cell to be able to clone the 42,000-year-old foal. Part of his preserved muscle is particularly promising, says P. Olof Olsson, a molecular biologist at the Abu Dhabi Biotech Research Foundation, which is joining the effort with the Federal University of Northeast Yakutsk. "I am skeptically optimistic," says Olsson. "At least, it's not impossible."
As the elements separate further from Batagay's mega-drop, it could transport scientists deeper into time. Glaciers clear the ground as they go, but they largely overlooked Siberia during the last glaciations, leaving permafrost in some areas hundreds of meters thick. For decades, as hot summers liquefied its ice-rich soil, Batagay's headwaters advanced about 10 meters per year, says Frank Guenther, a permafrost researcher at the University of Potsdam. Since 2016, he says, that rate has increased from 12 to 14 meters per year. It is more difficult to determine how fast the depression is deepening, and therefore how much further back in time the melt is penetrating. The oldest permafrost ever dated, from the Canadian Yukon Territory, is 740,000 years old. As much as climate watchers may shrink at the idea, several more grilled Siberian summers could push the Batagay mega-range to claim another record.
