The retreat of Arctic glaciers exposes landscapes that have not seen the sun for almost 120,000 years.
These rocky horizons were probably covered with ice from the time of Amyan, a period when average temperatures were 3.6 degrees Fahrenheit (2 degrees Celsius) higher than at present, and sea levels 30 feet (9 meters) higher.
“The last century of warmth is probably more than any century before 120,000 years have passed,” said research leader Simon Pendleton, a doctoral student at the University of Colorado, at the Boulder Institute for Arctic and Alpine Studies. [See Stunning Photos of Baffin Island Glaciers]
Pendleton and his colleagues walked through these ancient landscapes as they took samples on Baffin Island in Canada. The island is surrounded by dramatic fjords, but inside it is dominated by elevated, relatively flat, tundra plains.
These tundra plains are covered with thin ice caps. Because the terrain is so flat, ice caps do not flow or slide like typical glaciers, Pendleton told Live Science magazine. Instead, they simply sit on the underlying rock and soil, keeping everything under them, like the glass of a museum cabinet.
What has been preserved is the tiny arctic plants and mosses that were last alive when ice covered the ground. According to Pendleton, when the ice melts, it reveals this ancient, delicate vegetation. Wind and water destroy long-lost plants for several months, but if researchers can get to them first, they can use radiocarbon dating to determine the age of vegetation.
Under the ice
Radiocarbon dating measures the levels of a slowly decaying carbon isotope, carbon-14. (Carbon-14 has eight neutrons in its core, not six, like normal carbon.) Because scientists know how quickly carbon-14 decays — and plants absorb carbon-14 through photosynthesis — they can use the amount of isotope in an organic sample to determine age.
Pendleton and his colleagues took 124 samples from 30 locations around the eastern island of Baffin, all within about 3 feet (1 m) from the edge of the modern ice cap – an area recently opened to melt where the remains of ancient plants had not yet been destroyed. long away.
They found that all their samples were at least as old as the oldest age that can detect radiocarbon dating: 40,000 years old. This is a direct indication that the plants were under the ice for at least that long, the researchers report on January 25 in the journal Nature Communications.
The researchers were able to confirm these measurements of vegetation by measuring the minerals in the nearby rock, which also suggested at least 40,000 years of continuous ice cover. And almost certainly, Buffin Island was buried in the ice for much longer, Pendleton said. Forty thousand years ago the world was at the height of the last ice age. According to Pendleton, if melting of ice, which has been maintained for so long, requires temperatures as warm as today, then the last period for their discovery in the Arctic is almost 120,000 years ago. Most likely, some of the landscapes presented today were buried from that warm interglacial period. [ On Ice: Stunning Images of Canadian Arctic ]
"We know that dramatic changes are taking place that will continue, but I don’t know if we expected to find evidence that we are now witnessing landscapes and temperatures similar to those in the last interglacial period, ”said Pendleton.
Pendleton said that the changes on Baffin Island are indisputable even with the naked eye. The research team took samples on the island in 2005, 2013, 2014 and 2015. According to Pendleton, the ice retreat was clear from year to year. The researchers would use GPS to pinpoint their previous sampling point, which had once been on the edge of the ice. In some places, Pendleton said, they will be at a distance of a football field from a new ice edge.
"To be able to stand there and see that change – I don't have a good word for it," said Pendleton. "It's kind of breathtaking, in a sense."
Originally posted on Living Science,