Octopus DNA reveals Antarctic ice sheet collapse is “close.”

By | December 22, 2023

Scientists studying how Antarctica’s ice sheets retreated in the deep past have turned to an innovative approach: studying the genes of octopuses that live in the cold waters.

A new analysis published Thursday in Science shows that geographically isolated populations of the eight-limbed marine animals mated freely about 125,000 years ago, suggesting an ice-free corridor during a period when global temperatures were similar to today.

The findings suggest the West Antarctic Ice Sheet (WAIS) is closer to collapse than previously thought, threatening long-term sea level rise of 3.3 to 5 meters if the world fails to stem human-induced warming within 1.5 degrees Celsius of the Paris target. Agreed, according to the authors.

Lead author Sally Lau from James Cook University in Australia told AFP that, as an evolutionary biologist focusing on marine invertebrates, I “understand DNA and biology and then apply it as a measure of past changes in Antarctica.”

Turquet’s octopus was an ideal candidate for studying WAIS, she said, because the species is found throughout the continent and basic information about it has already been answered by science, such as its 12-year lifespan and the fact that the species is so n emerged four years ago. million years ago.

About half a foot (15 centimeters) long excluding the arms and weighing about 1.3 pounds (600 grams), they lay relatively few, but large eggs at the bottom of the seabed. This means that parents must put in significant effort to ensure that their offspring hatch – a lifestyle that prevents them from traveling too far away.

In some of their modern habitats they are also restricted by circular ocean currents, or gyres.

By sequencing the DNA from the genomes of 96 samples that were generally collected unintentionally as fishing bycatch and then left in museum storage over the course of 33 years, Lau and colleagues found evidence of transwest Antarctic seaways that once connected the Weddell , Amundsen and Ross linked together. seas.

The history of genetic admixture indicated that WAIS collapsed at two separate points: first in the mid-Pliocene, 3-3.5 million years ago, which scientists were already confident about, and the last time in a period called the Last Interglacial is called a warm period. from 129,000 to 116,000 years ago.

“This was the last time the planet was about 1.5 degrees warmer than pre-industrial levels,” says Lau. Human activity, mainly the burning of fossil fuels, has so far increased global temperatures by 1.2 degrees Celsius compared to the late 18th century.

“The tipping point of future WAIS collapse is close”

There were a handful of studies prior to the new Science article that also suggested that WAIS had collapsed some time in the past, but these were far from conclusive due to the relatively lower resolution genetic and geological data.

“This study provides empirical evidence indicating that the WAIS collapsed when global average temperatures were similar to today, suggesting that the tipping point of future WAIS collapse is close,” the authors wrote.

A sea level rise of 3.3 meters would drastically change the world map as we know it, flooding low-lying coastal areas everywhere.

In an accompanying commentary piece, Andrea Dutton of the University of Wisconsin-Madison and Robert DeConto of the University of Massachusetts Amherst described the new research as “groundbreaking,” adding that it raised intriguing questions about whether ancient history will repeat itself.

However, they pointed out that several important questions remained unanswered – such as whether past ice sheet collapse was caused solely by rising temperatures, or whether other variables, such as changing ocean currents and complex interactions between ice and the solid Earth, also played a role. played a role.

It is also not clear whether sea level rise will continue over millennia or occur in faster jumps.

But uncertainties like these should not be an excuse for doing nothing about them climate change “and this latest piece of octopus DNA evidence adds another card to an already unstable house of cards,” they wrote.

Recent news about Antarctic ice

The study comes about a month after scientists confirmed that the the world’s largest iceberg was “on its way” on Friday after being stuck on the ocean floor for 37 years. Recent satellite images show that the iceberg, called A23a, is now moving past the northern tip of the Antarctic Peninsula and towards the Southern Ocean, according to the British Antarctic Survey.

The research was published earlier this month dramatic video taken by the ship’s crew, including drone footage showing a pod of killer whales swimming next to the massive iceberg.

The iceberg weighs approx almost 1 trillion tonsThis is evident from data from the European Space Agency (ESA).

The iceberg, which covers an area of ​​almost 4,000 square kilometers (or 1,500 square miles), split off the Antarctic coastline in 1986 but subsequently came aground in the Weddell Sea, the BBC reported.

Meanwhile, scientists revealed in October that they had discovered a vast, hidden landscape of hills and valleys, carved out by ancient rivers that “frozen in time” millions of years under the Antarctic ice.

“It’s an undiscovered landscape – no one has seen it,” Stewart Jamieson, a glaciologist at Britain’s Durham University and the study’s lead author, told AFP.

The land beneath the East Antarctic Ice Sheet is less known than the surface of Mars, Jamieson said.

The area, which extends over 32,000 square kilometers (12,000 sq mi), was once home to trees, forests and probably animals.

But then the ice came and it was “frozen in time,” Jamieson said.

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