Scientists investigating how Antarctica’s ice sheets retreated in the deep past have turned to a new method: studying the genes of octopuses that live in its frigid waters.
A new analysis published Thursday in Science found that geographically isolated populations of eight sea creatures intermarried freely about 125,000 years ago, signaling a corridor that there was no ice when the global temperature was the same as it is today.
The findings suggest the West Antarctic Ice Sheet (WAIS) is closer to collapse than previously thought, threatening 3.3-5 meters of sea level rise if the world doesn’t stop human-induced warming. of the 1.5 degrees Celsius target in Paris. Agreed, say the authors.
Lead author Sally Lau of James Cook University in Australia told AFP that as an evolutionary biologist focused on marine invertebrates, “I understood and then applied DNA and biology as a proxy for changes in Antarctica before.”
Turquet’s octopus makes an ideal candidate for the WAIS study, he said, because the species can be found throughout the continent and the basic information about it has already been answered by science, such as 12 years of its height, and the fact that it emerged about four. million years ago.
About half a foot (15 centimeters) long excluding arms and weighing about 1.3 pounds (600 grams), they lay relatively small, but large eggs on the bottom of the ocean floor. This means that parents must strive to ensure that their children are hatched – a lifestyle that prevents them from traveling long distances.
They are also limited by circular ocean currents, or gyres, in some of their modern habitats.
By sequencing the DNA of the genomes of 96 samples that were often collected accidentally as fishing bycatch and then left in museum storage for 33 years, Lau and colleagues found evidence of the trans-West Antarctic seaways that once connected Weddell, Amundsen and Ross. ocean
The history of genetic mixing shows that the WAIS collapsed at two distinct points — first in the middle of the Pliocene, 3-3.5 million years ago, when scientists were confident about it, and the last time in a period called the Last Interglacial, a warm spell. from 129,000 to 116,000 years ago.
“This is the last time the planet was about 1.5 degrees warmer than pre-industrial levels,” Lau said. Human activity, mainly the burning of fossil fuels, has currently increased global temperatures by 1.2C compared to the late 1700s.
“Tipping point of the coming collapse of WAIS is near”
There were some studies prior to the new paper in Science that also suggested that the WAIS collapsed in the past, but this was far from conclusive due to the relatively low resolution of the genetic and geological data.
“This study provides empirical evidence showing that the WAIS collapses when global average temperatures are similar to today’s, suggesting that the tipping point of future WAIS collapse is near,” the authors wrote.
A sea level rise of 3.3 meters would dramatically change the map of the world as we know it, submerging low-lying coastal areas everywhere.
Writing in a companion commentary, Andrea Dutton of the University of Wisconsin-Madison and Robert DeConto of the University of Massachusetts, Amherst described the new research as “pioneering,” adding that it raises interesting questions about whether the ancient history.
However, they flagged that many important questions remain unanswered – such as whether past ice collapses were caused by rising temperatures alone, or whether other variables such as changing currents of the ocean and complex interactions between ice and solid Earth are also at play.
It’s also unclear whether sea-level rise will take place over millennia or occur in more rapid leaps.
But uncertainties like these cannot be an excuse for inaction against“and this latest evidence from octopus DNA adds another card to an already unstable house of cards,” they wrote.
New news about Antarctic ice
The study comes about a month after scientists confirmed that the“on the move” after being stuck on the sea floor for 37 years, Friday. Recent satellite images show that the iceberg, called A23a, has now passed the northern tip of the Antarctic Peninsula and is heading for the Southern Ocean, according to the British Antarctic Survey.
Earlier this month, the survey was releasedtaken by the ship’s crew, including drone footage showing a pod of orcas swimming next to a large iceberg.
The iceberg weighs inaccording to data from the European Space Agency (ESA).
The iceberg, which spans nearly 4,000 square kilometers (or 1,500 square miles) in area, broke off from the Antarctic coast in 1986, but has since become land in the Weddell Sea, the BBC reports.
Meanwhile, in October, scientists revealed that they had discovered a vast, hidden landscape of hills and valleys carved by ancient rivers thatunder the Antarctic ice for millions of years.
“This is an unknown sight – no one has seen it,” Stewart Jamieson, a glaciologist at Durham University in the UK and the lead author of the study, told AFP.
The land beneath the East Antarctic Ice Sheet is less well known than the surface of Mars, Jamieson said.
The area, which spans 32,000 square kilometers (12,000 square miles), was once home to trees, forests and possibly animals.
But then the ice came and it “frozen in time,” Jamieson said.
#Octopus #DNA #reveals #Antarctic #ice #sheet #closer #collapse #previously #thought
Image Source : www.cbsnews.com