Octopus DNA reveals collapse of Antarctic ice sheet is "close"

Examining the genomes of octopuses that inhabit Antarctica's frigid seas is an inventive method used by researchers to try and understand how the continent's ice sheets receded in the distant past.

Eight-limbed sea animals mated easily across geographically dispersed populations around 125,000 years ago, indicating an ice-free corridor during a time when global temperatures were comparable to those of today, according to a new research published in Science on Thursday.

The results indicate that the West Antarctic Ice Sheet (WAIS) may be more vulnerable to collapse than previously believed, posing a hazard to long-term sea level rise of 3.3-5 meters if global warming from human activity cannot be contained to the 1.5 degrees Celsius limit set by the Paris Agreement, according to the authors.

As an evolutionary biologist studying marine invertebrates, lead scientist Sally Lau of James Cook University in Australia told AFP, "I understand and then apply DNA and biology as a proxy of changes to Antarctica in the past."

Turquet's octopus, she said, was a prime option for investigating WAIS as the species is widespread over the continent and basic questions about it, including its 12-year life span and its estimated four million-year evolutionary history, had already been resolved by science.

They measure around 1.3 pounds (600 kilos) and are about half a foot (15 cm) long, excluding the limbs. They deposit comparatively few, but huge, eggs on the seabed. This implies that parents have to work very hard to ensure that their kids hatch and have a lifestyle that keeps them from going too far away.

In several of their contemporary environments, they are also restricted by gyres, or circular marine currents.

Lau and colleagues discovered evidence of trans-West Antarctic seaways that formerly connected the Weddell, Amundsen, and Ross seas by sequencing the genomes of 96 samples, most of which were unintentionally acquired as fishing bycatch and then stored in museums for 33 years.

The history of genetic mixing suggested that WAIS collapsed twice: first during the Last Interglacial, a warm era that lasted from 129,000 to 116,000 years ago, during the mid-Pliocene, around 3-3.5 million years ago, about which scientists were previously certain.

"This was the last time the planet was around 1.5 degrees warmer than pre-industrial levels," Lau stated. In comparison to the late 1700s, human activity—primarily the combustion of fossil fuels—has boosted global temperatures by 1.2C thus far.

"Tipping point of future WAIS collapse is close"

Before the recent Science study, a few studies also showed that WAIS collapsed at some point in the past, but the relatively poor resolution genetic and geological data made them far from definitive.

"This study provides empirical evidence indicating that the WAIS collapsed when the global mean temperature was similar to that of today, suggesting that the tipping point of future WAIS collapse is close," the authors stated.

A 3.3-meter rise in sea level will completely change the world map, engulfing all low-lying coastal communities.

The new research is "pioneering," according to Andrea Dutton of the University of Wisconsin-Madison and Robert DeConto of the University of Massachusetts, Amherst, who wrote an accompanying opinion article. They also said that the discovery raised interesting concerns regarding whether or not past history will be reproduced.

They did, however, draw attention to the fact that a number of important concerns remained unsolved, such as whether rising temperatures alone were responsible for the last ice sheet collapse or if other factors, such as shifting ocean currents and intricate interactions between ice and solid Earth, were also at play.

Furthermore, it's unclear if the rise in sea level will happen gradually over millennia or more quickly.

They said, "and this latest piece of evidence from octopus DNA stacks one more card on an already unstable house of cards," but uncertainties like this cannot be used as an excuse for inactivity against climate change.

Current events pertaining to Antarctic ice

The study was conducted around one month after scientists announced on Friday that the largest iceberg in the world was "on the move" after being cemented to the ocean floor for 37 years. The British Antarctic Survey reports that the iceberg, known as A23a, is currently traveling past the northern point of the Antarctic Peninsula and toward the Southern Ocean based on recent satellite pictures.

Dramatic footage shot by the ship's crew, including drone footage of a pod of orcas swimming adjacent to the gigantic iceberg, was made public earlier this month by the survey.

The European Space Agency (ESA) has provided data indicating that the weight of the iceberg is around one trillion tons.

The iceberg broke off from the Antarctic coast in 1986, covering an area of over 4,000 square kilometers (or 1,500 square miles), but it later grounded in the Weddell Sea, according to the BBC.

A massive, hidden landscape of hills and valleys sculpted by ancient rivers that have been "frozen in time" beneath the Antarctic ice for millions of years was uncovered by geologists in October.

The study's principal author, Stewart Jamieson, a glaciologist at Durham University in the United Kingdom, told AFP that "no one has laid eyes on it."

According to Jamieson, the region underneath the East Antarctic Ice Sheet is not as well-known as the surface of Mars.

The region, which covers 32,000 square kilometers (12,000 square miles), was formerly home to woods, trees, and maybe even some wildlife.

However, Jamieson stated that it was "frozen in time" when the ice appeared.