Scientists claim that a 4 million year old octopus' DNA has a clue about increasing sea levels

 February 04, 2023

With concerns that global warming may soon drive the ice sheet towards rapid melting, which would lock in increasing sea levels over millennia, the ice sheet currently carries enough water to increase sea levels by 3 to 4 metres.

11 scientists, including biologists, geneticists, glaciologists, computer scientists, and ice-sheet modellers, used a creative technique to examine the genetics of Turquet's octopus, a species that has existed in and near the Antarctic continent for about 4 million years.

96 octopuses gathered over a period of three decades from various parts of the continent had their genetic material sampled.

The DNA of the octopus contains memories of its past, including when and how various populations moved and mixed, exchanging genetic material.

The only logical path, according to the researchers, was a seaway between the south Weddell Sea and the Ross Sea, by which some octopus populations on different sides of the West Antarctic Ice Sheet had interacted with some 125,000 years ago.

The study's principal investigator, Dr. Sally Lau, a geneticist at James Cook University, remarked, "That could have only happened if the ice sheet had entirely disintegrated."

The study is being peer-reviewed by a publication, but Lau said she decided to make it public because she wanted the scientific community to have early access and because the findings were urgent.

According to her, she was able to identify the time when octopuses in the south Weddell Sea and the Ross Sea were mixing by using information on the changes in the octopus' DNA as a kind of clock.

The melting of the ice sheet could become "self-sustaining" and last for millennia or more, according to Prof. Nick Golledge, a co-author of the study from Victoria University of Wellington in New Zealand.

Approximately 1,500 to 2,000 metres below the top of the present-day ice sheet, according to him, is where the octopuses are likely to have travelled. The depth of that waterway was around 1,000 metres, albeit it was shallower closer to the margin.

He remarked, "It's a large seaway for species to transit and a sizeable ocean segment."

The rate of ice loss from west Antarctica, he claimed, had been accelerating during the last two decades.

The last interglacial was between 0.5C and 1.5C warmer than the time right before the industrial revolution, according to the most recent UN climate assessment. Sea levels were 5 to 10 metres greater than they are now.

The West Antarctic Ice Sheet may be doomed to collapse, according to the authors of the octopus study, even if global warming is limited to 1.5C, the most aggressive target set by the Paris Climate Agreement.

Professor Nathan Bindoff, an oceanographer and expert on Antarctica at the University of Tasmania, stated that with sea levels this high, scientists are convinced that the melting of the West Antarctic Ice Sheet is a major factor in the sea levels' rise.

Using octopus DNA was "the last way I would have imagined of having evidence of big sea level changes originating from the collapse of the West Antarctic Ice Sheet," according to Bindoff, who was not involved in the study.

"The Earth would suffer very significant consequences if that ice sheet disappeared. If this [octopus research] is accurate, the Earth system has sensitivities that result in global sea level rise.

Bindoff stated in the most recent UN climate report that one of the biggest unknowns regarding potential sea level rise is related to the West Antarctic Ice Sheet.

According to him, 65 million people reside on small island states and over 670 million people dwell in low-lying areas worldwide.

This article, according to him, is yet another piece of data that lessens the uncertainty surrounding the history of the ice sheet, which is crucial for how we think about the future.

Although there is evidence that the ice sheet fell millions of years ago, Prof. Richard Alley of Penn State University remarked, "we still aren't convinced whether the ice sheet deglaciated during the most recent interglacial."

He called the octopus research "interesting and relevant" and claimed that it supported claims that the ice sheet was lost during the most recent interglacial period.