Sensitivity to the melting of the West Antarctic ice sheet can be read from octopus DNA

What will the West Antarctica ice sheet do as global temperatures increasingly rise? It's a question that has preoccupied climate scientists around the world for decades. If the ice sheet melted completely, sea levels could rise by five metres. But no one understands exactly how the West Antarctic Ice Sheet is responding to global warming.

In the DNA of a small octopus from the Southern Ocean, researchers found evidence that a temperature rise of about 1 to 1.5 degrees above pre-industrial levels is enough to cause the West Antarctic ice sheet to collapse. The group, led by evolutionary geneticist Sally Lau from James Cook University in Australia, published Analysis last month Sciences.

Of the three major ice sheets on Earth (Greenland, East and West Antarctica), West Antarctica is the most sensitive to rising air and ocean temperatures. The hat is more than 2,000 meters thick in some places, and is in direct contact with warm ocean currents.

To learn something about what the ice sheet will do in the future, researchers are looking to the past. During the last ice age (a short interval between two ice ages), 130,000 to 115,000 years ago, global temperatures averaged 1 to 1.5 degrees Celsius above pre-industrial levels. Due to the melting of the glaciers, the sea level at that time was five to ten meters higher than it is now.

Short as a pencil

How much of that came from the melting Western Antarctic Ice Sheet? To answer this, researchers study the canopy itself and the sediments and use computer models. Various studies suggest that the West Antarctic ice sheet has collapsed completely, but much is uncertain.

Lau's team has now used a new data set: 96 octopuses from different groups of the species Pareledon turketti. These octopuses – with bodies as short as a pencil – crawl across the seafloor in the waters surrounding Antarctica. Except for a few eggs carried with the current, octopuses do not wander far from home. The Ross Sea and Weddell Sea populations remain separated by the Western Antarctic Ice Sheet.

But octopus DNA showed that the two groups once lived intermingled. According to the researchers, this indicates that the passage between the two seas was previously open, thus melting the ice sheet. According to the researchers, the time of mixing corresponds to the last ice age.

“An interesting study,” answers Francesca Sangiorgi. She is an earth scientist at Utrecht University and is researching the melting of the West Antarctic ice sheet by analyzing fossil microalgae in drill cores, but she was not involved in this study. “Researchers provide new evidence for what previous studies have suggested, but it is not enough yet. Researchers are trying to link a period to the melting of the ice sheet, and there is a lot of uncertainty. We will soon have more clarity on this with our analysis of the sediments.”

The Earth's temperature has now risen by about 1.2 degrees Celsius. It is impossible to say whether the same melting could happen again.

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