ice sheet collapse” title=”Turquet’s octopus (Pareledone turqueti) lives on the seafloor around Antarctica. Credit: Dave Barnes/British Antarctic Survey” width=”800″ height=”528″/>
Turquet’s Octopus: The Key to Antarctic Ice Melts
If we want to understand the future, it’s often useful to look at the past. And even more useful if you use octopus DNA to peer into worlds long gone.
About 125,000 years ago, the Earth was in its last warm period between ice ages. Global average temperatures during this interglacial period were about 0.5–1.5° C warmer than pre-industrial levels.
This has strong parallels with our time. For a third of 2023, the Earth’s temperature has been 1.5° C warmer than the pre-industrial era, driven by climate change.
For almost 50 years physical scientists have sought the answer to whether or not the vast West Antarctic Ice Sheet collapsed the last time global temperatures were this high. Rather than relying only on geological sampling, we turned to the DNA of a small Antarctic octopus for clues to the deep past.
The DNA had an answer. Our new research shows yes, it most likely collapsed.
The West Antarctic Ice Sheet is very susceptible to warming. If it melts, it has enough water to raise global sea levels by 3.3 to 5 meters.
Of Octopuses and Giant Ice Sheets
Sediment records and other ice cores show us that the ice sheet retreated at some point during the last ~1 million years in the late Pleistocene, but the exact timing and extent of any collapse remain ambiguous. To get a more precise answer, we looked to cephalopod genetics.
Every organism’s DNA is a history book, and we now have the technology to read it. We can use DNA to look back in time and pinpoint when different populations of animals were interbreeding.
Turquet’s octopus (Pareledone turqueti) is fairly small, weighing up to 600 grams. They live on the sea floor all around Antarctica, but individuals don’t move far from home. Antarctica is so vast that populations in different regions cannot usually interbreed.
Deep under West Antarctica lies gaps in the rocks. At present, these are filled by the ice sheet, making the Weddell, Amundsen and Ross seas separate from each other.
If the ice melted, seaways would open up and connect these isolated basins. Octopuses could directly migrate into these regions and the evidence of their breeding would be laid down in DNA.
But if the ice sheet didn’t melt, we would only see evidence of breeding between octopus populations along the circumference of the continent.
We compared DNA patterns in Turquet octopus genomes all around Antarctica to see if there were direct and unique connections between octopus populations in the Weddell, Amundsen and Ross seas. We used statistical models to figure out whether these connections could be explained by their present day connections around the Antarctic coastline.
The story was clear in the DNA: yes,
