A new study that analyses octopus DNA has discovered that 120,000 years ago, when global temperatures were similar to today, it is likely the West Antarctic Ice Sheet collapsed.

Researchers from The University of Western Australia, James Cook University and the Western Australian Museum led the study published in the journal Science.

Dr Nerida Wilson, from UWA’s School of Biological Sciences and the WA Museum, said the team compared the genetic profiles of Turquet’s octopus found in the Weddell, Amundsen and Ross seas and found populations on opposite sides of the West Antarctic Ice Sheet mixed about 120,000 years ago. 

Image: Turquet’s octopus. Credit: Dave Barnes

“The ability of the populations to mix and exchange genes would only be possible if the West Antarctic Ice Sheet had collapsed entirely, opening seaways the octopus could use to connect to each other,” Dr Wilson said.

“The historical genetic link among these populations is revealed by looking at the DNA of octopus from recent times around Antarctica.”

During the Last Interglacial period the global average temperatures were 0.5 to 1.5C warmer than preindustrial levels and the global sea level was five to 10m higher than today but whether the West Antarctic Ice Sheet collapsed during this time had been unclear until now.

Lead investigator Professor Jan Strugnell, from James Cook University, said understanding how the West Antarctic Ice Sheet was configured in the past, when global temperatures were similar to today, would help us improve future global sea level rise projections.

The findings suggest that even under global warming of 1.5C – the target under the Paris Climate Agreement is to keep global average warming to well below 2C, and ideally lower than 1.5C – the West Antarctic Ice Sheet could collapse.

“The West Antarctic Ice Sheet is critical to estimations as it is currently Antarctica’s biggest contributor to global sea level rise,” Dr Wilson said.

“A complete collapse could raise global sea levels by approximately three to five metres.”

The results of the study, from ARC’s Securing Antarctica’s Environmental Future, will help improve future global sea level rise projections and support decision-making around climate change adaptations around the world.