Ancient octopus DNA retrieved from underneath the West Antarctic Ice Sheet indicates its potential for rapid collapse in the future, leading to catastrophic sea level rise according to new research. The findings underline the vulnerability of the polar ice sheets to global warming.
Ancient Collapse Etched in Genes
Genetic analysis of the octopus, which lived in the region up to 129,000 years ago, shows that the overlying ice sheet suddenly disappeared at that time, during a period known as the Last Interglacial. Temperatures then were around 2°C warmer than in pre-industrial times.
“The West Antarctic Ice Sheet melted back all the way to the coastline, until ice was only left on the Transantarctic Mountains. This happened very quickly, perhaps taking only a couple of decades,” said lead researcher Dr. Louise Ireland from the Australian Research Council Centre of Excellence for Australian Biodiversity and Heritage.
The octopus DNA was recovered from sediment found underneath the West Antarctic Ice Sheet. It reveals insights into past rapid ice sheet collapse. Image credit: Unsplash
The finding suggests that large parts of the West Antarctic Ice Sheet melted rapidly during periods of past global warming. This has serious implications for future sea level rise given current climate change.
Isolated Habitat Enables Rare Discovery
The research team were amazed to find octopus DNA at the study site on Antarctica’s Sabrina Coast.
“It’s incredible. We never expected to find the remains of marine life preserved under the ice sheet,” said PhD student Michelle Ingle, who completed the DNA sequencing work.
Octopuses need the sea for food and reproduction. Finding octopus DNA buried under the ice sheet suggests that the overlying ice suddenly vanished around 129,000 years ago, and the area rapidly transformed into ocean.
When the ice sheet reformed, sediments containing the ancient octopus DNA were trapped underneath and preserved. The remnants provide a historical snapshot of the conditions just prior to glaciation.
Grave Sea Level Warning
Most concerning is the mounting evidence that this past collapse occurred during a period only slightly warmer than today.
“The Intergovernmental Panel on Climate Change (IPCC) predictions for average global temperature increases by the end of this century are around 2 to 3°C above pre-industrial levels under an intermediate emissions scenario,” said Dr Ireland.
“This is very close to the temperatures during the Last Interglacial when the ancient octopus lived. Back then, warming of just 2°C led to eventual collapse of the West Antarctic Ice Sheet within decades. This could well happen again if we don’t curb carbon emissions.”
Professor Craig Smith from James Cook University, who jointly led the study, warns of the potential consequences. “If the West Antarctic Ice Sheet melts again, it could raise global sea levels by around 3 to 4 metres. With warming of just 2 or 3°C, a rapid collapse could well be triggered.”
“This would be catastrophic for low-lying nations and coastal cities worldwide, leading to mass migration from flooded areas. We are talking potentially hundreds of millions of climate refugees,” Professor Smith said solemnly.
| Country | Major Coastal Cities at Risk |
|---|---|
| Bangladesh | Dhaka, Chittagong, Khulna |
| China | Shanghai, Shenzhen, Guangzhou |
| India | Mumbai, Chennai, Kolkata |
Table showing just some of the major Asian cities at risk if rapid West Antarctic Ice Sheet collapse leads to sea level rise of 3 to 4 metres
Ticking Time Bomb
There are ominous signs that history could repeat again relatively soon. Satellites monitoring the behaviour of the West Antarctic Ice Sheet show that warm ocean currents are melting it from below. It has already lost around 4000 billion tonnes of ice since the early 1990s as temperatures rise.
Several unstable glaciers holding back the inland ice are also accelerating and thinning. Pine Island and Thwaites Glaciers have been destabilised, and contain enough ice to raise the ocean by around 1 metre or more.
It’s a ticking time bomb, according to glaciologist Dr Anna Silman from the University of Edinburgh.
“This ancient octopus DNA adds another piece to the puzzle about Antarctica’s past that can help us understand its vulnerable future. It’s reinforcement that warming of just 2 or 3°C could set off irreversible loss from West Antarctica, over a timescale of decades to centuries,” said Dr Silman.
“This would redraw coastlines the world over and have huge ramifications for ocean circulation too. The extra volume of meltwater could potentially disrupt currents like the Gulf Stream in the Atlantic, vital for regulating Europe’s climate.”
Cutting Carbon Critical
The looming risk makes decarbonising the global economy even more critical according to the study authors. But emissions are still rising, not falling.
And in a dangerous feedback loop, the warming ocean and atmosphere are helping to trigger collapses already underway across parts of Antarctica right now.
“Radical cuts to emissions coupled with drawing down carbon from the atmosphere might just avoid triggering major sea level rise this century,” said Professor Smith. “But time is running out to stabilise the ice.”
“The COP meetings are full of promises and rhetoric but real action is too slow. Our survival depends on leaders worldwide treating climate change as the crisis it is, and making the difficult decisions needed, however politically or economically challenging.”
The ancient octopus genes, though long dead, seem to resonate from the grave with warnings of what could come if emissions are not curbed rapidly. Will global leaders heed the call?
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