Octopus DNA tells scientists that total collapse of the Antarctic ice sheet is "close"

Scientists have long studied Antarctica’s icy frontiers to predict how our warming world could reshape coastlines everywhere. Their attention recently turned to an unexpected ally: an Antarctic octopus that inhabits the chilly waters around the continent.

This Antarctic octopus species, known among experts for its unique distribution, has offered vital clues about a time in the past when ice retreated, ocean passages opened, and sea levels rose.

Its DNA carries signals of events that may happen again if global temperatures continue to rise.

Antarctic ice and Turquet’s octopus

Lead author Sally Lau of James Cook University in Australia explained that the genetic markers in this marine invertebrate link to shifts in Antarctica’s ice sheets thousands of years ago.

She said, “I understand and then apply DNA and biology as a proxy of changes to Antarctica in the past.”

Researchers focused on a species commonly called Turquet’s octopus (Pareledone turqueti), which is widespread around Antarctica and has been recognized for around four million years.

This cephalopod measures about half-a-foot (15 centimeters) long excluding its arms and weighs approximately 1.3 pounds (600 grams).

Because it lays relatively few large eggs that must be tended carefully on the seafloor, the animal tends not to wander far, making each population’s genetic signatures more distinct. Circular sea currents trap different groups in separate regions.

Understanding Turquet’s octopus – the basics

Known for its adaptability to the icy environment, Turquet’s octopus (Pareledone turqueti) is a master of camouflage, using its ability to change color and texture to blend into its surroundings.

It thrives at depths of around 200 to 500 meters, where sunlight barely reaches, making it an elusive creature for scientists to study.

Despite living in such a harsh environment, Turquet’s octopus is well-equipped to survive, thanks to its remarkable physiology and unique behaviors.

For such a small creature, it plays an outsized role in the Antarctic ecosystem. It’s a predator, feeding on smaller fish and invertebrates, and is an important part of the food web.

Octopus DNA and Antarctic ice sheet melt

Scientists analyzed genetic data across 96 samples taken over three decades from museum collections. Findings showed clear evidence that this octopus once traveled between the Weddell, Amundsen, and Ross seas.

The only way for that to have happened was if massive expanses of ice vanished, opening channels where water (and octopuses) could move freely.

Genetic mixing placed those moments of ice sheet collapse in the mid-Pliocene, roughly 3-3.5 million years ago, and again during the Last Interglacial period, between 129,000 and 116,000 years ago.

“This was the last time the planet was around 1.5 degrees warmer than pre-industrial levels,” said Lau.

Why does any of this matter?

Scientists report that human activity has so far raised global temperatures by 1.2C relative to late 1700s benchmarks.

Experts warn that the West Antarctic Ice Sheet (WAIS) could be unstable under current climate targets, with the potential to add around 10-15 feet (3.3-5 meters) of sea level rise long term.

This study provides empirical evidence indicating that the WAIS collapsed when the global mean temperature was similar to that of today, suggesting that the tipping point of future WAIS collapse is “close.”

Another contribution described the analysis as “pioneering,” noting that “and this latest piece of evidence from octopus DNA stacks one more card on an already unstable house of cards.”

Many more questions remain

The researchers emphasized in their study that many factors can influence how quickly an ice sheet melts, including changing ocean currents and the interaction between ice and the underlying bedrock.

Additional mysteries include whether the sea level rise would stretch over many centuries or appear in a series of faster surges.

They also highlighted ongoing research into whether various forces, beyond warmer temperatures, triggered the previous collapses.

Low-lying coastlines face the brunt of these possibilities. Even a modest rise can reshape communities and infrastructure on a global scale.

Researchers point to growing data on past sea levels, combined with the new genetic work, as motivation for further studies into climate dynamics.

More clues from the Southern Ocean

Questions about Antarctica’s future intersect with the behavior of the Southern Ocean.

Recent analysis led by Professor Simon Josey, an expert on ocean-atmosphere interaction at the UK’s National Oceanography Centre (NOC), connected shrinking Antarctic sea ice to more powerful winter storms and major changes in ocean structure.

According to the findings, years with minimal sea ice are likely to experience heightened storm activity and notable shifts in how heat and nutrients move through the water.

One crucial observation centers on water density. When surface waters lose heat, they become heavier and sink more readily.

“The massive increase in ocean heat loss to the atmosphere is increasing the density of water at the sea surface to values not previously seen,” said Professor Josey.

This diving of denser water can alter how the ocean circulates, which then affects temperatures and nutrient flows over great distances.

Antarctic ice, Turquet’s octopus, and the future

Long-term changes in these deep currents might ripple through wider ocean basins, impacting weather patterns on other continents.

While many questions remain, scientists who investigate these signals from both ice sheets and marine life say the findings underscore the delicate balance of the polar environment.

Observations from octopus DNA, past sea level data, and new measurements of ocean heat exchange all add to the conversation about how warming may influence global coastlines and climates.

Researchers continue searching for more clues. Some look to ocean sediments, others to geological evidence. Each piece offers a small glimpse into cycles of warming and cooling that have repeated over millennia.

The common thread is the realization that Antarctica, though distant for many, is entwined with planetary systems in ways that affect all of us.

The full study was published in the journal Science.

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