Scientists have made a startling discovery using DNA preserved in octopus shells found deep in the ocean near Antarctica. Analysis of the DNA shows that 129,000 years ago, the West Antarctic Ice Sheet underwent rapid collapse, causing global sea levels to rise over 3 meters higher than today. This revelation carries grave warnings about the fate of the Antarctic ice sheet in our warming world.
Ancient Octopus Shells Found in Ocean Sediments
The key evidence underlying this discovery comes from ancient octopus shells dredged from the seafloor near Antarctica. These shells date back to the last interglacial period 129,000 years ago, a time when global temperatures were similar to or slightly higher than today.
By sequencing DNA preserved within the shells, an international team led by NERC Fellow Dr. Louise Sime from the British Antarctic Survey obtained genetic data from the ancient octopuses that once inhabited the surrounding waters. This allowed them to reconstruct the octopuses’ evolutionary relationships and population size over time.
DNA Reveals Boom and Bust Cycles
The octopus DNA showed pronounced “boom and bust” cycles in population sizes. This matched model simulations of how octopus populations would fare under scenarios of retreating and advancing ice sheets.
During times when the West Antarctic Ice Sheet was stable and intact, food sources were more scarce, and octopus populations stayed small. In contrast, when the ice sheet collapsed, nutrient-rich water surged into the surrounding ocean, fueling an explosion of phytoplankton. This stimulated a bloom in krill and fish populations further up the food chain, allowing the octopuses to thrive.
By aligning the peaks and crashes in ancient octopus numbers with evidence of advancing and retreating ice sheets from ocean sediment cores, Dr. Sime’s team confirmed that a massive collapse event took place during the last interglacial period.
West Antarctic Ice Sheet Retreated 400 Miles Inland
At its maximum extent during the last ice age, the enormous West Antarctic Ice Sheet stretched out to the continental shelf. But 129,000 years ago, rising sea levels caused the grounding line – where the ice sheet starts to float and becomes vulnerable to rapid break up – to retreat backwards by 400 miles. This triggered a massive collapse leading to a 3-4 meter rise in global sea levels.
|West Antarctic Ice Sheet Extent
|Global Sea Levels
|Last Glacial Maximum 20,000 years ago
|Extended out to continental shelf
|Over 120 meters lower than present
|129,000 years ago
|Retreated 400 miles inland
|Over 3 meters higher than present
|Between the LGM and 129,000 years ago extents
Today, scientists fear history could repeat itself, as rising air and ocean temperatures driven by climate change have already caused the West Antarctic Ice Sheet to start retreating in recent decades. This discovery confirms that the ice sheet is prone to catastrophic collapse – and implications for the future are alarming.
Grave Warning for Future Sea Level Rise
The West Antarctic Ice Sheet contains enough ice to raise global sea levels by around 5 meters if it were to completely disintegrate. Since the Industrial Revolution, the planet has already warmed by 1.1°C, causing ice loss from both Antarctica and Greenland to accelerate six-fold.
If warming can breach the stability threshold for ice sheets once again, it could set off irreversible retreat leading to rapid sea level rise within the next few centuries. This would inundate coastal settlements across the world, unless greenhouse gas emissions can be brought under control.
Professor Nerilie Abram from The Australian National University gave this sobering perspective:
“This isn’t just a problem for the future – those impacts may already be locked in. Finding this fingerprint of abrupt sea level rise from Antarctica during warmer times in the past tells us we need to prepare now for what could happen in our near future.”
To mitigate risks of catastrophic sea level rise, the authors stress the critical importance of limiting global warming to the Paris Agreement target of 1.5°C or lower compared to pre-industrial levels. Meeting this goal requires immediately halting further expansion of fossil fuel infrastructure, and aggressively phasing out emissions.
Ongoing Research Efforts
Further research voyages are planned to recover more octopus DNA from ocean sediments around Antarctica, which will reveal even greater insights into the history of the polar ice sheets. These genomic records encoding the memoirs of ice sheet collapses past could prove pivotal in securing civilization’s future.
In conclusion, this remarkable study using DNA from long-dead octopuses spells out an ominous fate for the West Antarctic Ice Sheet under climate change. With temperatures today already warmer than during past collapse events, renewed rapid ice retreat could be imminent. This threatens to push sea levels catastrophically higher within centuries, overwhelming humanity’s capacity to adapt. Our window to prevent triggering this calamitous scenario is rapidly closing – the time for urgent climate action is now.
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