Octopus DNA Reveals Antarctic Ice Sheet Closer to Collapse
Scientists studying octopus DNA in Antarctica have found evidence that the West Antarctic Ice Sheet (WAIS) is closer to collapse than previously thought, which could lead to significant sea level rise.
Octopus DNA Provides Insight into Antarctic Ice Sheet Retreat
Scientists investigating the retreat of Antarctica's ice sheets have turned to an innovative approach: studying the DNA of octopuses that live in its waters. A new analysis published in Science suggests that geographically-isolated populations of octopuses mated freely around 125,000 years ago, indicating an ice-free corridor during a period when global temperatures were similar to today.
The findings of the study suggest that the West Antarctic Ice Sheet (WAIS) is in a more precarious state than previously believed. If global temperatures continue to rise beyond the Paris Agreement target of 1.5 degrees Celsius, the WAIS could collapse, leading to long-term sea level rise of 3.3 to 5 meters.
Lead author Sally Lau explains that as an evolutionary biologist, she understands how DNA and biology can serve as proxies for changes to Antarctica in the past. By studying the DNA of Turquet's octopus, Lau and her colleagues were able to provide insights into the collapse of the WAIS.
Evidence of Trans-West Antarctic Seaways
To study the genetic history of octopuses and the ice sheet, the researchers sequenced the DNA of 96 samples collected inadvertently as fishing bycatch over the course of 33 years. By analyzing the genomes, they found evidence of trans-West Antarctic seaways that connected different seas around 125,000 years ago.
The genetic mixing indicated that the WAIS collapsed at two separate points in the past. The first collapse occurred around 3-3.5 million years ago during the mid-Pliocene. The second collapse happened during the Last Interglacial period, from 129,000 to 116,000 years ago, which was the last time the planet experienced a temperature increase of 1.5 degrees Celsius compared to pre-industrial levels.
The study provides empirical evidence that the WAIS collapsed in the past when global mean temperatures were similar to current levels. This suggests that the tipping point for future collapse of the WAIS is close, reinforcing the urgent need to address climate change.
Implications for Sea Level Rise and Unanswered Questions
The potential collapse of the WAIS has significant implications for sea level rise. If the ice sheet were to collapse completely, it could lead to a sea level rise of 3.3 meters, which would submerge low-lying coastal areas worldwide.
While the study provides valuable insights, there are still unanswered questions. It remains unclear whether rising temperatures alone caused the past ice sheet collapse or if other factors, such as changing ocean currents and interactions between ice and the solid Earth, played a role. Additionally, it is uncertain whether the sea level rise from a collapsed WAIS would occur gradually over millennia or in more rapid jumps.
Despite these uncertainties, the study underscores the urgency of taking action against climate change. The researchers describe the evidence from octopus DNA as another card added to an already unstable house of cards, emphasizing the need to address climate change before it's too late.
