This octopus’ DNA provides clues to the recent collapse of the Antarctic ice sheet

In the sea around Antarctica, small cephalopods are called Turquet squids They have been crawling along the ocean floor for around four million years. These animals, approximately 15 centimeters long (tentacles excluded), can go quite unnoticed. But a study published in Science points out that the DNA of these animals can help determine when the West Antarctic Ice Sheet (WAIS) last collapsed.

The complete collapse of the WAIS would have devastating consequences and could lead to a rise in global mean sea level of 3 to 5 meters.

In recent years the global warming of the oceans – caused by greenhouse gas emissions from burning fossil fuels – has put the ice sheet in an increasingly precarious position. According to a model study published in Nature climate changeEven in the best of times, melting is inevitable. But a better knowledge of its past could help us understand what’s to come.

By understanding how the West Antarctic Ice Sheet (WAIS) was constructed in the recent past, when temperatures were similar to today, we can improve sea level rise projections.

Jan Strugnell (James Cook University, Australia)

“What makes WAIS important is that it is also currently Antarctica’s largest contributor to global sea level rise,” he says. Jan StrugnellDirector of the Center for Sustainable Tropical Fisheries and Aquaculture at James Cook University in Australia and leader of the now published study Science.

According to Strugnell, “Understanding how the WAIS was configured in the recent past, when global temperatures were similar to today, will help us improve future projections of sea level rise.”

Genetic analysis of 96 octopuses from both seas

The team turned to Turquet’s octopus (Pareledone turqueti) Looking for answers. Although these animals live in the waters throughout the frozen continent, their populations in the Ross Sea and Weddell Sea are separated by the impassable WAIS and they rarely stray far from their habitat. If researchers could determine how long the two populations interbred, it could provide some clues as to when the ice sheet last melted.

In the study scientists They sequenced the DNA of 96 turquet squid from across the continent, accidentally caught by fishermen or preserved in museum collections. Although the oldest specimen dates to the 1990s, genetic analysis could provide insight into the octopus family tree millions of years ago.

A harsh warning

A genetic analysis found that octopuses from the Weddell Sea and Ross Sea interbred around 54,000 to 139,000 years ago in a period known as the Last Interglacial.

The genetic analysis found that Weddell and Ross octopuses interbred between about 54,000 and 139,000 years ago, during the last interglacial period, suggesting ice collapse during that time.

Average global temperatures are currently around 1.2 degrees Celsius above the pre-industrial average. During the last interglacial period, the Earth was 0.5 to 1.5 degrees Celsius warmer than the pre-industrial average, but sea levels were 4 to 7 meters higher than today.

Although it is still unclear when WAIS melted and how long it lasted, scientists say the study is a stark warning for the planet.

Reference:

Jan M. Strugnell el al. “Genomic evidence for the collapse of the West Antarctic Ice Sheet during the Last Interglacial.” Science (2023).

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