A large ice sheet in Antarctica, which according to current climate models could disappear due to climate change, managed to survive the last warm interglacial period, over 100,000 years ago.
Scientists from the University of Cambridge and the British Antarctic Survey have used ice core records to draw new conclusions about how Antarctica was affected by the increase in global temperatures back then.
Discoveries about the ice sheet of West Antarctica
The new study, published in the journal Nature, reveals that large portions of the ice sheet of West Antarctica were lost, contributing to a significant rise in sea level. However, the data also indicate that the Ronne ice shelf, which extends over 430,000 square kilometers across the Weddell Sea, survived this period of global warming.
Greenhouse gas emissions are warming the Earth at an unprecedented rate and scale. Although anthropogenic warming has no direct historical parallel, warm episodes in Earth’s history may provide clues about the future.
Temperatures 3 degrees warmer than today
A team of scientists led by Eric Wolff from the University of Cambridge wanted to find out what happened to the ice sheet of West Antarctica during the last interglacial, when polar regions were approximately 3°C warmer than today and sea levels were considerably higher. This period of Earth’s history is considered comparable to the conditions we may experience in a few decades.
This information is crucial for predicting how and when the ice sheet of West Antarctica will change due to future warming.
The ice sheet and its vulnerability
The ice sheet of West Antarctica contains enough freshwater to raise sea levels by 3 to 4 meters. This ice sheet is particularly vulnerable to warming due to its bowl-like shape, which allows seawater to flow under its edge and slowly melt its base.
The Ronne ice shelf extends from the ice sheet to the Atlantic Ocean, forming a floating platform that acts as a buttress holding back and protecting the interior glaciers.
Research at Skytrain Ice Rise
In 2019, Wolff and his team collected a 651-meter-long ice core from Skytrain Ice Rise, a coastal dome near the Ronne ice shelf.
The site is close enough to the ice sheet of Antarctica West to witness its contraction while remaining intact, meaning that data from this site can offer a long-term view of the stability of this vast ice sheet and its contribution to rising sea levels.
Analysis of ice cores
By analyzing the composition of the water isotopes in the ice core, they discovered that the ice sheet of West Antarctica partially reduced during the last interglacial, perhaps decreasing to half of its current mass.
They also measured the marine salt content of the core to estimate the amount of sea spray and, therefore, the proximity of the site to the coast. That dataset showed that the Ronne ice shelf covered a similar area as today.
Implications of the study
Although the ice sheet significantly reduced, this does not represent the catastrophic collapse that some reconstructions had suggested. Lead author Eric Wolff explained: “We are seeing that the ice sheet retreated, but not with the additional disappearance of the Ronne ice shelf.” However, he added: “we still know that sea level was significantly higher at that time.”
Scientists have clear evidence that sea level was several meters higher than today during the last interglacial. The loss of the ice sheet of West Antarctica was thought to be the most likely cause.
New questions and perspectives
Rachael Rhodes, co-author of the Cambridge Earth Sciences study, commented on the new questions raised by the research: “The ice melt that led to the rise in sea level had to come from somewhere, so now we must ask where else it might have come from. It may be necessary to reevaluate whether the ice sheet of East Antarctica was also a significant source of freshwater.”
The researchers claim that their findings will help improve projections of what may happen to the ice sheets as our climate warms. The greatest uncertainty in long-term sea level projections, including those made by the IPCC, is the fate and stability of the ice sheet of West Antarctica.
Do you already know our YouTube channel? Subscribe now!
