For years, scientists have been concerned about the Thwaites, a vast expanse of up to 130 kilometers of Antarctic ice that has been given the fearsome nickname of the 'glacier at the end of the world'. The shelf, which is about the size of Florida, acts as a natural plug that slows sea level rise. But climate change has no mercy on anything.
Some studies indicate that, with the increase in temperature, the glacier loses 50,000 million tons of frozen water each year, contributing 4% to the rise of the oceans. The collapse of Thwaites could cause a rise of more than 70 centimeters, which would be enough to devastate the coasts of the entire planet.
However, the situation could be even worse. As the massive iceberg acts as a natural dam for the surrounding ice in West Antarctica, scientists have estimated that global sea level could ultimately rise by around 3 meters if this glacier were to collapse.
Ice loss accelerated especially starting in the 1970s, but no one knew exactly when it had started. Researchers from the University of Houston point out in an article published in the journal Proceedings of the National Academy of Science (PNAS) that it was around 1940 when a significant thinning and decline began... due to El Niño.
This phenomenon related to the warming of the Pacific appears in cycles, normally between three and eight years, and wreaks havoc with intense rains that mainly affect the coastal region of South America. Furthermore, the warmer this ocean is, the more hurricanes or typhoons it receives, reducing those in the Atlantic.
According to geologist Rachel Clark and her team, the retreat of the glaciers (both Thwaites and Pine Island, responsible for approximately 25% of the continent's melting) was probably initiated by an extreme El Niño weather pattern that warmed the region. western antarctic.
"What is especially important is that this change is neither random nor specific to a glacier," Clark says in a statement. “It is part of a broader context of changing climate. You simply cannot ignore what is happening on this glacier,” he adds.
The El Niño phenomenon "only lasted a couple of years, but the two glaciers are still in significant retreat," says co-author Julia Wellner, principal investigator of the Thwaites Offshore Research (THOR) project in the United States. "Once the system becomes unbalanced, the withdrawal does not stop," she says.
The findings indicate that ice loss in the Amundsen Sea is predominantly controlled by external factors, involving changes in oceanic and atmospheric circulation, rather than by internal glacier dynamics or local changes, such as melting at the bed or the accumulation of snow on the surface.
"Once ice sheet retreat gets underway, it can continue for decades," says marine geologist James Smith of the British Antarctic Survey. "It is possible that the changes we see today on the Thwaites and Pine Island glaciers - and potentially the entire Amundsen Sea Bay - were essentially set in motion in the 1940s," he concludes.
Researchers collected marine sediment cores recovered from the glacier during a trip in early 2019 aboard the icebreaker Nathaniel B. Palmer. They then used the cores to reconstruct the history of the glacier from the early Holocene (about 11,700 years ago) to the present.
CT scans were used to x-ray the sediment and geochronology, or the science of dating Earth materials, was used to conclude that major ice melting began in the 1940s.
The Thwaites plays a vital role in regulating the stability of the West Antarctic Ice Sheet and therefore global sea level rise. "The glacier is important not only for its contribution to sea level rise, but because it acts like a cork in the bottle that retains a wider area of ice behind it. If the Thwaites becomes destabilized, then there is a possibility that all the ice in West Antarctica will be destabilized," experts say.
