Mallorca caves hold the secret of how high the sea will rise on the planet

The study, conducted by an international team led by the University of South Florida (USF), and featured on the cover of July 1, Science AdvancesTry to find out what sea levels were before the industrial age and find out how much they rose with the effect of modern global warming.

The team of USF graduate students traveled to Mallorca (Balearic Islands), where there are more than 1,000 cave systems, some of which have mineral deposits formed millions of years ago. For this study, they focused on analyzing sediments from 4,000 years ago to the present.

The team found evidence of a previously unknown 20-centimetre sea level rise that occurred almost 3200 years ago, when the polar ice caps naturally melted at a rate of 0.5 millimeters per year for 400 years. Otherwise, sea level remained extremely stable until 1900, despite major climatic events such as the Medieval Warm Period and the Little Ice Age.

More than 4,000 years increase in a century

“The results of our study are alarming”said lead author Bogdan P. Onac, a professor of geology at USF. “Sea level rise since the 1900s is unprecedented compared to the natural change in ice volumes over the last 4,000 years. This means that if global temperatures continue to rise, sea levels may eventually reach higher levels than scientists previously predicted.

To create a timeline, the team collected 13 samples from eight caves on the Mediterranean coast. Note that mineral deposits are somewhat rare: they only form near the shore in cave passages that have been repeatedly flooded by seawater, making them accurate predictors of sea-level changes over time. Each deposit contains valuable information about the past and future, helping researchers determine how quickly sea levels will rise in the coming decades and centuries.

The samples were taken to the University of New Mexico (USA) in Switzerland and the University of Bern, where special instruments were used to determine their age using the uranium series method. Over time, uranium decomposes into other elements such as thorium and lead, allowing researchers to create a documented sea level timeline at each deposit.

Harvard University’s sophisticated software helped generate predictions using various ice models and Earth parameters to show an accurate history of sea level. These estimates are important because they allow researchers to predict past global mean sea level, which is key to addressing future sea level rise.

“If people continue to be the main driving force [del calentamiento] “If the temperature rises by 1.5 degrees in the near future, there will be irreversible damage,” he said. “From then on there will be no turning back.”

Permanent flooding from sea level rise won’t happen overnight, but Onac says it will become more common during storm surges and hurricanes. With almost 40 percent of the world’s population living very close to the coast, sea level rise could be catastrophic with significant social and economic impacts.

“Even if we stop now, sea level will continue to rise for at least a few decades, if not centuries. because the system is warming up,” he explains.

In June, Onac received a new research grant from the National Science Foundation to continue her research to predict future sea level rise due to global warming. This subsidy will allow Onaç extending research beyond history by 130,000 years and promoting a better understanding of sea level globally. Starting in September, Onac and his team will begin analyzing cave beds from around the world, including Italy, Greece, Mexico and Cuba.

This work was conducted in collaboration with scientists from Harvard University, University of New Mexico, University of the Balearic Islands, Roma Tre University, Rutgers University, Australian National University, Los Alamos National Laboratory and the University of Bern.

Full study (in English): https://www.science.org/doi/10.1126/sciadv.abm6185

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