14 DAY TRIAL // In a finding that may force experts to reconsider how ice sheets are influenced by climate change, a group of scientists has determined that the global sea levels were higher than today more than 80,000 years ago. The measurements that led to the new conclusions were collected from Mediterranean caves that were flooded during these events, and that kept a record of what happened in mineral deposits. The actual sea level appears to have been a lot more elevated than anyone anticipated, Nature News reports.
Sea levels are also used as a clear indicator of the state of the planet's ice sheets at any given point. When the Earth is warmer, more ice melts, and water levels increase. Conversely, the opposite holds true during periods of glacial maximum, when records show that the water can reach levels up to 130 meters lower than they have today. The new investigation, conducted by researchers at the University of Iowa in Iowa City, showed that, more than 81,000 years ago, sea levels suddenly increased until they were about one meter higher than today.
This finding conflicts with previous models, which state that ice sheets around the world continuously grew and thickened between 125,000 and 20,000 years ago, when they reached a maximum. Naturally, there was also considerable variation along the way, but this discovery points at the fact that the periodical differences might have been more significant than estimated.
“At face value this is a very beautiful and solid piece of work. It suggests that, for reasons unknown, the sea level which at the time should have been down some 15 meters instead went up one meter, and then went right back down again within just a couple of thousand years,” Columbia University Lamont-Doherty Earth Observatory geologist and climate scientist Wallace Broecker says. The work was conducted by UI geologist Jeffrey Dorale.
The finding also implies that ice sheets are capable of receding considerably over very short periods of time, before resuming their growth at an accelerated pace. But exactly what caused the rise in sea levels some 81,000 years ago is still a mystery to researchers. “It could all come down to an anomaly, caused by some complex feedbacks perhaps related to the global carbon cycle. But we really don't know,” Dorale explains. He adds that the work was conducted in coastal caves on the Spanish island of Mallorca, which were flooded as sea levels in the Mediterranean increased.