The mineral crusts on high-and-dry formations in coastal caves of Majorca indicate that during the latest ice age, sea level briefly and inexplicably rose more than one meter higher than today’s level. Cave formations along the coast of an island in the Mediterranean Sea hold evidence that sea level can rise and fall abruptly during an ice age, a finding that casts some doubt on current notions about how those lengthy cold spells develop and progress.
At the height of an ice age, immense volumes of water are locked up in land-based ice sheets, and ocean levels can be as much as 130 meters below where they are today. By contrast, when that ice melts during warm periods, sea level can be a few meters higher than the modern-day standard, says Jeffrey Dorale, a paleoclimatologist at the University of Iowa in Iowa City. Now, Dorale and his colleagues report in the Feb. 12 Science that during a brief interval well within the most recent ice age, sea level suddenly and inexplicably rose to a height more than one meter above today’s.
Studies at a handful of sites worldwide have noted that sea level reached an exceedingly brief and similarly enigmatic high point around 81,000 years ago, says Dorale. Those results have been controversial and, for the most part, have been “politely ignored because they don’t fit the presumed pattern” of how ice ages develop and progress, he says.
Scientists have long noted erratic dips and jumps in sea level during Earth’s ice ages, but debate has typically focused on the magnitude of those swings, says Dorale. The new findings are somewhat disturbing because they suggest that at some points during an ice age, sea level can rise as much as 2 meters over the course of a century. “It’s tough to explain how to melt that much ice that fast,” he admits.