Scientists studying the history of sea levels in Spain say they've found evidence that glaciers can form and melt faster than previously thought.
The research done in caves on the Spanish island of Majorca suggests that the sea level 81,000 years ago was more than a metre higher than it is today.
The sea level rises when glaciers melt and falls when glaciers form. Between the last warm interval, 125,000 years ago, and the last ice age, 20,000 years ago, the sea fell by about 130 metres.
The falling of the sea level wasn't steady, though, and may have gone up and down in wide swings during that time, even as the overall trend was downward.
This finding that the sea level was higher 81,000 years ago than it is now suggests global temperatures were at least as high as they are now, if not higher, even though the level of carbon dioxide in the atmosphere was lower then.
Jeffrey Dorale and colleagues took measurements of geological formations in the cave, which has been intermittently submerged by the Mediterranean Sea over the last hundreds of thousands of years.
The stalactites on the roofs of the Vallgomera Cave on the island become encrusted with deposited minerals, called speleothem encrustations, as the sea level falls, leaving a record that geologists can read.
To date the mineral formations, the researchers matched different forms, or isotopes, of oxygen in the encrustations to established data, called marine isotope stages, from deep-sea core samples.
The results, published this week in the journal Science, are at odds with conventional thinking on how fast ice sheets can form and recede.
If the results are verified, they could change the way geologists think about the way ice ages come and go.