Glaciers Peaked in Spain Far Sooner: The Real Glacial Maximum

About 20,000 years ago, glaciers covered most of our planet. The icy climate played home to species that are now largely extinct and sea levels were far lower than they are today. Now, scientists have discovered that this glacial maximum may occurred far earlier in parts of southern Europe. It turns out that in Spain, this maximum took place about 26,000 years ago.

It's perhaps not surprising that local climates experienced varying conditions. Even today there are sections of our world that are experiencing either warmer or colder conditions, despite the fact that our world is warming overall.  In this latest study, though, the researchers wanted to unravel the mystery as to why and when glaciers grow and shrink.

It's difficult to find out what causes glaciers to transform. While studying the boulders that rim ancient glaciers tell a little bit about them, they can't distinguish specific conditions, such as moisture and cold temperature. In order to determine these two factors, the scientists looked to caves. Stalagmites and stalactites carry a precipitation record since they grow as a result of dripping water.

"If you add the cave data to the data from the glaciers, it gives you a neat way of figuring out whether it was cold temperatures or higher precipitation that drove the glacier growth at the time," said Jane Willenbring, one of the researchers, in a news release.

In order to find out the age of the boulders strewn by the glaciers, the scientists used a method called cosmogenic nuclide exposure dating. This technique measures the chemical residue of supernova explosions. They also used standard radiometric techniques to date the stalagmites found in the nearby Eagle Cave.

In the end, the researchers found that the last glacial maximum occurred somewhere between 25,000 and 29,000 years ago in Spain. Although temperatures were cool in the range of 19,000 to 23,000 years ago, the conditions were also dry. This means that the glaciers did not regain the size they had several thousand years earlier.

The findings reveal a little bit more about the climate thousands of years ago. This, in turn, will help provide more context for creating accurate global climate models. This will allow scientists to better calculate what might happen in the future.

The findings are published in the journal Scientific Reports.