Spain's Glaciers Peaked Earlier than Previously Believed, Study Shows

Spain's glacial maximum occurred around 26,000 years ago, predating the Earth's overall maximum by some 6,000 years, according to a new study demonstrating how regional climate has varied over time.

The report, according to its authors, reveals how local effects of temperature and precipitation brought the glacial maximum to an end earlier than previously believed in at least one region and, in doing so, provides information that could lead to more accurate global climate models.

The study was conducted in central Spain where the size of ancient glaciers is represented in the layout of the region's boulders since ice carried and dropped them at the margin. For this reason, a ring of boulders indicates the former edge of a glacier that has long since disappeared.

Using a technique known as cosmogenic nuclide exposure dating, the researchers determined the age of the boulders so as to decipher when the region's glaciers reached their greatest extent.

More difficult was determining what caused the glaciers to grow. To unravel this mystery, the international team of researchers turned to caves where stalagmites and stalactites have long kept a record of precipitation given that they grow as a result of dripping water. Here, the scientists used standard radiometric techniques to date the stony formations and, in doing so, gained a look into any precipitation fluxes during the time when glaciers encompassed the area.

"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," Jane Willenbring, a geologist at the University of Pennsylvania and the study's lead researchers, explained in a statement.

As a result, the team discovered that, while the last glacial maximum is believed to have fallen in the range of 19,000 to 23,000 years ago, Spain's occurred more along the lines of 25,000 to 29,000 years ago.

The reason for this, the study's results indicate, is that while temperatures were cool in the range of 19,000 to 23,000 years ago, conditions were relatively dry.

Based on this revision, the researchers determined that the reason for the changes in precipitation were drawn from changes in the intensity of the Sun's radiation on Earth, which is based on the planet's tilt in orbit. Such variations, they explain, can impact wind, temperature and storm patterns.

"That probably means there was a southward shift of the North Atlantic Polar Front, which caused storm tracks to move south, too," Willenbring said. "Also, at this time there was a nice warm source of precipitation, unlike before and after when the ocean was colder."