Traditionally, climate scientists have relied on ice cores collected from Antarctica and Greenland to create a record of Earth’s climate history. This is largely because these areas are covered by incredibly thick layers of ice, which allows scientists to extract large, uninterrupted cores that can measure up to several kilometres in length.

In contrast, finding land-based environmental archives in hot, arid areas like the southwestern United States, is particularly difficult. That said, a team of researchers led by Oregon State University’s Kathleen Wendt have just managed to piece together 580,000 years of climate history from a calcite deposit found in Devils Hole cave in southern Nevada.

The results, published last week in the journal Nature Communications, offer a rare insight into how the climate in this dry corner of the US has changed over the past half a million years.

“What we see over this time span are glacial periods, when Nevada was cooler and wetter, followed by interglacial periods, when Nevada was hot and dry, like what we’re experiencing today,” explained Wendt in a recent statement. “But midway through those interglacial periods, the available groundwater dropped sharply and vegetation plummeted.”

Nevada was home to many iconic species of megafauna during these cooler glacial periods, including mammoths, bison, ground sloths, dire wolves and sabre-toothed cats. As periods shifted from glacials to interglacials, some of these cold-adapted species would have suffered and may have been pushed further north where conditions remained more favourable.

Prior to this recent study, Devils Hole had already been identified as a great place to find such climate records, thanks to the fact groundwater has flowed through it for hundreds of thousands of years and plastered its walls with metre-thick layers of minerals, such as calcite.

To extract a core from the calcite deposit, Wendt and her team abseiled 20m down a narrow shaft and squeezed through a tight opening to reach the deepest part of Devils Hole II – a second, much deeper chamber of the Devils Hole system that’s shaped more like a fissure than a traditional cave.

After reaching the deposit they drilled a one-metre-long core and sent it back up to the surface to undergo oxygen isotope analysis. The oxygen isotopes trapped inside the calcite vary depending on the climate at the time, allowing scientists to reconstruct the region’s climate history. 

The team also learned about rainfall in the region. Christo Buizert, also from Oregon State University and a co-author of the recent study, explained how knowledge of past climates can inform our understanding of current and future climates.

“Today, the bulk of the rainstorms coming off the ocean hit the Pacific Northwest, but during ice age periods, that same belt of rainstorms would land a lot further south,” he said. “That tells us these storm systems can move up and down the coast, and they can shift quickly and dramatically. This raises questions about what we might expect in this region in the future as climate continues to change.”

Top image: Devils Hole cave descent. Credit: Robbie Shone

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