Studying cave stalagmites from past glacial periods can help gauge climate change, according to University of Minnesota research.
To record Earth’s climate history in previous glacial periods, researchers from the University's Department of Earth Sciences and the University of Massachusetts analyzed various characteristics of Peruvian stalagmites in caves. In a study published on Feb. 4, the researchers compiled a more complete record of glacial periods as part of an ongoing effort to understand rapid changes in climate.
“The last glacial period is marked by these really rapid, high amplitude swings in climate. It’s not been clear whether those really rapid, high amplitude climate changes were also present in [earlier] glacial periods,” said lead researcher Stephen Burns, a UMass geosciences professor. “One of the very few archives that can give you that kind of information is stalagmites.”
Previously produced records have not been able to show a clear number of climate events prior to the last glacial period, but the team’s research displays rapid shifts in temperature and precipitation during that time. Burns said what drove rapid climate changes is still not entirely known.
“[This is] probably because we don't fully understand even what they look like during all types of past climates, but they are a part of natural climate variability,” Burns said.
Although this research cannot be directly applied to predicting future climate change patterns, Burns said it can be useful in piecing together and creating more accurate geological records to reference as a type of natural climate change.
University isotope geochemist Larry Edwards used stalagmites as indicators of rainfall and temperature change in climate history. He said initial testing produces a basic record that can then be adjusted by comparing multiple layers of stalagmites.
“In the end, you would have a whole set of oxygen isotope analyses, which would basically tell you something about rainfall at the time,” said Edwards.
The stalagmites were excavated throughout the early 2000s, and found to be over 135,000 years old. Since then, researchers have conducted more than a thousand tests of radiometric dating.
“We got a really nice age range, which was pretty much the whole glacial period before last (the penultimate glacial period), and there is not that much data for that timeframe ... anywhere in the world,” Edwards said.
Lisa Welsh, a geologist who helped collect the samples, said it was interesting to find the initial age results and see major differences.
“It’s neat when you go into a cave, you never really know what you’re going to get at all and what the age of the samples are going to be,” Welsh said. The team was surprised to find the samples were much older than their 10,000-years prediction.
Although the stalagmites were only excavated from South America, the researchers used the data to review previous climate change worldwide.
“The whole climate system is pretty closely tied together,” Burns said. “You can't change climate very much in one part of the world without affecting climate everywhere.”