Heavy thunderstorms in the southern Great Plains of the United States are among the strongest on Earth. In recent years, these storms have increased in frequency and intensity, and new research shows that these changes are linked to climate variability.
Co-authored by Christopher Maupin, Courtney Schumacher and Brendan Roark, all scientists from Texas A&M University’s College of Geosciences, along with other researchers, the results were recently published in Natural geosciences.
In the study, the researchers analyzed the oxygen isotopes of 30,000-50,000-year-old stalactites from Texas caves to understand the trends of past thunderstorms and their durations, using a radar calibration for the isotopes of the storms. precipitation in the region. They found that when storm regimes shift from weakly to strongly organized over millennial time scales, they coincide with well-known global abrupt climate changes during the last ice age, which occurred about 120,000 ago. at 11,500 years.
Through modern synoptic analysis, researchers have learned that thunderstorms in the southern Great Plains are strongly related to changes in wind and humidity regimes occurring on a much larger scale. Understanding these changes and various correlations will not only help reconstruct past thunderstorm occurrences, but will also help predict future mid-latitude thunderstorm patterns.
“Proxy recordings are available on the southern great plains in the caves,” Maupin said. “There are probably thousands of caves in the southern Great Plains and southern Texas. Why hasn’t there been more research in these areas? Cave deposits hold so much promise as a proxy. “
Schumacher said scientists understand modern precipitation patterns and that large storms can deplete isotopes.
“However, we don’t know what will happen in the future, and this work will help predict storm trends in the future,” she said. “If we can run a climate model for the past that is consistent with the cave records, and run that same model in the future, we can have more confidence in its conclusions if it matches the cave records than if they do not. On two models, if one really matches the isotopes of the cave, you can trust that one to understand the distribution of storms in the future. “
Caves hold little-known climatic records
Maupin, a paleoclimatologist, described the limitations that exist in capturing the true distribution of weather events over time.
“There are some really important questions about what has happened in the past regarding the large weather events we experience through mesoscale convective systems (large storms) versus non-mesoscale things (small storms),” he said. declared Maupin. “We get so much precipitation from really big storms, and the model grids can’t capture big weather events because the grids themselves are so big. Paleoclimatology helps organize past events to develop an indirect record of how they react to average climate. “
Maupin collaborated with National Taiwan University to do a uranium and thorium dating and found that the stalactites and stalagmites actually dated from the Ice Age.
Schumacher’s expertise was needed to make connections with various rainy events that occurred over time. She had experience with radar data and global rainfall measurements.
“Large storms that cover hundreds of miles provide about 50 to 80 percent of rain in Texas,” Schumacher said. “These storms today have different isotopic signatures. “
Maupin’s research pushes back on outdated paleo-world principles, as you need to study how storms grow bigger and what influences them, he said.
“These thunderstorms are so big that even though most of the rain occurs in Oklahoma, the rain in Texas will still carry the isotopic signature of these huge storms,” said Maupin. “You fingerprint these systems no matter where they occur, and they don’t need to be super localized to be recognized. Big storms cause depleted isotope signatures. You can’t explain the variability of stalactites. with the only temperature changes. “
Research Experience for Aggie Undergraduates
Celia Lorraine McChesney ’16 and Audrey Housson ’16 were two undergraduate researchers involved in this publication, and both learned a lot through fieldwork, collaboration and the high impact learning experience.
“The cave samples have been used as a high-impact learning tool to understand the paleoclimate of Texas,” said Maupin. “One of the undergraduates started micro-milling the stalactites. I was very fortunate to have access to the resources of the College of Geosciences and to work with these talented undergraduates on groundbreaking research. “
McChesney said his experience working on his graduation thesis at the lab was “invaluable” and the research has allowed him to travel and go into the field.
“As an undergraduate research student at Texas A&M, I was proud to be part of one of the first teams to correlate climate change and weather links in a paleoclimatic dossier,” said Housson. “All this experience allowed me to discover the academic world and made me more confident as a scientist. Now, as a geologist and civil engineer, I work on heavy civil infrastructure projects like tunnels and dams related to water resources. I love how my career ties into my undergraduate research where knowing the correlation between climate change and weather helps plan water resources in the future. “
Funding for this research was provided in part by a High Impact Undergraduate Research Grant from Texas A&M University.