Climate variability

More intense and more frequent thunderstorms linked to global climate variability

The large thunderstorms in the Great Plains of the southern 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 at Texas A&M University’s College of Geosciences, along with other researchers, the findings were recently published in Nature geoscience.

In the study, researchers analyzed oxygen isotopes of 30,000-50,000-year-old stalactites from Texas caves to understand patterns of past thunderstorms and their durations, using radar calibration for precipitation isotopes. of the region. They found that when storm patterns shift from weakly to strongly organized on millennial timescales, they coincide with well-known abrupt climate changes during the last ice age, which occurred around 120,000 years ago. at 11,500 years old.

Through modern synoptic analysis, researchers have learned that thunderstorms in the Southern Great Plains are strongly linked to changes in wind and humidity patterns 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 in the southern Great Plains in caves,” Maupin said. “There are probably thousands of caves in the southern Great Plains and southern Texas. Why hasn’t more research been done in these areas? The cave deposits hold so much promise as proxies.”

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 future storm trends,” 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 results if it matched the cave records compared to see if they didn’t. Out of two models, if one really matches the cave isotopes, you can trust it to understand the distribution of storms in the future.”

The 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 really important questions about what happened in the past regarding the large weather events that we encounter through mesoscale convective systems (large storms) versus non-mesoscale things (small storms),” said said Maupin. “We get so much precipitation from really big storms, and 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 the how they react to the average climate.”

Maupin collaborated with National Taiwan University to do uranium and thorium dating and discovered that the stalactites and stalagmites were actually from the Ice Age.

Interdisciplinary collaboration

Schumacher’s expertise was needed to make connections to various rain events that occurred over time. She had experience working with radar data and global rainfall measurements.

“Big storms that cover hundreds of miles provide about 50 to 80 percent of the rainfall in Texas,” Schumacher said. “Nowadays, these storms have different isotopic signatures.”

Maupin’s research pushes outdated principles in the paleoworld, because one needs to study how storms grow 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,” Maupin said. “You fingerprint these systems wherever they happen, and they don’t have to be super localized to be recognized. Big storms cause depleted isotopic signatures. You can’t explain the variability of stalactites with temperature changes alone.”

Aggie Undergraduate Student Research Experience

Celia Lorraine McChesney ’16 and Audrey Housson ’16 were two undergraduate researchers involved in this publication, and both learned a great deal through fieldwork, collaboration, and the high-impact learning experience.

“The samples from the caves were used as a high-impact learning tool to understand the paleoclimate of Texas,” Maupin said. “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 her experience working on her senior thesis in the lab was “invaluable” and the research allowed her to travel and go into the field.

“As a research undergraduate 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 paleoclimate record,” Housson said. “All of this experience introduced me to academia 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 is linked to my undergraduate research where knowledge of the correlation between climate change and weather helps plan water resources in the future.”

Funding for this research was provided in part by a Texas A&M University High Impact Undergraduate Research Fellowship.