Today’s Intensifying Thunderstorms Replicate an Ancient Pattern that Dates Back at Least 50,000 Years
While thunderous sky and stunning displays of air-splitting light can be an exciting sight to see, thunderstorms can also cause a great deal of harm.
From igniting major wildfires to generating flash flooding, damaging hail, and even tornadoes, this wild weather has the potential to ruin homes and businesses while also claiming lives.
Thunderstorms that rage through the Southern Great Plains of the United States are among the most powerful on the planet. These storm complexes, dubbed mesoscale convective systems, account for up to 90% of the region’s yearly rainfall.
Their intensity and frequency have increased, but even the most sophisticated climate models struggle to anticipate how and when they will occur.
To aid in the refinement of climate models for the Southern Great Plains, paleoclimatologist Christopher Maupin of Texas A&M University and colleagues measured the strength of past storms using oxygen and hydrogen isotopes.
Water molecules derived from elements with an extra neutron or two take somewhat more energy to evaporate and release slightly more energy during condensation. This puts a distinct imprint on the isotope ratios separated by rainfall under varied situations.
By comparing the results of modern analyses to historic ratios of hydrogen and oxygen isotopes trapped in stalactites in Texan caverns, the researchers were able to create an accurate picture of historical weather occurrences.
“These thunderstorms are so big that even if most of the rain occurs in Oklahoma, rain in Texas will still carry isotopic signature of these huge storms,” Maupin explained.
“You are fingerprinting these systems regardless of their location, and they do not need to be extremely localized in order to be recognized. Large storms produce isotope fingerprints that are depleted.”
Using a different set of isotopes, this time uranium and thorium, the scientists determined the age of the stalactites and stalagmites to be between 30 and 50 thousand years old.
Measuring oxygen and hydrogen isotope alterations down to their atomic lengths enabled the researchers to observe how storms cycled from poorly structured to highly organized around every thousand years. The more organized a storm complex grows, the more severe and destructive it becomes.
They discovered that these fluctuations in thunderstorm intensity corresponded to well-documented, rapid changes in global climate, dubbed Dansgaard–Oeschger events.
Additionally, the researchers discovered that these increases in intensity coincide with a decrease in rainfall in the southern United States and increased atmospheric upwelling in the Santa Barbara Basin area.
They believe the observed trend indicates that a rise in the frequency or severity of the massive global air waves that drive the weather, known as Rossby waves, may be providing the additional lift required to power these larger storms.
“Modern anthropogenic climate forcing has increasingly favored an amplification of these synoptic factors,” the researchers concluded in their article.
“This work will help predict trends of storms in the future,” geoscientist Courtney Schumacher remarked.
“If we can run a climate model in the past that is compatible with cave records and then run it in the future, we can have higher confidence in its findings if they match the cave records. If one of the two models accurately reproduces the cave isotopes, then it can be trusted to predict storm distribution in the future.”
These discoveries may also have practical implications, according to Audrey Housson, a geologist and civil engineer who contributed to the project as an undergraduate:
Understanding the relationship between climate change and weather can help us plan for critical infrastructure, such as water resources, in the future.
This study was published in the journal Nature Geoscience.