WVU researcher explores ancient tree rings to predict future space weather
"If one of these events were to happen today and you were on a high latitude flight flying to Norway, you'd probably receive your lifetime dose of radiation on the plane," Hessl said. "And if you were in space, it potentially could kill you."
Hessl has been awarded more than $202,000 from the National Science Foundation to study these phenomena further. The project focuses on tree rings' role in documenting past solar activity, particularly events known as "Miyake events." These rare storms, first discovered in tree rings from 774 AD and 993 AD, are marked by sudden spikes in atmospheric radiocarbon levels. Since their discovery 12 years ago, seven more such events have been identified over the past 14,000 years.
"Some of these events were really extreme and would be incredibly disruptive to our telecommunications system now," Hessl said. "It's a very rare event, but it's not out of the question. We're dependent on satellites and, if it did happen again, it would probably wipe out most of our telecommunications, taking 15 years to recover. It's that powerful."
Solar flares are the primary cause of these solar energetic particle events, though galactic cosmic rays from supernovas could also contribute. By analyzing tree ring records from around the globe, Hessl aims to better understand the origins and impacts of these events. However, she cautioned that interpreting tree ring data is more complex than previously thought.
"Until recently, scientists have assumed that trees take up radiocarbon evenly," Hessl said. "We've been treating trees as if they're scientific instruments. But they're not. They're potentially very biased in the way they take up the radiocarbon."
Some trees may store carbon for later use, complicating the process of determining how reliably they record atmospheric changes. Hessl's team, including Maria Carbone from Northern Arizona University and Rachael Filwett from Montana State University, is studying tree species from different regions of the U.S., each affected by a past Miyake event. They hope to understand how tree species with varying growth strategies capture atmospheric radiocarbon.
"We're looking at three species that have very different physiological strategies for wood production," Hessl said. "An evergreen conifer from Utah, the bristlecone pine, is the longest-lived tree species in the world. They live for several thousand years and they're the backbone of what we know about past radiocarbon in the atmosphere."
The research will compare bristlecone pines in Utah with bald cypress trees from North Carolina and oak trees preserved in Missouri riverbeds. Using cross dating techniques, the team will analyze tree rings from these species to investigate how each recorded the atmospheric conditions of past Miyake events.
"We're trying to define how extreme those events were," Hessl said. "When did they occur, exactly? How long did the radiocarbon last in the atmosphere? We need to be sure we're using reliable recorders, so that's what we're trying to figure out. How reliable are these trees at recording radiocarbon levels in the atmosphere, really?"
Hessl's research could offer critical insights into how we prepare for future space weather, particularly extreme events that could disrupt modern technology. She emphasized the importance of proactive measures, even if such events remain rare.
"Some stuff gets a little overblown, but we saw what happened during the pandemic in terms of initial panic. So it's very reasonable to try and figure out what the upper end bookmark of these things are, and then communicate that to the IT community so our technologies can be protected."