In order to comprehend what may lie ahead as the Earth heats, scientists study previous climate, as they do with many other natural phenomena. Researchers have a clearer understanding of El Nio trends over the past 12,000 years and are better able to predict future changes and repercussions of this potent force because to their analysis of so-called “flavors” of El Nio episodes in historical climate data and model simulations.
Scientists from the University of Hawaii at Manoa and the University of Colorado Boulder conducted the study, which was just published in Nature Communications.
“We used a unique set of climate model simulations that span the Holocene, the past 12,000 years, and accounted for changes in the frequency of El Niño flavors, the three preferred locations in which the peak of warming during different El Niño events occur eastern Pacific, central Pacific, and coastal,” said Christina Karamperidou, lead author of the study and associate professor of atmospheric sciences at the UH Manoa School of Ocean and Earth Science and Technology (SOEST). “Doing this allowed us to reconcile conflicting records of past El Niño behavior.”
The main element influencing changes in trade wind speed and water temperature in the Pacific is El Niño. Researchers frequently hunt for signs of El Nio episodes in old, preserved material like coral skeletons, Peruvian snail shells, or lake sediment from the tropical Andes because these materials contain clues to former Pacific temperature and precipitation.
“However, depending on where the samples are taken from eastern Pacific, central Pacific, or near the South American coast the frequency of El Niño events appears to exhibit different patterns,” said Karamperidou. “Records from the eastern Pacific show an intensification of El Niño activity from early to late Holocene, while records from the central Pacific show highly variable El Niño throughout the Holocene.”
This information is important for water resource managers among others to better prepare for Hawai’i regional climate. So, it is imperative that we gain a better understanding of the mechanisms of these flavors, and also improve their representation in climate models and assess their projected changes under future climate conditions.
Christina Karamperidou
The latest set of climate model simulations created by Karamperidou and co-author Pedro DiNezio, an associate professor at the University of Colorado Boulder, are the first to enable the analysis of variations in El Niño frequency over the last 12,000 years.
This gave the researchers the chance to test the idea put forth by Karamperidou and colleagues in 2015 that variations in El Nio tastes could account for paleoclimate records across the Pacific.
“Indeed, we showed that Eastern Pacific events have increased in frequency from early to late Holocene, while Central Pacific and Coastal events have decreased in frequency, resulting in changes in the hydroclimate in the tropical Pacific,” said Karamperidou. “Importantly, we showed that it is not only their frequency but also the strength of their impact that changes, which is important for interpreting records of past climate.”
Surprising impact of coastal El Niño
Additionally, this is the first investigation into how coastal El Nio episodes are affected by climate change. While the rest of the Pacific basin has normal or colder-than-average temperatures during these episodes, the sea surface warming is limited to the South American coast.
“These coastal events have supersized impacts with severe flooding and disasters in countries like Peru and Ecuador,” said Karamperidou. “In fact, we showed in another recent paper that even though these events are not felt around the globe like the more widely known Eastern and Central Pacific events, a better understanding of the mechanisms that drive them is essential for understanding the drivers of the other two flavors, as well.”
Connections to Hawai’i’s rainfall, hazards
El Niño events have significant impacts on Hawai’i’s rainfall, trade wind strength, the probability of hurricane formation and drought, and the type of El Niño event matters for these impacts.
“This information is important for water resource managers among others to better prepare for Hawai’i regional climate,” said Karamperidou. “So, it is imperative that we gain a better understanding of the mechanisms of these flavors, and also improve their representation in climate models and assess their projected changes under future climate conditions.”
This research provides fresh information on how El Niño might adapt to climate change, which might assist lessen the uncertainty in projections of El Niño impacts made by global climate models.
