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| Stream in Hilo. Photo Credit: Pascal Debrunner |
Scientific Frontline: Extended "At a Glance" Summary: El Niño Flavors and Past Climate Variability
The Core Concept: An analysis of El Niño "flavors"—characterized by distinct peak warming locations in the eastern, central, and coastal Pacific—over the Holocene epoch to understand past climate variability and project future responses.
Key Distinction/Mechanism: Differentiates between eastern Pacific, central Pacific, and coastal El Niño events, noting how each location drives different hydroclimate impacts, frequencies, and regional teleconnection strengths.
Origin/History: Grounded in paleoclimate records spanning the past 12,000 years, utilizing new climate model simulations and proxy indicators developed and analyzed by researchers at the University of Hawaiʻi at Mānoa and the University of Colorado Boulder in 2022.
Major Frameworks/Components:
- Climate model simulations tracking shifts in El Niño flavor frequencies across the Holocene epoch.
- Proxy indicators from coral skeletons, Peruvian mollusk shells, and tropical Andean lake sediments.
- Evaluation of historical frequency trends showing increased Eastern Pacific events alongside decreased Central Pacific and coastal events.
Branch of Science: Atmospheric Sciences, Climatology, Oceanography, Earth Science.
Future Application: Refining global climate models, reducing projection uncertainties, and improving regional water resource management and hazard preparedness for extreme weather events.
Why It Matters: Reconciles conflicting historical proxy records, deepens the understanding of El Niño dynamics, and provides essential insights for anticipating regional climate hazards and global responses to ongoing warming.
As with many natural phenomena, scientists look to the climate of the past to understand what may lie ahead as Earth warms. By assessing so-called ‘flavors’ of El Niño events in historical records and model simulations, researchers have a clearer picture of El Niño patterns over the past 12,000 years and are able to more accurately project future changes and impacts of this powerful force. The study, by scientists at the University of Hawaiʻi at Mānoa and University of Colorado Boulder, was published in Nature Communications.
The new set of climate model simulations developed and analyzed by Christina Karamperidou, lead author of the study and associate professor at UH Mānoa, and co-author Pedro DiNezio, associate professor at the University of Colorado Boulder, are the first to allow the study of changes in the frequency of El Niño flavors during the past 12,000 years.
This work offers new knowledge on how El Niño may respond to climate change and thus can help reduce these uncertainties in global climate models and offer more accurate predictions of El Niño impacts.
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| El Niño flavors; Warm sea surface location: Eastern, Central or coastal. Image Credit: Karamperidou, DiNezio 2022) |
“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 Karamperidou, associate professor of atmospheric sciences at the UH Mānoa School of Ocean and Earth Science and Technology. “Doing this allowed us to reconcile conflicting records of past El Niño behavior.”
El Niño is the primary factor affecting variability in water temperature and trade wind strength in the Pacific. Typically, researchers look for indicators of El Niño events in ancient, preserved material such as coral skeletons, Peruvian mollusk shells or lake sediment from the tropical Andes because locked within are indicators of past temperature and rainfall across Pacific.
“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 enabled the researchers to test a hypothesis that Karamperidou and colleagues posed in 2015—that paleoclimate records across the Pacific could be explained by changes in El Niño flavors.
“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.”
Connections to Hawaiʻi’s rainfall, hazards
El Niño events have significant impacts on Hawaiʻi’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 Hawaiʻi 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.”
Surprising impacts
Additionally, this is the first study into the response of coastal El Niño events to climate changes. During these events the sea surface warming is confined off the coast of South America while the conditions in the rest of the Pacific basin are normal or colder than normal.
“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.”
Reference material: What Is: El Niño, La Niña, and a Climate in Flux
Published in journal: Nature Communications
Title: Holocene hydroclimatic variability in the tropical Pacific explained by changing ENSO diversity
Authors: Christina Karamperidou, and Pedro N. DiNezio
Source/Credit: University of Hawaiʻi
Edited by: Scientific Frontline
Reference Number: en121222_01