19 Feb (GEOL) Rob Domeyko, Paleoclimatology

Speaker: Robert A. Domeyko, Postdoctoral Fellow, University of Texas Institute for Geophysics

Time: Thu, 19 Feb, 4:30pm ET

Location: Exploratory 1309 and via Zoom (for link, email lhinnov@gmu.edu)

Title: Rare coral archives confirm weaker El Niño during colder, abrupt climate regimes

Host: Linda Hinnov

Abstract: Extreme El Niño events – the warm phase of the El Niño–Southern Oscillation (ENSO) – have increased in frequency since the late 20th century, raising concern about how ENSO responds to changes in Earth’s climate system. Climate model simulations suggest that El Niño activity weakens during colder climates and intensifies under anthropogenic warming, yet direct geological evidence from past cold climate intervals remains sparse due to the limited availability of suitable paleoarchives. In this talk, I present new oxygen isotope records from fossil corals recovered from Vanuatu that capture key intervals of the last deglaciation. I combine these records with climate model simulations to evaluate changes in ENSO variance and extreme El Niño frequency during cold, abrupt climate events. The coral records constrain total interannual climate variance at ENSO timescales, while a complementary analysis of model output isolates the portion of that variance associated with ENSO across the tropical Pacific. Both the coral data and model results indicate reduced interannual variance and fewer extreme El Niño events between ~12 and 15 thousand years ago, coincident with the Younger Dryas and Heinrich Stadial 1 abrupt climate events. Model simulations further reveal distinct climate regimes, linking weaker ENSO activity during cold deglacial conditions to stronger variance and more frequent extremes in warmer climates, including under CO₂ doubling scenarios. Together, these results place recent El Niño changes in a longer geological context and suggest that anthropogenic forcing fundamentally alters ENSO behavior, amplifying the impacts of extreme El Niño events across the tropical Pacific and beyond.

Bio: Robert A. Domeyko received his Ph.D. in Geological Sciences from The University of Texas at Austin in 2025. His research focuses on past climate variability, particularly El Niño behavior, using coral geochemical records and climate model simulations to understand how large scale climate change influences tropical climate extremes.