While it is known that correlations exist between volcanic events and ENSO, the nature and extent of these connections are still disputed among the scientific community due to lack of conclusive evidence. Specifically, there is debate over whether or not the radiative forcing of large volcanic eruptions cause dynamic responses from ENSO.
Volcanic eruptions cause sulfate aerosols to be injected into the stratosphere. This disrupts incoming solar radiation and results in short term cooling. The ocean dynamical thermostat mechanism suggests that this cooling system affects the tropical pacific sea surface temperature (SST) gradient and weakens trade winds. These changes promote El Niño conditions, and the eastern equatorial Pacific warms up to compensate for tropical Pacific cooling. Previous studies implementing both paleoclimate data and coupled general circulation models (GCMs) have suggested that volcanic eruptions might trigger or increase occurrences of El Nino events. However, it has also been suggested that only the large, tropical, explosive eruptions increase the likelihood of or generate an El Niño event, whereas smaller eruptions do not show a significant effect.
This study, funded by COM, uses a newly developed Paleo Hydrodynamics Data Assimilation product (PHYDA) to further analyze the connections between volcanic eruptions and tropical Pacific dynamics. The software includes data from the past 2,000 years. In this study, cross-referencing SST data fields from PHYDA with coincident volcanism events allowed for researchers to test the response of ENSO to large-scale, tropical volcanic events. The results show a weak warming response from El Niño in frequency based analyses, but not when using more common analysis methods.
For more information, contact Virginia Selz.