Abstract
Abstract. Using the Max Planck Institute Grand Ensemble (MPI-GE) with 200 members for the historical simulation (1850–2005), we investigate the impact of the spatial distribution of volcanic aerosols on the El Niño–Southern Oscillation (ENSO) response. In particular, we select three eruptions (El Chichón, Agung and Pinatubo) in which the aerosol is respectively confined to the Northern Hemisphere, the Southern Hemisphere or equally distributed across the Equator. Our results show that relative ENSO anomalies start at the end of the year of the eruption and peak in the following one. We especially found that when the aerosol is located in the Northern Hemisphere or is symmetrically distributed, relative El Niño-like anomalies develop, while aerosol distribution confined to the Southern Hemisphere leads to a relative La Niña-like anomaly. Our results point to the volcanically induced displacement of the Intertropical Convergence Zone (ITCZ) as a key mechanism that drives the ENSO response, while suggesting that the other mechanisms (the ocean dynamical thermostat and the cooling of tropical northern Africa or the Maritime Continent) commonly invoked to explain the post-eruption ENSO response may be less important in our model.
Highlights
Aerosol particles from volcanic eruptions are one of the most important non-anthropogenic radiative forcings that have influenced the climate system in the past centuries (Robock, 2000)
The volcanic eruptions analysed in the present study show three distinct aerosol plumes
Our study used the largest ensemble simulation (200 ensembles) currently available of the historical period performed with the MPI-ESM model to better understand the impact of the volcanic eruptions on El Niño–Southern Oscillation (ENSO)
Summary
Aerosol particles from volcanic eruptions are one of the most important non-anthropogenic radiative forcings that have influenced the climate system in the past centuries (Robock, 2000). Oxidized sulfur gases (mainly in form of SO2) injected into the stratosphere by large Plinian eruptions form sulfate aerosols (H2SO4) (Pinto et al, 1989; Pollack et al, 1976) that have a time residence of 1–3 years (Barnes and Hofmann, 1997; Robock and Liu, 1994). These particles both scatter and absorb incoming solar radiation as well as part of the outgoing longwave radiation (Stenchikov et al, 1998; Timmreck, 2012). These rapid modifications in temperature may induce dynamical changes in the atmosphere and in the ocean, including a strengthening of the polar vortex (e.g. Christiansen, 2008; Driscoll et al, 2012; Kodera, 1994; Stenchikov et al, 2006), a weak-
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