No consistent ENSO response to volcanic forcing over the last millennium
Abstract
The El Niño-Southern Oscillation (ENSO) shapes global climate patterns yet its sensitivity to external climate forcing remains uncertain. Modeling studies suggest that ENSO is sensitive to sulfate aerosol forcing associated with explosive volcanism but observational support for this effect remains ambiguous given the rarity of large volcanic eruptions and the short instrumental record. Here, we use sea surface temperature (SST) reconstructions derived from two data products to gauge ENSO's response to large volcanic eruptions of the last millennium: (1) absolutely dated fossil corals from the central tropical Pacific, and (2) recently published paleoclimate data assimilation (DA) reconstructions. In the Palmyra coral data, superposed epoch analysis reveals a weak tendency for an El Niño-like response in the year after an eruption, but this response is not statistically significant, nor does it appear after the outsized 1257 Samalas eruption. In the DA reconstructions, the response is more nuanced, but provides limited evidence for an El Niño-like response of the tropical Pacific in the year following sufficiently large tropical volcanic eruptions. However, inconsistencies in both the spatial patterns and magnitudes between climate models and the DA reconstruction results indicate that current models may not adequately represent the regional tropical response of ENSO to volcanic forcing. Additionally, the Palmyra record represents the longest, best replicated, highest-resolution, and most proximal record to the center of ENSO variability currently available, while DA inherently incorporates model biases in the assimilation prior. Taken together, our results suggest that those models showing a strong ENSO response to volcanic forcing may overestimate the size of the forced response relative to natural ENSO variability.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMOS021..05D
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSES;
- 1630 Impacts of global change;
- GLOBAL CHANGE;
- 4215 Climate and interannual variability;
- OCEANOGRAPHY: GENERAL;
- 4922 El Nino;
- PALEOCEANOGRAPHY