Publication Abstracts

DallaSanta and Polvani 2022, accepted

DallaSanta, K., and L.M. Polvani, 2022: Volcanic stratospheric injections up to 160 Tg(S) yield a Eurasian winter warming indistinguishable from internal variability. Atmos. Chem. Phys., accepted.

Early observational and modeling work suggested that low-latitude volcanic eruptions, comparable to the one of Pinatubo in 1991 or Krakatau in 1883, cause substantial surface warming over the northern continents at midlatitudes in wintertime. The proposed mechanism consists of the formation of an anomalously strong equator-to-pole temperature gradient in the stratosphere due to the presence of volcanic aerosols in the tropics, which is accompanied by an acceleration of the stratospheric polar vortex, which then shifts the Northern Annular Mode into a positive phase, resulting in warming surface temperatures over Eurasia.

However, a large body of research in the last decade has shown that, for eruptions such as Pinatubo or Krakatau, no such warming is seen in simulation with more recent climate models which, in general, have much finer vertical and horizontal resolution than the early ones, and which have separated the forced response from the internal variability by using large ensembles of integrations. Since the proposed mechanism is fundamentally sound, it is then possible that the 1991 Pinatubo eruption is simply not strong enough, but larger ones might indeed cause Eurasian surface warming in winter.

In this study, we explore this possibility using a state-of-the-art, stratosphere-resolving climate model, forced with prescribed volcanic aerosols from the Easy Volcanic Aerosol protocol. We consider eruptions with stratospheric sulfur injections of 5, 10, 20, 40, 80, and 160 Tg(S). With 20-member ensembles, we find that with injections of 20 Tg(S) or more — roughly twice the amplitude of Pinatubo and Krakatau eruptions — our model simulates a winter surface warming over Eurasia, which is statistically significant with a t-test given our 20-member ensembles. However, for all injection masses up to 160 Tg(S), the forced volcanic signal on Eurasian winter surface temperatures is so small as to be practically indistinguishable from internal variability.

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BibTeX Citation

@unpublished{da04300i,
  author={DallaSanta, K. and Polvani, L. M.},
  title={Volcanic stratospheric injections up to 160 Tg(S) yield a Eurasian winter warming indistinguishable from internal variability},
  year={2022},
  journal={Atmos. Chem. Phys.},
}

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RIS Citation

TY  - INPR
ID  - da04300i
AU  - DallaSanta, K.
AU  - Polvani, L. M.
PY  - 2022
TI  - Volcanic stratospheric injections up to 160 Tg(S) yield a Eurasian winter warming indistinguishable from internal variability
JA  - Atmos. Chem. Phys.
ER  -

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