Preprints
https://doi.org/10.5194/egusphere-2024-1302
https://doi.org/10.5194/egusphere-2024-1302
21 May 2024
 | 21 May 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Long-lasting high-latitude volcanic eruptions as a trigger for sudden stratospheric warmings: An idealized model experiment

Hera Guðlaugsdóttir, Yannick Peings, Davide Zanchettin, and Guðrún Magnúsdóttir

Abstract. The temporary enhancement of the stratospheric aerosol layer after major explosive volcanic eruptions can trigger climate anomalies beyond the duration of the radiative forcing. Whereas the mechanisms responsible for long-lasting response to volcanic forcing have been extensively investigated for tropical eruptions, less is known about the dynamical response to high-latitude eruptions. Here we use global climate model simulations of an idealized long-lasting (6 months) northern hemisphere high-latitude eruption to investigate the climate response during the first three post-eruption winters, focusing on the dynamics governing the stratospheric polar vortex. Our results reveal that two competing mechanisms contribute to determining the post-eruption evolution of the polar vortex: 1) A local stratospheric mechanism whereby increased absorption of thermal radiation by the enhanced aerosol layer yields a polar vortex strengthening via a thermal wind response. 2) A bottom-up mechanism whereby surface cooling yields an increase in atmospheric wave activity that propagates into the winter stratosphere, leading to a weakening of the polar vortex, also seen as an increased occurrence of sudden stratospheric warming events (SSWs). The local stratospheric mechanism dominates in the first post-eruption winter, while the bottom-up mechanism dominates in the follow-up winters. The identification of a deterministic response such as increased SSWs following high-latitude volcanic eruptions calls for increased attention to these events as an important source of interannual variability and a possible source of increased seasonal predictability of northern hemisphere regional climates.

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Hera Guðlaugsdóttir, Yannick Peings, Davide Zanchettin, and Guðrún Magnúsdóttir

Status: open (until 04 Jul 2024)

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Hera Guðlaugsdóttir, Yannick Peings, Davide Zanchettin, and Guðrún Magnúsdóttir
Hera Guðlaugsdóttir, Yannick Peings, Davide Zanchettin, and Guðrún Magnúsdóttir

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Short summary
Here we use an Earth System Model to simulate a long-lasting volcanic eruption at 65° N to assess its climate effects. We show a Polar Vortex strengthening in winter 1 and a weakening in winters 2–3 due to surface cooling that further causes an increase in sudden stratospheric warmings. This can cause severe cold weather events in the northern hemisphere. Our motivation is to understand how such eruptions impact the climate system for improving decadal climate predictability.