Diverse Arctic Oscillation responses after volcanic eruptions at different latitudes during the last millennium

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<p>This study conducted a comprehensive analysis of climate responses to volcanic eruptions occurred at different latitudes considering the last millennium volcanic eruptions available from Community Earth System Model ensemble simulations. Especially, we examine how different eruption latitudes induce the different responses in Arctic Oscillation (AO) with polar vortex and thereby exert different influences on northern Eurasian climate. We classify volcanic eruptions as tropical, northern and southern eruptions based on hemispheric aerosol loading ratios, which have different meridional structure of solar radiation perturbations and cause asymmetric climate response patterns between hemispheres, including tropospheric cooling and lower stratospheric warming. Volcanic eruptions found to cause stronger stratospheric polar vortex in both hemispheres with varying magnitudes depending on eruption latitudes. Following the tropical and southern eruptions, polar vortex enhancement is found in both hemispheric polar regions due to enhanced pole-to-equator temperature gradient and equatorward propagation of planetary waves. As a result of boreal winter averaged polar vortex enhancement, the tropical and southern eruptions found to cause more probability to occur at least the pentad strong polar vortex events during the boreal winter, which leads tropospheric westerly wind anomalies after a few days to the events. As a result, positive AO-like responses emerge at the lower troposphere. The positive AO induces surface air temperature warming as well as precipitation increase over the northern Eurasian continental regions. Following southern eruptions, the AO, Eurasian warming and wetting responses are much more extended to more southward (NH mid-latitudes) due to the more equatorward extended polar vortex variation. On the other hand, the Arctic polar vortex and the associated surface responses are only weakly influenced by the northern eruptions, in line with much poleward spread of volcanic aerosols and lesser equatorward extended planetary wave propagation in the lower stratosphere. These results suggest that while volcanic eruptions modulate surface climate by strengthening the polar vortex, their impacts are dependent on the eruption latitudes.</p>