No study to date has investigated the long-term effects of high-latitude eruptions.

Here, we use a climate model to show that large summer high-latitude eruptions in the Northern Hemisphere cause strong hemispheric cooling, which could induce an El Niño-like anomaly, in the equatorial Pacific during the first 8–9 mo after the start of the eruption.

This experimental design was chosen as analog for one of the strongest high-latitude eruptions in historical time, the 1783 Laki eruption in Iceland.

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We discard the first 4 y to remove the hemispheric-wide cooling due the eruption.

The SD is calculated from the concatenated time series using all 10 members in each ensemble.

The bold green dashed lines show the ensemble-averaged position of the ITCZ in the no-volcano and volcano simulations.

() Ensemble average changes in near-surface wind (arrows) and SST (shading) 4–9 mo following the start of the eruption. The contours delineate the areas where the SST anomalies are significant at the 95% confidence level using a Student In light of our results, we find intriguing that the El Niño event that peaked in January of 1912, 6 mo before the Katmai eruption in June of 1912 (the largest high-latitude eruption of the 20th century), was immediately followed by near-normal conditions in the tropical Pacific rather than the La Niña conditions that normally occur after El Niño events.

Another El Niño event occurred a year after the eruption (, Fig. Furthermore, tree-ring data (22) suggest that the El Niño conditions preceding the Laki eruption were further strengthened in the winter of 1783–1784 (6–9 mo after the beginning of the eruption), in agreement with our findings.

However, further evidence would be needed to test our model results using observations.S9) increase the density of the surface water in the higher latitudes of the Northern Hemisphere that act to destabilize the water column, leading to enhanced oceanic convection in the North Atlantic (, Fig. The strengthening of the AMOC as well as the mechanisms involved are similar to those proposed for tropical eruptions (9, 10): here, we show that the impact on the AMOC is not limited to the first 10–20 y and to tropical eruptions as shown in previous studies (9) Long-term changes in the AMOC, as indicated by the change in the maximum of the overturning stream function (in sverdrups).The shading shows approximate 95% confidence intervals (twice the SEM) of the difference in all pairs of experiments that comprise the ensembles.Here, we use a coupled atmospheric–ocean–aerosol model [Norwegian Earth System Model: Nor ESM1-M (16, 17)] to identify the mechanisms by which high-latitude volcanic eruptions can impact ENSO behavior in both the short term (up to 2–3 y) and long term (approximately half-century), the latter being mediated by volcano-induced changes in ocean circulation.We simulate an extreme high-latitude multistage eruption starting on June 1st.Hence, 210 y of data are used to calculate the SD in ).