The response of winter Pacific North American pattern to strong volcanic eruptions

Abstract

The impact of volcanic eruptions on large-scale atmospheric circulation patterns has been well studied, but very little effort has been made on relating the response of Pacific North American (PNA) pattern to strong volcanic eruptions. Here we investigate the response of winter PNA to the largest volcanic eruptions using three different reanalysis datasets. We demonstrate a significant positive PNA circulation response to strong volcanic forcing in the first winter following the eruptions. This circulation pattern is associated with enhanced southwesterly winds advecting warm air from the tropical/subtropical Pacific into northwestern North America and leads to a significant warming in the region. However, no significant PNA signal is found for the second post-eruption winter. The PNA responses to volcanic forcing depend partly upon the modulation of the El Niño Southern Oscillation (ENSO) events. When the ENSO influence is linearly removed, this positive PNA signal is still robust during the first post-eruption winter, albeit with slightly decreased magnitude and significance. Our findings provide new evidence for volcanic forcing of the Pacific and North American climates. The results presented here may contribute to deconvolving modern and past continental-scale climate changes over North America.