Arctic warming contributes to increase in Northeast Pacific marine heatwave days over the past decades

Abstract

The increase in marine heat wave days in the Northeast Pacific ocean over the past few decades is linked to Arctic warming and sea ice decline, according to analyses of satellite-derived and reanalysis data along with idealized coupled climate model experiments. The frequency and duration of marine heatwaves have been increasing with ocean warming due to climate change. In particular, the Northeast Pacific has experienced intense and extensive marine heatwaves since the late 1990s - characteristically called "the Blob". Here, an investigation of satellite-derived and reanalysis data supported by idealized coupled model experiments show that Arctic warming plays an important role in the increase in Northeast Pacific marine heatwave days during boreal summers. Strong Arctic warming has acted to change the atmospheric circulation pattern over the Northeast Pacific and reduce the low-level cloud fraction from late spring to early summer. We show that the enhancement of solar radiative heat fluxes and reduced latent heat loss over a relatively large area has favored an increase in sea surface temperatures and marine heatwave days. An idealized model experiment performed here, designed to isolate the impact of Arctic warming, supports this hypothesis. The projected changes of Arctic climate on the occurrence of marine heatwaves should be considered in climate change adaptation and mitigation plans.