Mitigating Summertime Marine Heatwaves via Targeted Marine Cloud Brightening

Matt Luongo , Edward Blanchard-Wrigglesworth, Kyle C. Armour, Haruki Hirasawa, Jacob T Cohen, Aaron Donohoe

Marine heatwaves (MHWs) negatively impact marine ecosystems and coastal economies. Here, we evaluate whether a preemptive, short-term, localized surface emission of sea salt aerosols (marine cloud brightening, MCB) can mitigate the impacts of a predicted MHW without creating significant effects beyond the intervention zone. As a case study, we apply MCB to the 2019 Northeast Pacific MHW, "The Blob 2.0," using a global climate model seasonal-to-multiyear predictability ensemble. Initiating MCB in May 2019 mitigates important negative consequences of the event, substantially reducing the MHW magnitude and limiting associated declines in surface oxygen. The impacts of this intervention are mostly local and limited to summer, even when MCB is extended into winter, with nonlocal climate effects smaller than internal variability. By demonstrating local efficacy and minor remote impacts for mitigating the Blob 2.0, this work motivates further study of whether localized and temporary climate interventions can safely and effectively mitigate MHWs.