Surface and Subsurface Biogeochemical Impacts of the 2019 Northeast Pacific Marine Heatwave

Abstract Following the highly impactful 2013–2016 Marine Heatwave (MHW), another MHW occurred in the Northeast Pacific during summer 2019. While the physical drivers of this event are well described, its biogeochemical impacts remain poorly understood. We use Ocetrac, a Python package that tracks spatiotemporal extreme events, to identify physical and biogeochemical anomalies associated with the 2019 MHW within two observation‐based products, GOBAI‐O 2 and MOBO‐DIC, and model output from the Community Earth System Model Forced Ocean Sea Ice Reconstruction (FOSI). Our findings reveal that warm temperature anomalies associated with the MHW negatively correlate with dissolved inorganic carbon (DIC) and dissolved oxygen (DO). Model reconstruction suggests that DIC anomalies were driven by air‐sea flux and biological processes, while anomalies in DO are linked to air‐sea flux and circulation. These results underscore the utility of new observational products and models for assessing the biogeochemical consequences of MHWs.