Marine heatwaves (MHWs) are oceanic extreme events characterized by prolonged periods of unusually high sea surface temperatures. MHWs cause devastating effects on biological communities and marine ecosystems. MHW events can last from days to years and move across ocean basins. While MHWs have traditionally been studied across grid cells, recent work has explored the spatiotemporal representation of MHWs. Here, we use Ocetrac, a python package for identifying and tracking spatially connected MHWs, to study the spatiotemporal evolution of MHWs and to understand their drivers, impacts, and prediction. First, we evaluate drivers of large North Pacific MHWs in a large ensemble of climate simulations using the Community Earth System Model (CESM). We demonstrate that regional MHWs are controlled by different atmospheric drivers and are related to climate modes like the Pacific Decadal Oscillation and El Niño. Next, we investigate the biogeochemical impacts of the Blob 2.0, a consequential MHW that occurred in the Northeast Pacific in summer 2019. We use CESM and a set of observational datasets to show that warm temperature anomalies associated with the Blob 2.0 negatively correlate with dissolved inorganic carbon and dissolved oxygen. Finally, we evaluate global spatiotemporal forecasts of MHWs and develop intuitive metrics that demonstrate long-term forecast skill of MHW area, location, and intensity. Together, these studies improve our understanding of MHWs and advance our capabilities to plan for and respond to extreme ocean temperatures.

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