Annual metrics of Marine Heatwaves

The present dataset provides Annual metrics of Marine Heatwaves (MHWs) for the North Atlantic basin between 1982-2020. This dataset was derived from C3S and ESA CCI Sea Surface Temperature (SST) dataset, with 0.05 degrees of spatial resolution, following the Hobday's (2016) method as used in the following paper: Lopes, B., Oliveira, A., Silva, F., Paixão, J., & Gouveia, C. (2026). Marine Heatwaves and Ocean-Atmosphere Synergies in the North Atlantic. Preprints. https://doi.org/10.20944/preprints202606.0251.v1 MHWs were identified according to the Hobday et al. (2016) definition, with minor modifications. According to this definition, an MHW event occurs when the local temperature exceeds the 90th percentile threshold of the climatology for at least five consecutive days. Additionally, any gap of two days or less between subsequent events is considered part of the same continuous MHW event. To establish a reference climatology, the Hobday definition was modified by calculating both the mean and the 90th percentile of SST over the entire available historical period (1982–2022) for each calendar day, rather than using a fixed 30-year baseline. Additionally, a 15-day total running average window was applied, instead of a 30-day window used in Hobday’s definition, in order to reduce excessive inter-weekly smoothing. This dataset contains five Data Variables: number_of_events - Number of marine MHW events (frequency) occurring during each year. mean_annual_duration - Mean duration of MHW events within each year. max_annual_duration - Max duration of MHW events within each year. max_annual_intensity - Maximum intensity of MHW events during each year. mean_annual_intensity - Mean intensity of MHW events during each year. MHWs spanning two calendar years were assigned to the year in which they ended. This research was funded by Horizon Europe Project ObsSea4Clim: Ocean observations and indicators for climate and assessments (funded by the European Union, Grant Agreement number:101136548) and supported by the Recovery and Resilience Plan Investment RE-C05-i02: Interface Mission—CoLAB, certified by the National Innovation Agency (Project No. [M54.1]01/C05-i02/2022).