Southern Europe and western Asian marine heatwaves (SEWA-MHWs): a dataset based on macroevents

Marine heatwaves (MHWs) induce significant impacts on marine ecosystems. There is a growing need for knowledge about extreme climate events to better inform decision-makers on future climate related risks. Here we present a unique observational dataset of MHW macroevents and their characteristics over the southern Europe and western Asian (SEWA) basins, named the SEWA-MHW dataset (https://doi.org//10.5281/zenodo.7153255; Bonino et al., 2022). The SEWA-MHW dataset is derived from the European Space Agency Sea Surface Temperature Climate Change Initiative (ESA SST CCI) v2 dataset, and it covers the 1981-2016 period. The methodological framework used to build the SEWA-MHW dataset is the novelty of this work. First, the MHWs detected in each grid point of the ESA CCI SST dataset are relative to a time-varying baseline climatology. Since intrinsic fluctuation and anthropogenic warming are redefining the mean climate, the baseline considers both the trend and the time-varying seasonal cycle. Second, using a connected component analysis, MHWs connected in space and time are aggregated in order to obtain macroevents. Basically, a macroevent-based dataset is obtained from a grid cell-based dataset without losing high-resolution (i.e., grid cell) information. The SEWA-MHW dataset can be used for many scientific applications. For example, we identified phases of the well-known MHW of summer 2003, and taking advantage of statistical clustering methods, we clustered the largest macroevents in SEWA basins based on shared metrics and characteristics.