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

Abstract

Abstract. 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.