SOMHW4D: a circumpolar dataset of four-dimensional marine heatwave events in the Southern Ocean

Amid ongoing climate change, marine heatwaves (MHWs) have received increasing attention due to their impacts on marine ecosystems and human societies. In the Southern Ocean, MHWs may exert profound effects on regional ecosystems by altering sea-ice conditions, primary productivity, and habitat conditions for species. Although publicly available tools have provided standardized approaches for MHW identification, existing studies have mainly focused on the sea surface or individual depth layers, making it difficult to characterize the three-dimensional structure of MHWs within the water column and their continuous spatiotemporal evolution. This limitation constrains a comprehensive assessment of the ecological impacts of MHWs. Here, we developed the Southern Ocean Marine Heatwave 4D dataset (SOMHW4D), a circumpolar four-dimensional MHW dataset for the Southern Ocean from 1993 to 2025 based on the GLORYS12V1 reanalysis. SOMHW4D identifies MHWs within a longitude–latitude–depth–time framework. By constructing daily three-dimensional connected objects and tracking them between consecutive time steps, the dataset represents MHWs as continuously evolving four-dimensional thermal anomaly structures. SOMHW4D provides three levels of data products: grid-level, three-dimensional object-level, and event-level data, including MHW occurrence and intensity information, daily three-dimensional thermal anomaly structures, and four-dimensional tracking results. Grid-level and three-dimensional object-level data are provided as NetCDF files, together with event-level summary tables. SOMHW4D provides a systematic data basis for characterizing the spatial distribution, vertical structure, and lifecycle evolution of MHWs in the Southern Ocean, and can support studies of MHW ecological impacts.