Recent advances in metagenomics have demonstrated a global partitioning of the oceans into microbial biogeographical provinces. Such microbial communities participate in various biogeochemical processes that are critical to planetary-level ecosystem services. It’s unclear, however, what are the driving biological and environmental features of each province, and how they may respond under climate change. Using a dataset of over two thousand surface-water metagenomes of the prokaryotic size fraction, we employed a sequence abundance profiling approach to identify provinces and their defining features at the taxonomic and functional levels. By integrating such metagenomic data with environmental data layers, we projected province areas across oceans and modelled their dynamics under different climate change scenarios. Provinces follow a broad latitudinal gradient correlated with ocean temperature and nutrients but are influenced by physical factors such as coastal processes and ocean currents. Province area shifts under climate change are concentrated around coastal regions, areas with sharp environmental gradients and in the Arctic Ocean. Representative communities of provinces display a wide phylogenetic breadth but reflect key taxa in the marine ecosystem such as Prochlorococcus, Pelagibacter, Polaribacter, and Nitrosopumilus. At the functional level, pathways for discriminating between provinces include photosystems and chlorophyll binding, carotenoid biosynthesis, antibiotic resistance, and degradation of organic compounds. Our integrated analysis describes multiple aspects of biological variation across oceanic provinces and expands upon recent discoveries. This work pushes towards a unified framework for the study of marine microbial biogeography under a changing climate.