Tara Polaris expeditions: Seasonal and long-term contaminant monitoring in the changing central Arctic

The central Arctic, a critical sentinel of global environmental change, is increasingly impacted by both legacy and emerging contaminants transported through atmospheric, oceanic, riverine, and cryospheric pathways. The Tara Polaris expeditions introduce an integrated and year-round approach to central Arctic contaminant monitoring by combining multi-compartment observations of mercury, anthropogenic lead, plastics across nano- to macro-scales, and chemicals of emerging arctic concern, including per- and polyfluoroalkyl substances. This framework aims to investigate contaminant sources, transport pathways, seasonal dynamics, internal cycling, environmental fate, and associated ecotoxicological risks across the atmosphere, snow, sea-ice, seawater, and biological compartments of the central Arctic. Particular emphasis will be placed on microbially mediated processes, including mercury methylation, plastic degradation, and the role of microbial communities in contaminant transformation and ecosystem resilience. The program will also investigate contaminant exchanges across key environmental interfaces, including the snow–ice–ocean continuum, and assess how ongoing sea-ice decline and changing Arctic environmental conditions may influence contaminant redistribution and exposure pathways in Arctic ecosystems. By coupling contaminant measurements with microbial, biogeochemical, and omics-based approaches, the program will help resolve critical uncertainties regarding contaminant behavior in a rapidly changing Arctic. The resulting high-resolution datasets over complete annual cycles will support the development of predictive models describing contaminant dynamics under ongoing climate warming and increasing anthropogenic pressures. It will further provide a comprehensive baseline for future Arctic observing efforts and international long-term monitoring programs in the central Arctic.