Journal ArticleDevelopment of a moored radium in situ sampler to measure annual time seriesKipp, Lauren [Department of Environmental Science Rowan University Glassboro New Jersey USA] (ORCID:0000000251119779); Charette, Matthew A [Department of Marine Chemistry & Geochemistry Woods Hole Oceanographic Institution Woods Hole Massachusetts USA] (ORCID:000000033699592X); Henderson, Paul [Department of Marine Chemistry & Geochemistry Woods Hole Oceanographic Institution Woods Hole Massachusetts USA]; Benedict, Joshua [Department of Environmental Science Rowan University Glassboro New Jersey USA]; Polyakov, Igor [International Arctic Research Center University of Alaska Fairbanks Fairbanks Alaska USA] (ORCID:0000000159128074); Pnyushkov, Andrey [International Arctic Research Center University of Alaska Fairbanks Fairbanks Alaska USA] (ORCID:0000000191126458)Radium is a useful tracer of sediment‐derived materials, improving our understanding of the geochemical cycling of elements at ocean boundaries. We have developed an autonomous in situ sampler to collect time series samples of radium isotopes on mooring deployments. Samplers were deployed for 2 yr in the Arctic Ocean, a region particularly hard to access outside of the summer season, and collected monthly samples to create the first annual time series of radium‐228 and radium‐226 in the Arctic. Results from the Laptev Slope show increased radium‐228 and radium‐228/radium‐226 ratios in spring/summer, concomitant with increased meteoric water and brine influence. Together, these tracers indicate seasonal periods of increased influence of shelf‐ and river‐derived materials, findings which would not be possible to discern from summertime shipboard surveys alone. The development of this in situ sampler has therefore expanded our capability to use radium as a tracer to discern temporal changes in the geochemistry of remote areas of the ocean.Wiley Periodicals LLC2025-12-0410662571Limnology and Oceanography: Methods1541-5856https://doi.org/10.1002/lom3.700202031853; 2031854National Science Foundation