The oceans constitute the largest carbon reservoir at Earth’s surface and play a central role in regulating atmospheric CO₂ concentrations over geologic time. Consequently, short- and long-term variations in oceanic geochemical cycles have exerted strong, compounding influences on the evolution and present state of Earth’s atmosphere and biosphere. Despite extensive efforts to characterize marine geochemical cycles, several fundamental questions remain, including: (i) how changes in continental weathering and hydrothermal circulation have influenced ocean composition through geologic time, and (ii) how the availability of key nutrients in seawater has affected the evolution of life and the composition of the atmosphere.

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In addition to earlier work on feedbacks between seawater composition and hydrothermal fluid chemistry through the Phanerozoic (Antonelli et al., 2017, PNAS), Antonelli published an important manuscript reassessing the radiogenic ⁴⁰Ca budget of seawater. This study confirms that continental Ca inputs—enriched in ⁴⁰Ca through the decay of ⁴⁰K—rather than hydrothermal circulation, represent the dominant source of Ca to the modern oceans (Antonelli et al., 2021, ACS Earth Space Chem). He is also involved in multiple ongoing projects, in collaboration with D. DePaolo (University of California, Berkeley) and others, focused on understanding alteration processes affecting ocean-floor basalts and peridotites.