OCE-PRF: What controls the fate of biogenic particulate carbon in the ocean's twilight zone? Global-scale insights from data-constrained models

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This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).This fellowship project will address two fundamental questions about the ocean’s carbon cycle: (1) what controls the efficiency of particulate organic carbon (POC) transfer through the mesopelagic zone (100–1000 m), and (2) what causes shallow water column (1000 m depth) calcium carbonate (CaCO3) dissolution? Our ability to assess the impact of climate change on the ocean-atmosphere carbon dioxide (CO2) balance requires a predictive understanding of vertical POC transport, whereas a mechanistic understanding of shallow-water CaCO3 dissolution is needed to better predict the future state of ocean acidification. These two key issues will be addressed in the proposed project via the development of predictive, usable models that include the main physical and biogeochemical processes thought to control the vertical penetration of biogenic POC and CaCO3 into the ocean interior. All models and model output resulting from the proposed activity will be made available to any investigator who wishes to work with them through BCO-DMO. The publicly available models will allow the ocean biogeochemistry community to investigate how oceanic carbon sequestration will change in response to climate change.The overarching goal of the proposed project is to incorporate the effects of biogenic particle transport, transformation and removal processes into a mechanistic modeling framework that is suitable for implementation in Earth System models of intermediate complexity. The focus of model development will be on the treatment of unresolved processes including zooplankton-mediated particle breakup. The synergistic approach combines prognostic ocean biogeochemical models, data-constrained ocean circulation inverse models, and new sources of observational data to provide both the conceptual frameworks for model formulations and the model formulations themselves. POC flux and POC concentration profiles derived from field data, biogeochemical observations made available by the Biogeochemical Argo program, ocean carbon data from the Global Ocean Ship-Based Hydrographic Investigations Program, and Global Ocean Data Analysis Project and World Ocean Atlas data products will provide essential constraints on the underlying particle dynamics of the mesopelagic zone. The models resulting from the proposed activity can be applied to important scientific questions such as understanding oceanic carbon sequestration in a changing climate.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.