Sediment Biogeochemistry Model Intercomparison Project (SedBGC_MIP): motivation and guidance for its experimental design

Benthic biogeochemical models are critical for understanding and predicting seafloor processes that regulate ocean chemistry, carbon sequestration, benthic habitat conditions, and climate feedbacks. However, current sediment models have limited predictive capabilities with widely variable complexity, structure, and underlying assumptions, highlighting a lack of consensus on essential process representations. To address this issue, this paper introduces the Sediment Biogeochemistry Model Intercomparison Project (SedBGC_MIP), a community-driven initiative aimed at systematically comparing existing benthic models against available observational constraints to refine key parameterizations and assess structural uncertainties. We review the state of sediment biogeochemical modeling, highlighting discrepancies in the representation of carbon cycling, burial, and redox remineralization processes across different model complexities. Through case studies, we demonstrate how varying model structures and ecosystem dynamics create uncertainty in global predicted biogeochemical feedbacks. We outline the objectives of SedBGC_MIP, including the need for standardized benchmarking, observational datasets, and cross-disciplinary collaboration to improve model skill and integration into Earth System Models. Ultimately, SedBGC_MIP aims to advance our ability to simulate benthic processes with greater accuracy, enhancing projections of ocean biogeochemistry under climate change scenarios with new capacity to address emerging living marine resource and geoengineering applications.