[Department of Ocean Science] PhD Qualifying Examination Defense Seminar: Dissolved Organic Carbon Transport Simulation: Integrating Vertically Resolved Ocean Optics and Physical-Biogeochemical Modeling
 

Abstract: 

Dissolved organic carbon (DOC) is a key component of the coastal carbon cycle, linking terrestrial carbon export, biological production, and oceanic carbon transformation. However, accurately simulating DOC transport remains challenging because observations are spatially limited, remote sensing provides only indirect surface constraints, and numerical models require improved representations of both biogeochemical processes and underwater optical environments. This study develops an observation-constrained framework for DOC transport simulation by integrating vertically resolved ocean optics with physical–biogeochemical modeling. A vertically resolved visible attenuation scheme (KVIS) is developed by combining satellite observations and BGC-Argo profiles to reconstruct three-dimensional light attenuation fields and improve the representation of underwater light in regional ocean models. Validation across contrasting oceanic regions demonstrates that KVIS produces more realistic solar radiation penetration, upper-ocean stratification, and thermal structures compared with conventional simplified optical schemes. In parallel, chromophoric dissolved organic matter (CDOM) dynamics in the Pearl River Estuary are investigated using multi-year observations and a three-endmember mixing framework, incorporating riverine, surface, and subsurface water masses to provide physically constrained CDOM distributions. These optical constraints establish a pathway for linking remote sensing observations with DOC estimation and model initialization. Together, this work integrates observations, satellite remote sensing, vertically resolved optics, and physical–biogeochemical modeling toward the development of a coupled ROMS–KVIS–CoSiNE framework for three-dimensional DOC transport simulation. The proposed approach provides improved representation of light-driven processes and observational constraints for understanding coastal carbon cycling and terrestrial DOC export.