While the land-ocean transition zone is dynamic, highly heterogeneous, and contains a diverse set of carbon sources and sinks, its role in the global carbon cycle, and how it will change in the future with increased anthropogenic pressures, is limited. The Model for Prediction Across Scales - Ocean (MPAS-Ocean), the ocean component of the DOE's Energy Exascale Earth System Model (E3SM), with its regional refinement and marine carbon cycle capabilities, is uniquely suited to help start identifying its role. In this presentation, we will discuss how three different EESM Program projects (Seahorce, InteRFACE, and E3SM-HES) are working towards a better representation of coastal carbon cycle dynamics in MPAS-Ocean and E3SM. 

As a part of the Seahorce SciDAC project (Study for Exascale Advances in a High-resolution Ocean using ROMS Coupled to E3SM), we are working on assessing E3SM and MPAS-Ocean's representation of the complex circulation of shallow shelves and ocean-shelf exchange (eg. submesoscale processes and river plume dynamics) around the Continental US as the minimum resolution in the regional refinement zones is pushed to kilometer scales. Within the InteRFACE project (Interdisciplinary Research for Arctic Coastal Environments), high-fidelity large eddy simulations are being used to better understand and parameterize small-scale coastal and open-ocean vertical mixing processes in the Arctic critical for the exporting of carbon off-shelf and into the deep ocean. Lastly, the Human-Earth System Feedbacks group within the E3SM project are working towards improving the overall efficiency of biogeochemical and carbon dynamics in E3SM, reducing the overall computation cost, as well as developing new analysis tools for evaluating marine carbon dynamics in E3SM.