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 not complete. 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 identify its role. In this presentation, we will discuss how two different DOE program projects (SEAHORÇE and InteRFACE) are working towards a better representation of coastal carbon cycle dynamics in MPAS-Ocean and E3SM.

As a part of the Study for Exascale Advances in a High-resolution Ocean using ROMS Coupled to E3SM (SEAHORÇE) project, 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. The transport and fate of coastally sourced carbon tracers are examined in this framework.

Within the Interdisciplinary Research for Arctic Coastal Environments (InteRFACE) project, high-fidelity large eddy simulations are being used to better understand and parameterize in E3SM and MPAS-Ocean the role wave-ice interactions and ice floe distributions play in light penetration and phytoplankton blooms in the coastal and open-ocean Arctic. These results have implications for the export of coastally sourced carbon off-shelf and into the deep ocean.