Abstract
In this paper, we present the first global ocean-biogeochemistry model
that uses a telescoping high resolution for an improved representation
of coastal carbon dynamics: ICON-Coast. Based on the unstructured
triangular grid topology of the model, we globally apply a grid
refinement in the land-ocean transition zone to better resolve the
complex circulation of shallow shelves and marginal seas as well as
ocean-shelf exchange. Moreover, we incorporate tidal currents including
bottom drag effects, and extend the parameterizations of the model’s
biogeochemistry component to account explicitly for key shelf-specific
carbon transformation processes. These comprise sediment resuspension,
temperature-dependent remineralization in the water column and sediment,
riverine matter fluxes from land including terrestrial organic carbon,
and variable sinking speed of aggregated particulate matter. The
combination of regional grid refinement and enhanced process
representation enables for the first time a seamless incorporation of
the global coastal ocean in model-based Earth system research. In
particular, ICON-Coast embraces all coastal areas around the globe
within a single, consistent ocean-biogeochemistry model, thus naturally
accounting for two-way coupling of ocean-shelf feedback mechanisms at
the global scale. The high quality of the model results as well as the
efficiency in computational cost and storage requirements proves this
strategy a pioneering approach for global high-resolution modeling. We
conclude that ICON-Coast represents a new tool to deepen our mechanistic
understanding of the role of the land-ocean transition zone in the
global carbon cycle, and to narrow related uncertainties in global
future projections.