Parameterizing the Impact of Mesoscale Eddies on Earth System Processes in the Energy Exascale Earth System Model
Mesoscale eddies are the "weather" of the ocean, high and low pressure systems 10-100 km across that are found throughout the global ocean. These eddies play an important role in the Earth System by homogenizing tracers such as temperature, salinity and oxygen along surfaces of constant density in the interior and horizontally in the mixed layer and by fluxing momentum in the vertical. While the latter role has been well studied and is represented in models such as E3SM, a great deal of disagreement exists about how to the former effect should be represented. This is problematic, as the magnitude of this coefficient has impacts on physical climate, particularly in convective regions, the distribution of oxygen in the ocean interior and the uptake of anthropogenic carbon dioxide.In this project we build on work done over the past decade to explore the impact of lateral mixing within climate models to improve its representation within E3SM.
Preliminary exploration of the E3SM code has raised questions about whether the lateral mixing parameterization is numerically stable. We are examining this question in more detail before proposing revisions to the code as well as testing ocean-only formulations of tracer uptake that can be easily benchmarked against observations. We are also continuing to document the impact of lateral mixing in lower-resolution climate models, providing a benchmark with which to compare E3SM.