Online tracer-coordinate diagnostics in MOM6

Examining the ocean in the coordinate frame of both active and passive tracers is a common approach in oceanography. The density-space overturning circulation and the watermass transformation framework are two widespread examples. To avoid prohibitive time-averaging errors, it is essential to do the coordinate transformation online. Here, I will present an update on efforts to develop this diagnostic capability in MOM6. The approach leverages the model's regrid-remap architecture, allowing model diagnostics to be output in the tracer coordinate at each location on the horizontal grid. This effort will allow time-averaged diagnostics output in the coordinate of any arbitrary physical or biogeochemical tracer (such as temperature, salinity, oxygen, or carbon) greatly improving the diagnostic capability of MOM6. Finally, I will highlight how this effort dovetails with other work developing robust diagnostics of watermass volume budgets.