This section was contributed by Keith Dixon ( kd@gfdl.gov), with modifications made for the free surface height by Eli Tziperman ( ett@gfdl.gov) and Stephen Griffies ( smg@gfdl.gov).
It is sometimes useful to allow water masses which are separated by land to exchange tracer properties. A case in point is when model grid resolution is too coarse to resolve narrow passageways which in reality connect water masses. For example, insufficient resolution may close off the Mediterranean from the Atlantic at Gibraltar, or the Arctic from the Pacific in the Bering Strait region.
Option xlandmix allows researchers to establish communication between bodies of water separated by land. The communication consists of mixing tracers between non-adjacent water columns. Momentum is not mixed. If the explicit free surface is enabled, option xlandmix_eta allows for the mixing of free surface height.
The scheme conserves tracers and volume. Its influence on tracers is tracked in the MOM diagnostics as part of the tracer source terms.