Effects of Ocean Mesoscale Processes on Biogeochemistry

Mesoscale processes contemplate movements in the ocean ranging from tens to hundreds of kilometers. At this scale it is possible to observe phenomena such as eddies, vortices, fronts among others. These processes are of great importance to biogeochemical cycles as they, for example, can affect the transport of nutrients to the euphotic zone by vertical movements, alter the mixed layer depth through vertical displacement of isopycnals, as well as trap biological, chemical and physical properties inside eddies and meanders.
Ocean General Circulation Models (OGCM’s) either resolve the mesoscale eddies by increasing the model resolution or parameterize them. The chosen approach regarding the eddies comes with some caveats as it can lead to simulations limited to small time periods or substantial simplifications of the physical processes, which in turn can alter results and obtain a different configuration for ocean and atmosphere dynamics. Regarding biogeochemical tracers, how eddies are represented in the model bring different outcomes, showing solutions that are model dependent such as ocean regions acting as a net source or sink of nutrients, oxygen and carbon. Hence we can’t accurately constrain the ocean’s role as a carbon sink. Not only the results are model dependent, but also resolution dependent. Ocean models with higher resolutions indicate that the vertical profiles of salinity and temperature are substantially altered by mesoscale activity, thus it is expected that biogeochemical tracers are altered by eddy induced disturbances.
We present some preliminary results of the output of the HAMburg Ocean Carbon Cycle model (HAMOCC; Ilyina et al 2013, Jungclaus et al 2020) in a 40 km and 10 km resolution on a global setup. As a result we show how changing the resolution affect on the upper ocean and mixed layer the major biogeochemical tracers and overall the carbon cycle.