Diagnostic modeling of oceanic biogeochemical fluxes using a general ocean turbulence model (GOTM) and time-series tracer measurements

This work addressed the ocean biogeochemical context of two climate-relevant gases: carbon dioxide (CO2) and dimethylsulfide (DMS). We combined time-series measurements and a model of ocean physics to conduct two diagnostic modeling studies.;The objective of the first case study was to estimate gross biological DMS production rates in the coastal Southern Ocean, west of the Antarctic Peninsula, near Palmer Station. A combination of field measurements from the 2005--2006 DMS sampling season and a physical model of ocean mixing were combined into a diagnostic model of DMS production. The average DMS production rate in the water column was estimated at 3.3 +/- 0.5 nM d-1. When diagnosed production rates were normalized by DMSP concentrations, we found a strong similarity between our estimates and the results obtained by others in a contrasting biogeochemical environment, the North Atlantic subtropical gyre. We, therefore, propose that the average DMSP to DMS conversion rate might be independent of the biogeochemical environment and place our estimate at 0.07 +/- 0.01 (nM DMS d-1)/(nM DMSP).;In the second case study, hydrographic and biogeochemical field measurements from the 1996--1998 sampling seasons at the European Station for Time-series in the Ocean, Canary Islands (ESTOC) were used together with a physical model of ocean mixing to diagnose net biological fluxes of nutrients, oxygen, and carbon. On the annual basis ESTOC appeared to be close to metabolic balance, with interannual fluctuations between net autotrophy and net heterotrophy. Our results suggest that export production at the site is indistinguishable from zero.