Using O2/Ar ratios to to assess biological production and near-surface vertical vertical mixing in global general circulation models on daily to seasonal timescales.

We assess the ability of ocean biogeochemical models to represent seasonal structures in net community production (NCP) in the Southern Ocean. Two models are compared to observations on daily to seasonal timescales in four different sections of the region. We use in situ observations of O2 and Ar supersaturation (ΔO2 / Ar) to estimate NCP. ΔO2 / Ar is converted to the flux of biologically generated O2 from sea to air (O2 bioflux). All data are aggregated to a climatological year with a daily resolution. To account for potential regional differences within the Southern Ocean, we conduct separate analyses of sections south of South Africa, around the Drake Passage, south of Australia, and south of New Zealand. 

Our results show that the models have a high skill in simulating ranges of net community production in the southern ocean, including latitudinal gradients. There are, however, large discrepancies in timing and regional structures. Certain patterns in our results suggests that physical processes, especially vertical transports, play a significant part in the spread between observations and model simulations. This suggests that oxygen fluxes and, in particularly, O2/Ar ratio can be used to validate the skill in general circualtion models.