A modeling study of the seasonal oxygen budget of the global ocean

Abstract

[1] An ecosystem model embedded in a global ocean general circulation model is used to quantify roles of biological and physical processes on seasonal oxygen variations. We find that the thermally induced seasonal net outgassing (SNO) of oxygen is overestimated by about 30% if gas phase equilibrium is assumed, and we find that seasonal variations in thermocline oxygen due to biology are approximated well using the oxygen anomaly. Outside the tropics and the north Indian Ocean, biological SNO is, on average, 56% of net community production (defined as net oxygen production above 76 m) during the outgassing period and 35% of annual net community production. In the same region the seasonal drawdown of the oxygen anomaly within the upper thermocline (76-500 m) is 76% of the remineralization during the drawdown and 48% of annual remineralization. Applying model-derived relationships to observed O 2 climatologies and using independent estimates for tropical and monsoonal systems, we estimate global net community production to be 14.9 ± 2.5 Pg C yr À1 .

Mechanisms governing interannual variability in upper-ocean inorganic carbon system and air–sea CO2 fluxes: Physical climate and atmospheric dust

“…But an analysis of only the model surface layer folds in additional complications because of strong vertical mixing in the mixed layer ARTICLE IN PRESS and fact that subsurface biological carbon uptake/release can be transported by vertical mixing/advection into the surface layer. An integration depth of 100 m was chosen as a compromise, as this is below the annual mean mixed layer in the model for a large fraction of the globe and is the approximate depth of net biological carbon uptake in the model (e.g., Jin et al, 2007). Using the linear expansion in Eq.…”

Impact of variable air-sea O<sub>2</sub> and CO<sub>2</sub> fluxes on atmospheric potential oxygen (APO) and land-ocean carbon sink partitioning

“…A similar equation was used to estimate the thermal component of the WHOI O 2 flux: F O 2 thermal =Q(dS O 2 /dT )/C p , but with two modifications recommended by Jin et al (2007), who optimized the formula based on comparisons to explicitly modeled thermal O 2 fluxes. First, the magnitude of F O 2 thermal was scaled down by a factor of 0.7 to account for incomplete thermal equilibration of O 2 .…”

“…The amplitude of the seasonal cycle in APO has been used to infer the rate of seasonal new production at the ocean basin or hemispheric scale (Bender et al, 1996;Balkanski et al, 1999;Najjar and Published by Copernicus Publications on behalf of the European Geosciences Union. 876 C. D. Nevison et al: Air-sea O 2 flux variability and its impact on APO Keeling, 2000), although temporal and spatial overlap between new production and ventilation cause uncertainties in the inferred rates (Nevison et al, 2005;Jin et al, 2007).…”

A determination of air-sea gas exchange and upper ocean biological production from five noble gases and tritiugenic helium-3

“…Biological production is incorporated through the use of an idealized oxygen production and consumption profile. The compensation depth is assumed to be 76 m for most runs (Najjar and Keeling, 1997;Jin et al, 2007). Above the compensation depth, the oxygen productivity profile, P rod, is represented by a sine curve.…”