Morgan E. J., Manizza M., Keeling R. F., Resplandy L., Mikaloff-Fletcher S. E., Nevison C. D., Jin Y. M., Bent J. D., Aumont Olivier, Doney S. C., Dunne J. P., John J., Lima I. D., Long M. C., Rodgers K. B. (2021). An atmospheric constraint on the seasonal air-sea exchange of oxygen and heat in the extratropics. Journal of Geophysical Research : Oceans, 126 (8), p. e2021JC017510 [20 p.]. ISSN 2169-9275.
Titre du document
An atmospheric constraint on the seasonal air-sea exchange of oxygen and heat in the extratropics
Année de publication
2021
Auteurs
Morgan E. J., Manizza M., Keeling R. F., Resplandy L., Mikaloff-Fletcher S. E., Nevison C. D., Jin Y. M., Bent J. D., Aumont Olivier, Doney S. C., Dunne J. P., John J., Lima I. D., Long M. C., Rodgers K. B.
Source
Journal of Geophysical Research : Oceans, 2021,
126 (8), p. e2021JC017510 [20 p.] ISSN 2169-9275
The air-sea exchange of oxygen (O-2) is driven by changes in solubility, biological activity, and circulation. The total air-sea exchange of O-2 has been shown to be closely related to the air-sea exchange of heat on seasonal timescales, with the ratio of the seasonal flux of O-2 to heat varying with latitude, being higher in the extratropics and lower in the subtropics. This O-2/heat ratio is both a fundamental biogeochemical property of air-sea exchange and a convenient metric for testing earth system models. Current estimates of the O-2/heat flux ratio rely on sparse observations of dissolved O-2, leaving it fairly unconstrained. From a model ensemble we show that the ratio of the seasonal amplitude of two atmospheric tracers, atmospheric potential oxygen (APO) and the argon-to-nitrogen ratio (Ar/O-2), exhibits a close relationship to the O-2/heat ratio of the extratropics (40-70 degrees). The amplitude ratio, A(APO)/A(ArN2), is relatively constant within the extratropics of each hemisphere due to the zonal mixing of the atmosphere. A(APO)/A(ArN2) is not sensitive to atmospheric transport, as most of the observed spatial variability in the seasonal amplitude of delta APO is compensated by similar variations in delta(Ar/N-2). From the relationship between O-2/heat and A(APO)/A(ArN2) in the model ensemble, we determine that the atmospheric observations suggest hemispherically distinct O-2/heat flux ratios of 3.3 +/- 0.3 and 4.7 +/- 0.8 nmol J(-1) between 40 and 70 degrees in the Northern and Southern Hemispheres respectively, providing a useful constraint for O-2 and heat air-sea fluxes in earth system models and observation-based data products. Plain Language Summary Typically, the surface of the ocean releases oxygen to the atmosphere during summer and takes it up during winter. This cycle is driven by circulation, biology (photosynthesis and respiration), and the seasonal cycle in water temperature, which changes the solubility of oxygen in surface water. We have used measurements of two atmospheric tracers, one which tracks oxygen and one which tracks heat, to estimate the amount of oxygen taken up or released by a change in ocean heat content. By looking at ocean models and atmospheric observations of the two atmospheric tracers, we find that the oxygen exchange between the ocean and atmosphere in the Southern Hemisphere is more responsive to changes in heat content than in the Northern Hemisphere. These hemispheric metrics are useful tests of how ocean models simulate some biological and physical processes.
Plan de classement
Sciences fondamentales / Techniques d'analyse et de recherche [020]
;
Sciences du milieu [021]
;
Limnologie physique / Océanographie physique [032]
Localisation
Fonds IRD [F B010082743]
Identifiant IRD
fdi:010082743
