Journal
GEOPHYSICAL RESEARCH LETTERS
Volume 40, Issue 10, Pages 2166-2170Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1002/grl.50419
Keywords
earth system modeling; nutrient trapping; minimum zones; Pacific; oxygenation; denitrification
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Funding
- Deutsche Forschungsgemeinschaft [DI 1665/1-1, SFB754]
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Earth system climate models generally underestimate dissolved oxygen concentrations in the deep eastern equatorial Pacific. This problem is associated with the nutrient trapping problem, described by Najjar et al. [1992], and is, at least partially, caused by a deficient representation of the Equatorial Intermediate Current System (EICS). Here we emulate the unresolved EICS in the UVic earth system climate model by locally increasing the zonal isopycnal diffusivity. An anisotropic diffusivity of approximate to 50,000 m(2) s(-1) yields an improved global representation of temperature, salinity and oxygen. In addition, it (1) resolves most of the local nutrient trapping and associated oxygen deficit in the eastern equatorial Pacific and (2) reduces spurious zonal temperature gradients on isopycnals without affecting other physical metrics such as meridional overturning or air-sea heat fluxes. Finally, climate projections of low-oxygenated waters and associated denitrification change sign and apparently become more plausible.
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