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Effects of increased isopycnal diffusivity mimicking the unresolved equatorial intermediate current system in an earth system climate model
Author(s) -
Getzlaff Julia,
Dietze Heiner
Publication year - 2013
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/grl.50419
Subject(s) - isopycnal , thermal diffusivity , environmental science , geology , climatology , salinity , atmospheric sciences , oxygen , oceanography , chemistry , thermodynamics , physics , organic chemistry
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 ∼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.