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Atlantic pycnocline theory scrutinized using a coupled climate model
Author(s) -
Levermann Anders,
Fürst Johannes Jakob
Publication year - 2010
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 - 10.1029/2010gl044180
Subject(s) - pycnocline , thermohaline circulation , climatology , upwelling , forcing (mathematics) , zonal and meridional , geology , wind stress , oceanography , ocean general circulation model , ocean current , atmospheric sciences , climate change , general circulation model
Simulations with changed Southern Ocean wind‐stress, oceanic vertical mixing, surface freshwater forcing and global warming confirm the basic equations of Gnanadesikan's (1999) theory for the Atlantic: one vertical scale, the pycnocline depth D , contributes inversely proportional to low‐latitudinal upwelling and linearly to Southern Ocean eddy transport. The maximum Atlantic overturning is confirmed to be quadratic in D but is also shown to be linear in a meridional density difference Δ ρ . Our simulations strongly suggest that the theory needs to be complemented by a dynamical equation for Δ ρ since changes in both D and Δ ρ are significant and mutually independent. While, under global warming D varies strongly and Δ ρ is practically constant, the situation is reversed for altered surface freshwater fluxes. Similarly, variations in the meridional length scale of Southern Ocean outcropping require a dynamical equation in order to capture the fundamental behavior of the Atlantic meridional overturning circulation.