Global thermohaline circulation. Part 2: Sensitivity with interactive atmospheric transports

Journal Article · Fri Jan 01 04:00:00 EST 1999 · Journal of Climate

DOI:https://doi.org/10.1175/1520-0442-12.1.83· OSTI ID:323735

Wang, X; Stone, P H; Marotzke, J ^[1]

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1. Massachusetts Inst. of Tech., Cambridge, MA (United States). Center for Global Change Science

A hybrid coupled ocean-atmospheric model is used to investigate the stability of the thermohaline circulation (THC) to an increase in the surface freshwater forcing in the presence of interactive meridional transports in the atmosphere. The ocean component is the idealized global general circulation model used in Part 1. The atmospheric model assumes fixed latitudinal structure of the heat and moisture transports, and the amplitudes are calculated separately for each hemisphere from the large-scale sea surface temperature (SST) and SST gradient, using parameterizations based on baroclinic stability theory. The ocean-atmosphere heat and freshwater exchanges are calculated as residuals of the steady-state atmospheric budgets. Owing to the ocean component`s weak heat transport, the model has too strong a meridional SST gradient when driven with observed atmospheric meridional transports. When the latter are made interactive, the conveyor belt circulation collapses. A flux adjustment is introduced in which the efficiency of the atmospheric transports is lowered to match the too low efficiency of the ocean component. The feedbacks between the THC and both the atmospheric heat and moisture transports are positive, whether atmospheric transports are interactive in the Northern Hemisphere, the Southern Hemisphere, or both. However, the feedbacks operate differently in the northern and southern Hemispheres, because the Pacific THC dominates in the Southern Hemisphere, and deep water formation in the two hemispheres is negatively correlated. The feedbacks in the two hemisphere do not necessarily reinforce each other because they have opposite effects on low-latitude temperatures. The model is qualitatively similar in stability to one with conventional additive flux adjustment, but quantitatively more stable.

• Sponsoring Organization: USDOE, Washington, DC (United States); National Inst. for Global Environmental Change, Davis, CA (United States)
• DOE Contract Number: FC03-90ER61010
• OSTI ID: 323735
• Journal Information: Journal of Climate, Journal Name: Journal of Climate Journal Issue: 1 Vol. 12; ISSN JLCLEL; ISSN 0894-8755
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
EARTH ATMOSPHERE
ENVIRONMENTAL TRANSPORT
FRESH WATER
GLOBAL ASPECTS
MATHEMATICAL MODELS
OCEANIC CIRCULATION
WATER VAPOR