Response of a simplified oceanic general circulation model to idealized NAO-like stochastic forcing

• Published in: Journal of physical oceanography Vol. 32; no. 11; pp. 3182 - 3192
• Main Authors: HERBAUT, C, SIRVEN, J, FEVRIER, S
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 01.11.2002
• Subjects: Dynamics of the ocean (upper and deep oceans); Earth, ocean, space; Exact sciences and technology; External geophysics; Gyres; Oceanography; Physics of the oceans; Thermohaline circulation; Wind; Stochastic model; Sea surface; Sensitivity analysis; General circulation models; Ocean circulation; Thermohaline convection; Surface temperature; Wind effect; North Atlantic oscillation; Numerical simulation; Anomaly; Forcing; Vortex; Heat transfer
• ISSN: 0022-3670; 1520-0485
• DOI: 10.1175/1520-0485(2002)032<3182:ROASOG>2.0.CO;2

The response of a simplified model of the subtropical and subpolar gyres to a mechanical stochastic forcing that mimics the North Atlantic Oscillation (NAO) is studied. An internal damped mode of oscillation with a 22-24-yr period is found, with a maximum amplitude in the northwestern part of the basin (subpolar gyre and intergyre area). Its mechanism is as follows. In response to the wind stress forcing, anomalous currents appear between 35 degrees and 40 degrees N. They create temperature anomalies near the western coast, which are in turn advected by the mean current into the subpolar gyre and in the convection area. These temperature anomalies affect the thermohaline circulation, which produces new temperature anomalies near 35 degrees-40 degrees N and thus appears as a key component of this damped periodic mode. Wind stress forcing acts as efficiently as heat flux at exciting this oscillation, which can persist if external forcing is strong enough.