Ocean Gyres — Sverdrup Balance

Wind-driven circulation with western boundary current intensification (Stommel model)

Wind Stress (τ) 1.0×

Bottom Friction (r) 0.5

β (PV gradient) 1.0

Warm current (Gulf Stream/Kuroshio) Cool return flow Wind curl forcing

The Stommel (1948) model: β-effect creates asymmetric gyres — eastern side is broad and slow (Sverdrup interior), western side is narrow and fast (Gulf Stream, Kuroshio). Western boundary current width ∝ r/β. Curl of wind stress drives vertical motion via Ekman pumping, setting the gyre's streamfunction.