A decadal spiciness mode in the tropics

Analysis of a complex climate model suggests the existence of a mode of coupled ocean- atmosphere variability in the tropical Pacific with the following dynamics; Anomalous strong Pacific trade winds accelerate the North Equatorial current and Countercurrent. At 10 degrees to 15 degrees N in the central Pacific thermocline this causes anomalous advection across mean gradients of temperature and salinity on isopycnal surfaces and generates cool/fresh spiciness anomalies of the order of 0.3 degrees K. These are advected by the mean circulation via the western boundary region to the equatorial Pacific in approximately five years. At the equatorial outcrops of the isopycnals, the cool/fresh anomalies affect the surface heat budget and are hypothesized to initiate a relaxation of the trade winds that is reinforced by positive feedbacks with the slope of the thermocline and with air-sea fluxes of heat and freshwater. At 5 degrees to 10 degrees S the decrease of the trades generates by anomalous advection cool/fresh spiciness anomalies that migrate to the equator in one to two years and provide a positive feedback. At 10 degrees to 15 degrees N, the decrease of the trades decelerates North Equatorial current and Countercurrent and causes warm/salty anomalies on isopycnals that arrive at the equator five years later and close the cycle.