Low‐frequency spiciness variations in the tropical Pacific Ocean observed during 2003–2012

Abstract

Large‐scale spiciness variations in the Pacific Ocean during 2003–2012 are well recorded in the Argo‐based Grid Point Value of the Monthly Objective Analysis (MOAA GPV) dataset. Pronounced interannual spiciness anomalies between 25.0–25.5σθare detected near the outcropping areas in the eastern subtropics of both hemispheres. Differing from previous model results, the observed subtropical variations are more powerful in the North Pacific. While these subtropical signals diffuse quickly as propagating equatorward, large‐magnitude anomalies are generated in the off‐equatorial tropics (10°–14°N and 3°–7°S) under intensive current perturbation and further communicated to the central equatorial Pacific via interior‐ocean meridional flow. Although along‐equator signal propagation to the eastern Pacific upwelling zones is not discernable, appearance of spiciness anomalies leads to low‐frequency thermal variations in the central equatorial Pacific, which may play a role in the increasingly frequent occurrences of ENSO‐Modoki events.