Oral

IAMAS

JMP05 - Variability and change in Pacific Ocean-Atmosphere system

Extreme Ventilation of the North Pacific Central Mode Water by El Nino During Positive Phase of the Pacific Decadal Oscillation

The North Pacific Central Mode Water (CMW) is a vertically homogeneous thermocline water mass in the central North Pacific, affecting the subtropical gyre's large-scale circulation and the storage of heat and carbon. Previous studies mainly focus on the CMW variability forced by Pacific Decadal Oscillation (PDO), without considering the relative phase of the El Ni?o-Southern Oscillation (ENSO). The present study finds that the interannual variability of CMW is significantly related to the ENSO-PDO phase relationship. For in-phase conditions, the CMW is strongest in the decay year of El Ni?o during positive PDO, and the CMW is weakest in the decay year of La Ni?a during negative PDO. For out-of-phase conditions, by contrast, the CMW variation is moderate. After El Ni?o winter during positive PDO, the strongest surface buoyancy loss sharply deepens the mixed layer and injects well-mixed surface water into the thermocline in the central North Pacific east of the dateline, where no such "ventilation" occurs for other cases. The extreme CMW ventilation favors the transport of anthropogenic heat, carbon, oxygen & nutrient rich waters into the deep ocean, important for the climate system.