VENTILATION OF THE SUBTROPICAL NORTH PACIFIC

The ventilation of the subtropical North Pacific is studied using a si mple analytical model. The model is forced by winter mixed layer densi ty and depth calculated from the Levitus climatology and wind stress c url from the Hellerman and Rosenstein wind stress data. The wind-drive n gyre in the North Pacific is shallow, no more than 1.4 km. The gross feature of the subduction rate is very similar to the results by Huan g and Qiu based on data analysis of the Levitus climatology, with a to tal ventilation rate of 31.3 Sv (Sv drop 10(6) m(3) s(-1)), including 20.8 Sv due to the vertical pumping and 10.5 Sv due to lateral inducti on. The age of water within the ventilated thermocline is relatively y oung, it is no more than 10 years old, except near the southeast corne r of the basin. The young age indicates a fast communication between t he atmosphere and the upper ocean on a timescale of less than 10 years . The vertical mass partition is slightly different from the results b ased on analyzing climatology by Huang and Qiu. Most importantly, the total mass flux in the unventilated thermocline is about 28.3 Sv, smal ler than the 31.3 Sv obtained by analyzing the climatology.