Circulation and water mass transformation as related to the formation of subtropical mode water in the North Pacific

The processes which create and distribute subtropical mode water (STMW) in the North Pacific are studied using both data and analytical techniques.;STMW is placed within the larger circulation of the northwestern subtropical gyre. Analysis of the Levitus data shows a pattern of different STMW layers being spread in different directions by the ambient circulation.;The distribution of STMW at its outcrop in winter is studied using XBT data from the TRANSPAC program. The data are averaged in three-dimensional "stream coordinates" which use the Kuroshio as a reference. The average shows isotherms crossing the Kuroshio and then abruptly leaving it at certain points. This structure is confirmed by looking at XBT data from one particular month.;Cooling is shown to be an essential part of STMW formation. Stream lines of geopotential anomaly at the surface turn to the right with depth, in the direction of the cooling spiral of Schott and Stommel (1978). The picture of isotherms crossing the Kuroshio front combined with what is known about the velocity structure of the along-stream flow suggest that cooling at the surface is stronger and more intensified at the core of the Kuroshio than previously thought. The distribution of mixed layer thickness in the stream coordinate system is used to demonstrate that the advection of relative vorticity is unimportant in the vorticity balance of forming STMW.;Data from a series of sections along 137;A simple, two-layer, quasi-geostrophic model shows that the primary vorticity balance in the Kuroshio is the input of low potential vorticity from cooling balanced by stretching of the water column.;An inverse calculation of Kuroshio transport in the East China Sea is done using two CTD sections across the Kuroshio. The calculated transports are 26.6...