The mixing process results in a salinity minimum and also in rejuvenation of the NPIW layer in the subtropical gyre due to the Oyashio input.
[1][2] The NPIW occurs where the cold, low-saline Oyashio and warm, saline Kuroshio currents meet.
The Oyashio water is freshened in the Okhotsk Sea and transported to the North Pacific subtropical gyre by thermohaline circulation.
The low salinity and high oxygen at the density of the NPIW are attained in the subpolar gyre, through vertical diffusion in the open North Pacific and direct ventilation in the Okhotsk Sea as a result of sea ice formation.
According to recent studies, the NPIW is formed along three paths between the Kuroshio Extension and the subarctic front.