The pathway and circulation of North Pacific Intermediate Water

Abstract

It has been speculated that the subtropical North Pacific Intermediate Water (NPIW) was formed by a shortcut of Okhotsk Sea source into the western subtropical gyre because this is the geographically shortest distance, and based on incomplete data. This mechanism is contradictory to the distribution of seawater properties, and, dynamically, is inconsistent with a basin‐wide distribution of NPIW and associated gyre circulation. A lengthy transpacific pathway has been identified for the transformed NPIW source waters that first enter the eastern subtropical gyre, which is robust in a water‐mass age distribution. Using an updated hydrography and a water‐mass mixing scheme combining property distribution with flow streamfunction the present study establishes a dynamically self‐consistent gyre circulation of NPIW and its pathway from the subpolar formation regions (source) to the Indonesian Throughflow (sink).