The Characteristics of Near‐Equatorial North Pacific Low PV Water and Its Possible Influences on the Equatorial Subsurface Ocean

Abstract

AbstractUsing SODA oceanic reanalysis data, the subduction rate and low potential vorticity (PV) water masses in the North Pacific are investigated from January 1870 to December 2008. A new low PV water mass with a large subduction rate is found near‐equatorial North Pacific, which is named as the near‐equatorial North Pacific low PV water mass (NELPVW), and it is the only one low PV water mass in North Pacific that appears an increasing trend under global warming. Among all the low PV water masses in North Pacific, only Eastern Subtropical Mode Water (EMW) and NELPVW can migrate to the equatorial Pacific and effect subsurface oceanic temperature (SOT) there. Further research shows that the subducted low PV water mass in EMW generation region can migrate to equatorial Pacific through two transport paths, which are called the Western‐EMW path and the Central‐EMW path. The analysis of Lagrange tracking shows that EMW can migrate and bring SOT anomaly to equatorial Pacific along these paths in 7 years and lead to the almost precisely opposite distributions of equatorial Pacific SOT anomaly between the strong and weak EMW subduction years, while it takes the newly discovered NELPVW less than 3 years to reach the equatorial Pacific along the Western‐NELPVW path or the Eastern‐NELPVW path after subduction. The distributions of equatorial Pacific SOT anomaly in the strong and weak NELPVW subduction years are approximately reverse too. The actual distribution of the equatorial Pacific SOT is affected by these two low PV water masses at the same time.