Seasonal Modulation of Dissolved Oxygen in the Equatorial Pacific by
Tropical Instability Vortices
Abstract
Tropical Instability Vortices (TIVs) have a major influence on the
physics and biogeochemistry of the equatorial Pacific. Using an
eddy-resolving configuration of the Community Earth System Model
(CESM-HR) and Lagrangian particle tracking, we examine TIV impacts on
the three-dimensional structure and variability of dissolved oxygen (O2)
in the upper equatorial Pacific water column. In CESM-HR, the simulated
generation and westward propagation of TIVs from boreal summer through
winter lead to the seasonal oxygenation of the upper northern equatorial
Pacific, exhibited as a deepening of hypoxic depth west of 120ºW. TIV
effects on the equatorial Pacific oxygen balance are dominated by
eddy-advection and mixing, while indirect TIV effects on O2 consumption
play minor roles. These advective effects reflect the transient
displacements of isopycnals by eddy pumping as well as vortex transport
of oxygen by eddy trapping, stirring, and subduction. TIVs influence on
the upper equatorial Pacific O2 distribution and variability has
important implications for understanding and modeling marine ecosystem
dynamics and habitats, and should be taken into consideration in
designing observation networks in this region.