Open AccessObservations of Interannual Equatorial Freshwater Jets in the Western Pacific
Author(s) -
Xiaolin Zhang,
Allan J. Clarke
Publication year - 2015
Publication title -
journal of physical oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.706
H-Index - 143
eISSN - 1520-0485
pISSN - 0022-3670
DOI - 10.1175/jpo-d-14-0245.1
Subject(s) - zonal and meridional , geology , sea surface height , anomaly (physics) , climatology , sea surface temperature , atmosphere (unit) , meander (mathematics) , baroclinity , dynamic height , latitude , salinity , atmospheric sciences , oceanography , physics , geodesy , meteorology , hydrography , condensed matter physics , mathematics , geometry
Observations of TRITON moored array salinity and temperature in the very wet western equatorial Pacific at 137°E, 147°E, and 156°E since the late 1990s reveal the importance of rainfall to the interannual flow and El Niño–Southern Oscillation (ENSO) dynamics. Past work has shown that in this region a fresher surface isohaline layer is embedded in a thicker isothermal layer. Array estimates of dynamic height relative to the 50–70-m isothermal layer depth (ILD) indicate a near-surface salinity-driven contribution to the monthly sea level anomalythat is uncorrelated with, and smaller than, monthly anomalous sea surface height (SSH) estimated from altimeter data. Despite the smaller size of , its meridional gradient dominates the total sea level meridional gradient. Thus, the corresponding shallow equatorially trapped interannual freshwater jetdominates the near-surface zonal interannual flow. This jetlike flow has a meridional scale of only about 2°–3° of latitude, an amplitude of 23 cm s −1 , and is associated with the zonal back and forth displacement of the western equatorial warm/fresh pool that is fundamental to El Niño. The jet is not directly forced by the interannual freshwater surface flux but rather by wind stress anomalies that are mostly east of the warm/fresh pool edge during La Niña and mostly west of it during El Niño. A conceptual coupled ocean–atmosphere instability model is proposed to understand these observations. Calculations show that Aquarius satellite sea surface salinity (SSS) data match the TRITON in situ data well and that the satellite SSS can be used to estimate , and hence , geostrophically.