Impact of Sea Level Assimilation on Salinity Variability in the Western Equatorial Pacific

Abstract Upper-ocean salinity variation in the tropical Pacific is investigated during the 2000s, when Triangle Trans-Ocean Buoy Network (TRITON) buoys and Argo floats were deployed and more salinity data were observed than in previous periods. This study focuses on upper-ocean salinity variability during the warming period of El Niño–Southern Oscillation (ENSO)-like quasi-decadal (QD)-scale sea surface temperature anomalies over the central equatorial Pacific (January 2002–December 2005; hereafter “warm QD phase”). It is shown that strong negative salinity anomalies occur in the western tropical Pacific and the off-equatorial Pacific in the upper ocean at depths less than 80 m, showing a horseshoe-like pattern centered at the western tropical Pacific during the warm QD phase. TRITON mooring buoy data in the western equatorial Pacific show that low-salinity and high-temperature water could be transported eastward from the western equatorial Pacific to the central equatorial Pacific during the warm QD phase. Similar patterns, but with the opposite sign of salinity anomalies, appear in the cold QD phase during January 2007–December 2009 with negative sea surface temperature anomalies over the central equatorial Pacific. It is suggested that effects from zonal salinity advection and precipitation could contribute to the generation of the salinity variations in the western equatorial Pacific for QD phases during the 2000s. On the other hand, the contribution of meridional salinity advection is much less than that of zonal salinity advection. In addition, El Niño Modoki and La Niña events could affect salinity changes for warm and cold QD phases via interannual-scale zonal salinity advection variations in the western equatorial Pacific during the 2000s.

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The 20°C isotherm depth and sea level in the western equatorial pacific

Journal of Engineering Physics and Thermophysics ◽

10.1007/bf02309057 ◽

1981 ◽

Vol 37 (4) ◽

pp. 198-200 ◽

Cited By ~ 11

Author(s):

Masaaki Chaen ◽

Klaus Wyrtki

Keyword(s):

Sea Level ◽

Equatorial Pacific ◽

Western Equatorial Pacific ◽

And Sea Level

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Salinity Interdecadal Variability in the Western Equatorial Pacific and Its Effects During 1942-2018

10.21203/rs.3.rs-832621/v1 ◽

2021 ◽

Author(s):

Rong-Hua Zhang ◽

Guanghui Zhou ◽

Hai Zhi ◽

Chuan Gao ◽

Hongna Wang ◽

...

Keyword(s):

Ensemble Empirical Mode Decomposition ◽

Equatorial Pacific ◽

Ocean Reanalysis ◽

Surface Warming ◽

Salinity Effects ◽

Mode Decomposition ◽

Salinity Variability ◽

Western Equatorial Pacific ◽

Subsurface Layers ◽

Eemd Method

Abstract Ocean reanalysis products are used to examine salinity variability and its relationships with temperature in the western equatorial Pacific during 1942-2018. An ensemble empirical mode decomposition (EEMD) method is adopted to separate salinity and temperature signals at different time scales; a focus is placed on interdecadal component in this study. Pronounced interdecadal variations in salinity are seen in the western equatorial Pacific, which exhibits persistent and transitional phases in association with temperature. A surface freshening is accompanied by a surface warming during the 1980s-1990s, but saltening and cooling in the 2000s, with interdecadal shifts occurring around the late 1970s, late 1990s, and in 2016-2018, respectively. Determined by anomaly signs of temperature and salinity, their combined effects can be density-compensated or density-uncompensated, acting to produce density variability that is suppressed or enhanced, respectively. The effects are phase- and region dependent. In the subsurface layers at 200m, where salinity and temperature anomalies are nearly of the same sign during interdecadal evolution, their effects are mostly density-compensated. The situation is more complicated in the surface layer. Variations in SSS and SST during the persistent phases tend to be of opposite sign with their density-uncompensated effects, acting to enhance density anomalies; but they can be of the same sign during the transitional periods, with density-compensated salinity effects. Examples are given for relationships among these fields which exhibit phase differences in anomaly transitions in the late 1990s in the western equatorial Pacific; salinity anomalies are seen to cause a delay in phase transition of density anomalies. Furthermore, their relative contributions to interdecadal variabilities of density and stratification are quantified. The consequences for salinity effects are also discussed with their feedbacks on local SST.

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Open-ocean validation of TOPEX/POSEIDON sea level in the western equatorial Pacific

Journal of Geophysical Research Atmospheres ◽

10.1029/95jc02128 ◽

1995 ◽

Vol 100 (C12) ◽

pp. 25109 ◽

Cited By ~ 32

Author(s):

Joël Picaut ◽

Antonio J. Busalacchi ◽

Michael J. McPhaden ◽

Lionel Gourdeau ◽

Frank I. Gonzalez ◽

...

Keyword(s):

Sea Level ◽

Equatorial Pacific ◽

Open Ocean ◽

Western Equatorial Pacific

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On the Joint Role of Subtropical Atmospheric Variability and Equatorial Subsurface Heat Content Anomalies in Initiating the Onset of ENSO Events

Journal of Climate ◽

10.1175/jcli4075.1 ◽

2007 ◽

Vol 20 (8) ◽

pp. 1593-1599 ◽

Cited By ~ 35

Author(s):

Bruce T. Anderson

Keyword(s):

Sea Level ◽

North Pacific ◽

Heat Content ◽

Equatorial Pacific ◽

Boreal Winter ◽

Sea Level Pressure ◽

Level Pressure ◽

Enso Events ◽

Western Equatorial Pacific ◽

Central North Pacific

Abstract Previous research has shown that seasonal mean variations in both the subtropical/extratropical sea level pressures over the central North Pacific and the subsurface heat content anomalies in the western equatorial Pacific are significantly related to the state of the El Niño–Southern Oscillation (ENSO) 12–18 months later. Here we find that positive (negative) subsurface temperature anomalies in the western equatorial Pacific during boreal summer/fall, followed by negative (positive) anomalies in the sea level pressure fields over the subtropical central North Pacific during boreal winter, tend to result in positive (negative) mature ENSO events 12–15 months later (i.e., during the following boreal winter). When the intervening sea level pressure anomalies are of the same sign as the preceding heat-content anomalies, the correlation between the heat-content anomalies and the following boreal-winter ENSO state disappears. There is still some relation between the boreal-winter sea level pressure anomalies and the ENSO state the following year when the two precursor patterns are of the same sign; however, the correlation is smaller and the ENSO events tend to be weaker. Additional analysis indicates that the two precursor fields are related to one another; however, the sea level pressure variations contain more unique information about, and provide better predictability of, the state of the following ENSO system than do the heat content anomalies.

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Oxygen minimum expansion in the Sulu Sea, western equatorial Pacific, during the last glacial low stand of sea level

Marine Micropaleontology ◽

10.1016/0377-8398(85)90008-8 ◽

1985 ◽

Vol 9 (5) ◽

pp. 395-418 ◽

Cited By ~ 42

Author(s):

Braddock K. Linsley ◽

Robert C. Thunell ◽

Carol Morgan ◽

Douglas F. Williams

Keyword(s):

Sea Level ◽

Equatorial Pacific ◽

Sulu Sea ◽

Last Glacial ◽

Western Equatorial Pacific ◽

Oxygen Minimum ◽

The Last Glacial

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Coastline Direction, Interannual Flow, and the Strong El Niño Currents along Australia's Nearly Zonal Southern Coast

Journal of Physical Oceanography ◽

10.1175/jpo2645.1 ◽

2004 ◽

Vol 34 (11) ◽

pp. 2373-2381 ◽

Cited By ~ 26

Author(s):

Jianke Li ◽

Allan J. Clarke

Keyword(s):

Sea Level ◽

El Niño ◽

El Nino ◽

Low Frequency ◽

Equatorial Pacific ◽

Shelf Edge ◽

Southern Coast ◽

Equatorial Pacific Ocean ◽

Western Equatorial Pacific ◽

Coastal Sea

Abstract The western equatorial Pacific Ocean El Niño signal leaks through the gappy western equatorial Pacific Ocean boundary to the western and southern coasts of Australia. Ocean Topography Experiment (TOPEX)/Poseidon sea level data and coastal tide gauge measurements show that off the northwest coast the low-frequency signal propagates westward as large-scale Rossby waves. However, along the nearly zonal southern coast, particle displacements are nearly zonal near the coast and experience no planetary vorticity change. As a consequence, the Rossby wave mechanism fails, and theory suggests that the signal should decay from the shelf edge with baroclinic Rossby radius-of-deformation scale. High-resolution along-track TOPEX/Poseidon sea level heights show that the interannual height signal does decay rapidly seaward of the shelf edge with this scale. The sharp fall in sea level and geostrophic balance imply strong (∼10 cm s−1) low-frequency currents seaward of the shelf edge. On the shelf, interannual flow is in the same direction as the shelf-edge flow but is much weaker. The anomalous flows tend to be eastward during La Niña, when the western equatorial Pacific and Australian coastal sea levels are unusually high, and westward during El Niño when coastal sea levels tend to be anomalously low. The anomalous low-frequency flows can transport larvae large distances, enhancing the recruitment of Australian salmon to nursery grounds in the eastern part of the southern coast when the coastal sea level is higher than normal and decreasing recruitment when it is lower than normal.

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