Pacific Equatorial Subsurface Countercurrent Velocity, Transport, and Potential Vorticity*

Rowe, Glen; Firing, Eric; Johnson, Gregory C.

doi:10.1175/1520-0485(2000)030<1172:pescvt>2.0.co;2

Cited by 74 publications

(130 citation statements)

References 15 publications

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“…Culture experiments and surface-sediment samples indicate temperature as one of the major environmental parameters affecting the foraminiferal biogeographic distribution (Bé and Tolderlund, 1971;Bijma et al, 1990;Morey et al, 2005). Even though most planktonic foraminifera Tomczak and Godfrey, 1994;Firing et al, 1998;Rowe et al, 2000). (b) Longitudinal depth section of annual nitrate along 3°S (see dashed line in (a)) with multinet position SO225-21-3 (black vertical line).…”

Section: Foraminiferal Ecological Preferences and Hydrographic Settingmentioning

confidence: 99%

“…Through a complex and highly dynamic current system (e.g., Wyrtki and Kilonski, 1984;Fine et al, 1994;Tomczak and Godfrey, 1994;Johnson and Moore, 1997;Rowe et al, 2000;Goodman et al, 2005;Grenier et al, 2011), including the South Equatorial Current (SEC), the persistent eastward-directed subsurface Equatorial Undercurrent (EUC) and the Tsuchiya Jets (after Tsuchiya, 1972), nutrients are transported via intermediate and mode waters from the extratropical HNLC regions to the thermocline of the Western Equatorial Pacific and upwell along the equator in the Pacific equatorial divergence.…”

Section: Foraminiferal Ecological Preferences and Hydrographic Settingmentioning

confidence: 99%

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Constraining foraminiferal calcification depths in the western Pacific warm pool

Rippert

Nürnberg

Raddatz

et al. 2016

Marine Micropaleontology

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Insight into past changes of upper ocean stratification, circulation, and nutrient signatures rely on our knowledge of the apparent calcification depth (ACD) and ecology of planktonic foraminifera, which serve as archives for paleoceanographic relevant geochemical signals. The ACD of different species varies strongly between ocean basins, but also regionally. We constrained foraminiferal ACDs in the Western Pacific Warm Pool (Manihiki Plateau) by comparing stable oxygen and carbon isotopes (δ 18 O calite , δ 13 C calcite ) as well as Mg/Ca ratios from living planktonic foraminifera to in-situ physical and chemical water mass properties (temperature, salinity, δ 18 O seawater , δ 13 C DIC ). Our analyses point to Globigerinoides ruber as the shallowest dweller, followed by Globigerinoides sacculifer, Neogloboquadrina dutertrei, Pulleniatina obliquiloculata and Globorotaloides hexagonus inhabiting increasing greater depths. These findings are consistent with other ocean basins; however, absolute ACDs differ from other studies. The uppermost mixed-layer species G. ruber and G. sacculifer denote mean calcification depths of~95 m and~120 m, respectively. These Western Pacific ACDs are much deeper than in most other studies and most likely relate to the thick surface mixed layer and the deep chlorophyll maximum in this region. Our results indicate that N. dutertrei appears to be influenced by mixing waters from the Pacific equatorial divergence, while P. obliquiloculata with an ACD of~160 m is more suitable for thermocline reconstructions. ACDs of G. hexagonus reveal a deep calcification depth of~450 m in oxygen-depleted, but nutrient-rich water masses, consistent to other studies. As the δ 13 C of G. hexagonus is in near-equilibrium with ambient seawater, we suggest this species is suitable for tracing nutrient conditions in equatorial water masses originating in extra-topical regions.

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Section: Foraminiferal Ecological Preferences and Hydrographic Settingmentioning

confidence: 99%

Section: Foraminiferal Ecological Preferences and Hydrographic Settingmentioning

confidence: 99%

Constraining foraminiferal calcification depths in the western Pacific warm pool

Rippert

Nürnberg

Raddatz

et al. 2016

Marine Micropaleontology

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“…AAIW has its origin in the subduction of polar surface waters (see, e.g., Molinelli 1978) and spreads at the base of the subtropical gyres, at depths between 600 and 1000 m. However, with a core density anomaly of about 27.2 kg m Ϫ3 , AAIW lies below the water that upwells along the Pacific equator. Upwelling along the Pacific equator is, rather, fed in the density range of waters advected in the Equatorial Undercurrent (EUC) and the subsurface countercurrents (SCC) (Rowe et al 2000), the subsurface pathways from west to east (and deep and shallow) along the equator. The equatorial Pacific is fed by about 60% from the SP.…”

Section: Introductionmentioning

confidence: 99%

Formation of the South Pacific Shallow Salinity Minimum: A Southern Ocean Pathway to the Tropical Pacific

Karstensen

2004

Journal of Physical Oceanography

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In the eastern South Pacific Ocean, at a depth of about 200 m, a salinity minimum is found. This minimum is associated with a particular water mass, the ''Shallow Salinity Minimum Water'' (SSMW). SSMW outcrops in a fresh tongue (S min ) centered at about 45ЊS. The S min appears to emanate from the eastern boundary, against the mean flow. The watermass transformation that creates SSMW and S min is investigated here. The S min and SSMW are transformed from saltier and warmer waters originating from the western South Pacific. The freshening and cooling occur when the water is advected eastward at the poleward side of the subtropical gyre. Sources of freshening and cooling are air-sea exchange and advection of water from south of the subtropical gyre. A freshwater and heat budget for the mixed layer reveals that both sources equally contribute to the watermass transformation in the mixed layer. The freshened and cooled mixed layer water is subducted into the gyre interior along the southern rim of the subtropical gyre. Subduction into the zonal flow restricts the transformation of interior properties to diffusion only. A simple advection/diffusion balance reveals diffusion coefficients of order 2000 m 2 s Ϫ1 . The tongue shape of the S min is explained from a dynamical viewpoint because no relation to a positive precipitation-evaporation balance was found. Freshest S min values are found to coincide with slowest eastward mixed layer flow that accumulates the largest amounts of freshwater in the mixed layer and creates the fresh tongue at the sea surface. Although the SSMW is the densest and freshest mode of water subducted along the South American coast, the freshening and cooling in the South Pacific affect a whole range of densities (25.0-26.8 kg m Ϫ3 ). The transformed water turns northward with the gyre circulation and contributes to the hydrographic structure of the gyre farther north. Because the South Pacific provides most of the source waters that upwell along the equatorial Pacific, variability in South Pacific hydrography may influence equatorial Pacific hydrography. Because one-half of the transformation is found to be controlled through Ekman transport, variability in wind forcing at the southern rim of the subtropical gyre may be a source for variability of the equatorial Pacific.

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“…Based on a detailed analysis of the subsurface temperature data and surface winds, Kessler (2002Kessler ( , 2006 concluded that a substantial portion of the NECC divides and flows westward into the NEC and SEC ;2000 mi (1 mi ' 1.6 km) from the Central American coast, while the upper ocean east of 1158W has a different circulation regime driven by the regional winds. A portion of the cold water that local winds cause to upwell in the Costa Rica Dome is supplied by the eastward ''Tsuchia jet,'' which is located at about 150-m depth and 68N in the eastern Pacific (Rowe et al 2000;Kessler 2002;Furue et al 2009). While wind-driven linear ocean dynamics appears to explain much of the mean annual cycle of the upper-ocean circulation in the NETP, nonlinear eddies generated by strong currents near the coast may also contribute to the seasonal evolution of the Costa Rica Dome (Umatani and Yamagata 1991).…”

mentioning

confidence: 99%

ENSO’s Impact on the Gap Wind Regions of the Eastern Tropical Pacific Ocean*

et al. 2012

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The recently released NCEP Climate Forecast System Reanalysis (CFSR) is used to examine the response to ENSO in the northeast tropical Pacific Ocean (NETP) during 1979-2009. The normally cool Pacific sea surface temperatures (SSTs) associated with wind jets through the gaps in the Central American mountains at Tehuantepec, Papagayo, and Panama are substantially warmer (colder) than the surrounding ocean during El Niñ o (La Niñ a) events. Ocean dynamics generate the ENSO-related SST anomalies in the gap wind regions as the surface fluxes damp the SSTs anomalies, while the Ekman heat transport is generally in quadrature with the anomalies. The ENSO-driven warming is associated with large-scale deepening of the thermocline; with the cold thermocline water at greater depths during El Niñ o in the NETP, it is less likely to be vertically mixed to the surface, particularly in the gap wind regions where the thermocline is normally very close to the surface. The thermocline deepening is enhanced to the south of the Costa Rica Dome in the Papagayo region, which contributes to the local ENSO-driven SST anomalies. The NETP thermocline changes are due to coastal Kelvin waves that initiate westward-propagating Rossby waves, and possibly ocean eddies, rather than by local Ekman pumping. These findings were confirmed with regional ocean model experiments: only integrations that included interannually varying ocean boundary conditions were able to simulate the thermocline deepening and localized warming in the NETP during El Niñ o events; the simulation with variable surface fluxes, but boundary conditions that repeated the seasonal cycle, did not.

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Pacific Equatorial Subsurface Countercurrent Velocity, Transport, and Potential Vorticity*

Cited by 74 publications

References 15 publications

Constraining foraminiferal calcification depths in the western Pacific warm pool

Constraining foraminiferal calcification depths in the western Pacific warm pool

Formation of the South Pacific Shallow Salinity Minimum: A Southern Ocean Pathway to the Tropical Pacific

ENSO’s Impact on the Gap Wind Regions of the Eastern Tropical Pacific Ocean*

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