Seasonal Transport Variation in the Western Subtropical North Atlantic: Experiments with an Eddy-resolving Model

Böning, Claus W.; Döscher, Ralf; Budich, Reinhard

doi:10.1175/1520-0485(1991)021<1271:stvitw>2.0.co;2

Cited by 51 publications

(24 citation statements)

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“…This is in contrast to earlier work that envisaged a more asymmetric seasonal structure (e.g. Schott and Zantopp, 1985;Leaman et al, 1987;Schott et al, 1988;Lee and Williams, 1988;Greatbatch and Goulding, 1989;Rosenfeld et al, 1989;Boning et al, 1991;Fanning et al, 1994) or the possible emergence of a semi-annual like structure in the 1990s (Baringer and Larsen, 2001). Whilst some asymmetry of the long-term seasonal cycle is revealed by harmonic analysis, this asymmetry is marginal and the Florida Straits seasonal transport cycle is dominated by its annual component (Table 1).…”

Section: Emergence Of the Florida Straits Seasonal Transport Cycle Frcontrasting

confidence: 93%

“…Schott and Zantopp, 1985;Leaman et al, 1987;Schott et al, 1988;Lee and Williams, 1988;Mayer and Weisberg, 1993) in general agreement with model results (e.g. Anderson and Corry, 1985a;Rosenfeld et al, 1989;Greatbatch and Goulding, 1989;Boning et al, 1991;Fanning et al, 1994;Greatbatch et al, 1995). A significant fraction of variance at these periods has been linked to local meridional wind stress forcing in the Florida Straits, particularly at periods of days to tens of days where a barotropic response occurs (Lee and Williams, 1988).…”

Section: Introductionsupporting

confidence: 82%

“…In the absence of a plausible physical mechanism it is difficult to be convinced of the significance of apparent changes in seasonal cycle. Several authors have attributed the Florida Straits seasonal cycle to wind stress forcing in the vicinity of the Florida Straits Anderson and Corry, 1985a;Schott et al, 1988;Lee and Williams, 1988;Boning et al, 1991;Fanning et al, 1994) which shows similar seasonal phase to that of the Florida Straits transports. This is linked to the Florida Straits seasonal cycle through upstream wave propagation and local channel processes (e.g.…”

Section: Observations Of the Seasonal Cyclementioning

confidence: 90%

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On the seasonal cycles and variability of Florida Straits, Ekman and Sverdrup transports at 26° N in the Atlantic Ocean

et al. 2010

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Abstract.Since April 2004 the RAPID array has made continuous measurements of the Atlantic Meridional Overturning Circulation (AMOC) at 26 • N. Two key components of this system are Ekman transport zonally integrated across 26 • N and western boundary current transport in the Florida Straits. Whilst measurements of the AMOC as a whole are somewhat in their infancy, this study investigates what useful information can be extracted on the variability of the Ekman and Florida Straits transports using the decadal timeseries already available. Analysis is also presented for Sverdrup transports zonally integrated across 26 • N.The seasonal cycles of Florida Straits, Ekman and Sverdrup transports are quantified at 26 • N using harmonic analysis of annual and semi-annual constituents. Whilst Sverdrup transport shows clear semi-annual periodicity, calculations of seasonal Florida Straits and Ekman transports show substantial interannual variability due to contamination by variability at non-seasonal frequencies; the mean seasonal cycle for these transports only emerges from decadal length observations. The Florida Straits and Ekman mean seasonal cycles project on the AMOC with a combined peak-to-peak seasonal range of 3.5 Sv. The combined seasonal range for heat transport is 0.40 PW.The Florida Straits seasonal cycle possesses a smooth annual periodicity in contrast with previous studies suggesting a more asymmetric structure. No clear evidence is found to support significant changes in the Florida Straits seasonal cycle at sub-decadal periods. Whilst evidence of wind driven Florida Straits transport variability is seen at sub-seasonal and annual periods, a model run from the 1/4 • Correspondence to: C. P. Atkinson (christopher.atkinson@noc.soton.ac.uk) eddy-permitting ocean model NEMO is used to identify an important contribution from internal oceanic variability at sub-annual and interannual periods. The Ekman transport seasonal cycle possesses less symmetric structure, due in part to different seasonal transport regimes east and west of 50 to 60 • W. Around 60% of non-seasonal Ekman transport variability occurs in phase section-wide at 26 • N and is related to the NAO, whilst Sverdrup transport variability is more difficult to decompose.

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Section: Emergence Of the Florida Straits Seasonal Transport Cycle Frcontrasting

confidence: 93%

Section: Introductionsupporting

confidence: 82%

Section: Observations Of the Seasonal Cyclementioning

confidence: 90%

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On the seasonal cycles and variability of Florida Straits, Ekman and Sverdrup transports at 26° N in the Atlantic Ocean

et al. 2010

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“…Recent examples with realistic geometry and active thermodynamics are the U.S./German Community Modeling Effort (CME) for the North Atlantic [Bryan and Holland, 1989;Schott and Boning, 1991;Boning et al, 1991] and the U.K. Fine Resolution Antarctic Model [FRAM Group, 1991]. By employing a highly optimized ocean model, it is possible to approach the resolution of these regional models on a global basis.…”

Section: Introductionmentioning

confidence: 99%

Ocean general circulation from a global eddy‐resolving model

Semtner¹,

Chervin²

1992

J. Geophys. Res.

462

186

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A concerted effort has been made to simulate the global ocean circulation with resolved eddies, using a highly optimized model on the best available supercomputer. An earlier 20-year spin-up has been extended for 12.5 additional years: the first 2.5 with continued annual mean forcing and the final 10.0 with climatological monthly forcing. Model output archived at 3-day intervals has been analyzed into mean fields, standard deviations, products, and covariances on monthly, annual, and multiyear time scales. The multiyear results are examined here in order to give insight into the general circulation of the world ocean. The three-dimensional How fields of the model are quite realistic, even though resolution of eddies in high latitudes is marginal with a 0.5°, 20-level grid. The use of seasonal forcing improves the simulation, especially in the tropics and high northern latitudes. Mid-latitude gyre circulations, western boundary currents, zonal equatorial Hows, and the Antarctic Circumpolar Current (ACC) all show mean and eddy characteristics similar to those observed. There is also some indication of eddy intensification of the mean How of the ACC and of separated boundary jets. A global thermohaline circulation of North Atlantic Deep Water is identified in deep western boundary currents connected by the ACC. This deep circulation rises mainly in the equatorial Pacific. Several zonal jets are an integral part of this circulation near the equator. The deep How rises toward the surface in a series of switchbacks. Much of the thermohaline return How then follows an eddy-rich warm-water route through the Indonesian archipelago and around the southern tip of Africa. However, some intermediate level portions of the thermohaline circulation return south into the ACC and follow a cold water route through the Drake Passage. The representation of a global "conveyor belt" circulation with narrow and relatively high-speed currents along most of its path may be the most important result of this modeling study. Statistics of scalar fields such as transport stream function and surface height are exhibited, as are time series and frequency spectra of certain variables at selected points. These provide a baseline for comparison both with observations and with other model studies at higher resolution. Mean and eddy characteristics of the near-surface temperature and salinity fields are discussed, and surface forcing fields are examined. In particular, combined thermal and hydrological forcing effects are found to drive a conveyor belt circulation between the tropical Pacific and the high-latitude North Atlantic. The effect of weak restoring terms to observed temperature and salinity at great depth and in polar latitudes is found mainly to augment the model's convective processes, which are poorly resolved with 0.5° grid spacing. However, the deep restoring terms are insignificant in both the tropics and the mid-latitudes. The geographical distributions of eddy heat and salt transport are discussed. The eddies transport heat and sa...

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“…Though Fanning et al (1994) indicated that the meridional component of the wind stress is the most important for determining the model-calculated seasonal transport variations at the Florida Strait, they also indicated the importance of wind forcing to the north of 35°N in their model. On the other hand, Böning et al (1991) concluded that wind forcing north of 35°N is not important and wind forcing over the Caribbean/Florida Straits areas plays the major role for the seasonal transport variations at the Florida Straits. Fanning et al (1994) stated that the difference between both conclusions is associated with the difference of the dynamics included in both models.…”

Section: Case Bmentioning

confidence: 99%

Mechanism of the seasonal transport variation through the Tokara Strait

1995

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To investigate a mechanism of the seasonal variation of transport through the Tokara Strait, two numerical experiments with real geometry and wind forcing were carried out. The models are linear barotropic models which are a North Pacific Ocean model and a limited-area model with a fine grid. The seasonal variation of volume transport with a maximum in the summer and a minimum in the autumn could be well reproduced by both models. The results demonstrate the wind stress component normal to a gradient vector of bottom topography is crucial for determining the seasonal variation. The similar seasonal variation widely covers the East China Sea and has a large amplitude near the Tokara Strait. Finally, it can be concluded that winds north of 35°N have little influence on the seasonal response of our model at the Tokara Strait.

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Seasonal Transport Variation in the Western Subtropical North Atlantic: Experiments with an Eddy-resolving Model

Cited by 51 publications

References 0 publications

On the seasonal cycles and variability of Florida Straits, Ekman and Sverdrup transports at 26° N in the Atlantic Ocean

On the seasonal cycles and variability of Florida Straits, Ekman and Sverdrup transports at 26° N in the Atlantic Ocean

Ocean general circulation from a global eddy‐resolving model

Mechanism of the seasonal transport variation through the Tokara Strait

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