Western Boundary Currents

Imawaki, Shiro; Bower, Amy S.; Beal, Lisa M.; Qiu, Bo

doi:10.1016/b978-0-12-391851-2.00013-1

Cited by 54 publications

(43 citation statements)

References 287 publications

(265 reference statements)

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“…The western boundary current system of the South Atlantic Ocean, including the collision of the subtropical and subantarctic western boundary currents and the eddy field generated after the collision, is known as the Brazil‐Malvinas Confluence (BMC) [e.g., Matano et al ., ; Stramma and England , ; Imawaki et al ., ]. It is an energetic region with turbulence on multiple scales [ Fu , ; Lumpkin and Garzoli , ; Venaille et al ., ; Lumpkin and Johnson , ; Strub et al ., ].…”

Section: Introductionmentioning

confidence: 99%

Subregional characterization of mesoscale eddies across the Brazil‐Malvinas Confluence

et al. 2017

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Horizontal and vertical motions associated with coherent mesoscale structures, including eddies and meanders, are responsible for significant global transports of many properties, including heat and mass. Mesoscale vertical fluxes also influence upper ocean biological productivity by mediating the supply of nutrients into the euphotic layer, with potential impacts on the global carbon cycle. The Brazil‐Malvinas Confluence (BMC) is a western boundary current region in the South Atlantic with intense mesoscale activity. This region has an active role in the genesis and transformation of water masses and thus is a critical component of the Atlantic meridional overturning circulation. The collision between the Malvinas and Brazil Currents over the Patagonian shelf/slope creates an energetic front that translates offshore to form a vigorous eddy field. Recent improvements in gridded altimetric sea level anomaly fields allow us to track BMC mesoscale eddies with high spatial and temporal resolutions using an automated eddy tracker. We characterize the eddies across fourteen 5° × 5° subregions. Eddy‐centric composites of tracers and geostrophic currents diagnosed from a global reanalysis of surface and in situ data reveal substantial subregional heterogeneity. The in situ data are also used to compute the evolving quasi‐geostrophic vertical velocity (QG‐ω) associated with each instantaneous eddy instance. The QG‐ω eddy composites have the expected dipole patterns of alternating upwelling/downwelling, however, the magnitude and sign of azimuthally averaged vertical velocity varies among subregions. Maximum eddy values are found near fronts and sharp topographic gradients. In comparison with regional eddy composites, subregional composites provide refined information about mesoscale eddy heterogeneity.

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Section: Introductionmentioning

confidence: 99%

Subregional characterization of mesoscale eddies across the Brazil‐Malvinas Confluence

et al. 2017

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“…Each WBC in an oceanic subtropical gyre has a similar jetlike velocity structure as it flows along its continental boundary. Each WBC is approximately 100 km in width (80-150 km is the typical range) and 1,000 m in vertical extent (typical distance from the sea surface to the 0.2 m s −1 isotach), and each transports approximately 30-100 sverdrups (Sv) of seawater (1 Sv = 10 6 m 3 s −1 ) (Imawaki et al 2013). The downstream current speed is strongest at the surface near the center of the current (the surface-speed maximum is usually located somewhat to the shoreward side of the geometric center of the current jet), and the speed decreases in any direction away from the surface maximum.…”

Section: Jetlike Flow In Western Boundary Currentsmentioning

confidence: 99%

“…Each profile is a synoptic instantaneous snapshot (as opposed to a long-term average) and has its speed maximum positioned at 80 km on the horizontal axis to more clearly show the similarity in the jetlike profiles. Two common types of lateral WBC motions are propagating, wavelike meanders of the path of the current and lateral path shifts (Hogg & Johns 1995, Lee & Cornillon 1995, Imawaki et al 2013. WBC meanders typically have periods of a few days to a few weeks, and path shifts can move a long stretch of the current laterally to a new position, where it may remain for weeks to months.…”

Section: Maximum Speedmentioning

confidence: 99%

Marine Hydrokinetic Energy from Western Boundary Currents

Bane

Muglia

et al. 2017

Annu. Rev. Mar. Sci.

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The kinetic energy in ocean currents, or marine hydrokinetic (MHK) energy, is a renewable energy resource that can help meet global energy requirements. An ocean circulation model-based census shows that subtropical surface western boundary currents (WBCs) are the only nearshore, large-scale currents swift enough to drive large electricity-generating ocean turbines envisioned for future use. We review several WBCs in the context of kinetic energy extraction. The power density in the Gulf Stream off North Carolina at times reaches several thousand watts per square meter at 75 m below the surface, and the annual average power is approximately 500-1,000 W m −2 . Significant fluctuations occur with periods of 3-20 days (Gulf Stream meanders) and weeks to months (Gulf Stream path shifts). Interannual variations in annual average power occur because of year-to-year changes in these WBC motions. No large-scale turbines presently exist, and the road to establishing MHK facilities in WBCs will encounter challenges that are similar in many aspects to those associated with the development of offshore wind power.

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“…The Gulf Stream, like most WBCs, is a narrow (∼100 km in width), deep (∼1 km in vertical extent) jetlike flow that has a maximum surface-current speed often in excess of 2 m s −1 (Imawaki et al 2013). Current speed decreases in any direction away from this surface maximum.…”

Section: The Gulf Streammentioning

confidence: 99%

Marine Renewable Energy

Yang¹,

Copping²

2017

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Western Boundary Currents

Cited by 54 publications

References 287 publications

Subregional characterization of mesoscale eddies across the Brazil‐Malvinas Confluence

Subregional characterization of mesoscale eddies across the Brazil‐Malvinas Confluence

Marine Hydrokinetic Energy from Western Boundary Currents

Marine Renewable Energy

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