Collision of boundary currents: beyond a steady state

Lebedev, Ivan; Nof, Doron

doi:10.1016/s0967-0637(96)00127-6

Cited by 10 publications

(3 citation statements)

References 19 publications

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“…These observations are corroborated by Witter and Gordon [1999] altimeter‐derived surface geostrophic velocities, in which a gradual decrease in the strength of the MC between 1993 and mid‐1995 is observed, followed by an increase in its strength through early 1997. As pointed out by Lebedev and Nof [1997], this supports the idea that the variability of the BMC can be partly dictated by variations in the MC transport through upstream propagating Kelvin waves. When the distance between these two opposing flows is relatively small, less rings are shed and the BC meridional time mean latitude of separation becomes dependent on the MC upstream behavior.…”

Section: Summary and Discussionsupporting

confidence: 81%

Statistics of Brazil Current rings observed from AVHRR: 1993 to 1998

Lentini¹,

Olson²,

Podesta³

2002

Geophysical Research Letters

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[1] A 6-year time series of sea surface temperature fields derived from NOAA polar-orbiter AVHRR 5-day composites is used to estimate the lifetime, size, and trajectory of 43 warm-core rings shed by the Brazil Current at the Southwestern Atlantic region in a consistent fashion for the first time. Ring lifetimes range from 11 to 95 days, and are not bi-modal as is the case for the Gulf Stream anticyclones. Translational speeds range from 4.2 to 27.2 km/day with a mean value of 13.1 km/day. After formation, rings are mostly elliptical with a mean major radius of 126 ± 50 km and a minor radius of 65 ± 22 km. None of the rings seem to last more than four months in the region. An attempt to explore possible connections between ring shedding variability and the Antarctic Dipole is also addressed.

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Section: Summary and Discussionsupporting

confidence: 81%

Statistics of Brazil Current rings observed from AVHRR: 1993 to 1998

Lentini¹,

Olson²,

Podesta³

2002

Geophysical Research Letters

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“…The significant energetic peaks in a 30-110-day period band found in the MC transport at 41°S and in the velocity time series associated with the subducted inner branch of the MC at 37°S (Artana et al, 2019) could be associated with TW. Theoretical works also suggested that TW could affect the position of the encounter of the Brazil and Malvinas Current (Lebedev & Nof, 1997). (V(x, z)), for a given frequency and wavenumber.…”

Section: Summary and Discussionmentioning

confidence: 99%

Anatomy of Subinertial Waves Along the Patagonian Shelf Break in a 1/12° Global Operational Model

et al. 2020

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The Malvinas Current (MC), a major western boundary current of the South Atlantic Ocean, is an offshoot of the Antarctic Circumpolar Current (Figure 1a) that flows northward following the Subantarctic Front (SAF) along the eastern continental slope of South America. The MC, which borders one of the widest continental shelves of the world, is strongly controlled by bottom topography. Between 52°S and 49°S, the bottom slope is west-east orientated and gentle (2,000 m over 300 km) and the MC is rather wide (300 km) with mean northward surface velocities of 30 cm/s (Figures 1a and 1b). At 48°S, isobaths are east-west orientated and the MC mean surface velocities are zonal with a mean value of 40 cm/s. The largest mean surface velocities in the MC (>60 cm/s) are observed north of 43°S where the bottom slope is steep (Figures 1a and 1b) and the MC is organized in one narrow jet. South of 43°S, the MC is characterized by a relatively stable two-jet structure alienated with two bottom terraces (Piola et al., 2013). The mean location of the onshore jet corresponds to a northern branch of the SAF (SAF-N), while the main jet follows the main SAF along the 1,500-m isobath (Figure 1b; Artana et al., 2018). At 38°S, the MC encounters the Brazil Current forming the Brazil-Malvinas Confluence. The surface eddy kinetic energy (EKE) at this region is among the greatest in the world ocean with values exceeding 2,000 cm 2 /s 2 (Figure 1c). In contrast, the EKE in the MC is rather small (200 cm 2 /s 2) since the Malvinas Plateau filters a large part of the mesoscale activity from Drake Passage (Artana et al., 2016). In situ observations have pointed at the possible existence of trapped waves (TW) propagating northward along the Patagonian slope. Velocity spectra obtained from current-meter moorings deployed at 41°S across the slope near the Brazil Malvinas Confluence showed large energy peaks between 5 and 110 days (Vivier & Provost, 1999; Vivier et al., 2001). Despite these observations, there is still no characterization of TW along the Patagonian slope. As the TW propagates rapidly, they are not entirely resolved in satellite-altimetry-derived maps of sea level anomalies (SLAs) (Ballarotta et al., 2019).

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“…Inverted echosounders and altimetry have been used to monitor the location of the Confluence and the baroclinic transport of the Brazil Current [e.g., Garzoli and Garraffo , 1989; Garzoli , 1993; Goni et al , 1996; Goni and Wainer , 2001]. Ocean models, whether analytical [e.g., Agra and Nof , 1993; Lebedev and Nof , 1997] or forced ocean general circulation models [e.g., Matano , 1993; Matano et al , 1993; Smith et al , 1994], showed the importance of the relative strength of the Brazil Current and MC transports in determining variations in the Confluence.…”

Section: Introductionmentioning

confidence: 99%

Variations in the Malvinas Current volume transport since October 1992

Spadone

Provost

2009

J. Geophys. Res.

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[1] We present a set of new current meter measurements collected to monitor the Malvinas Current (MC) near its merger with the Brazil Current at 40-41°S from December 2001 to February 2003 below a Jason-1 altimeter track. These measurements are compared to former measurements obtained 8 years earlier at the same location; they also provide new information on the core of the MC on the continental slope above the 1000-m isobath where a mooring had been previously lost. There, most of the velocity variation is along-isobath (80% of the variance) and shows a significant annual cycle. The two data sets provide coherent means and statistical parameters on the vertical structure of the flow. A 14-year-long time series of MC volume transport is derived using satellite altimetry. The good correlation between the altimetry-derived transport and the transport estimated from the current meter data persists in time (over 0.7 for each measurement period). A spectacular shift in the spectral composition of transport variations was observed: from 1992 until the end of 1997 transport variations occurred at rather short periods (50-90 days and to some degree around 180 days) whereas, after year 2000, longer periods including a seasonal cycle predominated. Altimetry-derived anomalies of surface geostrophic velocities along the core of the MC show a similar shift in spectral composition suggesting a remote-forcing origin.

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Collision of boundary currents: beyond a steady state

Cited by 10 publications

References 19 publications

Statistics of Brazil Current rings observed from AVHRR: 1993 to 1998

Statistics of Brazil Current rings observed from AVHRR: 1993 to 1998

Anatomy of Subinertial Waves Along the Patagonian Shelf Break in a 1/12° Global Operational Model

Variations in the Malvinas Current volume transport since October 1992

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