Satellite Altimetry and Current‐Meter Velocities in the Malvinas Current at 41°S: Comparisons and Modes of Variations

Ferrari, Ramiro; Artana, Camila; Saraceno, Martín; Piola, Alberto R.; Provost, Christine

doi:10.1002/2017jc013340

Cited by 30 publications

(96 citation statements)

References 26 publications

(34 reference statements)

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“…Satellite altimeter‐derived geostrophic velocities are significantly correlated with 20 day low‐pass filtered current meter observations and corroborate the weak and strong regimes reported here (Ferrari et al, ). Ferrari et al () showed that the first two modes of variability explain up to 41% of the variance of sea‐level anomaly around the mooring location.…”

Section: Discussion and Summarysupporting

confidence: 88%

“…Mesoscale process is probably at the origin of the deepening of the water masses during the weak Malvinas period as suggested by Maamaatuaiahutapu et al () to explain the presence of SAMW at a depth of 800 m north of 38°S. In turn, eddy kinetic energy mesoscale process is stronger during the weak Malvinas period (Ferrari et al, ) and thus intrusions of subtropical waters associated with intense mesoscale variability may favor the deepening of the water masses.…”

Section: Discussion and Summarymentioning

confidence: 85%

“…This work presents the first time series of θ and S data collected in the northern Malvinas Current. Two complementary articles further discuss the results found here, particularly putting the results in a regional context based on the combined analysis of satellite altimetry data (Ferrari et al, ) and computing and analyzing the MC transport (Artana et al, ). The time series reported here revealed the changes in the structure of the water masses and how they relate with changes in the currents during 338 days.…”

Section: Discussion and Summarymentioning

confidence: 95%

“…Ferrari et al () showed that the first two modes of variability explain up to 41% of the variance of sea‐level anomaly around the mooring location. The first mode represents meridional migrations in the penetration of the MC, while the second mode represents zonal displacements of the Brazil Current overshoot (Ferrari et al, ). Both modes are associated with standing waves in the northern Argentine Basin, yet the forcing mechanism of such waves is still unclear (Ferrari et al, ).…”

Section: Discussion and Summarymentioning

confidence: 99%

“…The ADCP observations at A4 also offer an excellent opportunity to compare satellite‐derived geostrophic velocities with in situ currents. Ferrari et al () showed that geostrophic velocities computed from gridded data represent in situ velocity better than along‐track data. Here we show that gridded altimetry data represent adequately (rmsd ∼12 cm/s) in situ currents both for the strong and weak Malvinas periods between 200 and 500 m (supporting information Figure A2a).…”

Section: Discussion and Summarymentioning

confidence: 99%

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Malvinas Current at 40°S–41°S: First Assessment of Temperature and Salinity Temporal Variability

et al. 2018

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The temporal variability of 11 months of in situ velocity, temperature, and salinity data collected at five moorings deployed at 40°S–41°S across the shelf‐break in the Southwestern Atlantic is analyzed. Two distinct regimes characterized by strong and weak along‐slope velocities are present. During the strong regime the Malvinas Current flows northward through the moorings while during the nearly 5 months long weak regime reversals of the along‐slope velocities are frequently observed. Comparison with the previous in situ time series obtained in the same region shows that such an extended period of weak flow has not been previously observed. During the weak regime, Sub‐Antarctic Mode Water is observed over the 1,800 m isobath at an average depth of 500 m. Water masses occupying the upper 1,600 m during the strong regime deepen and shift eastward during the weak period. Satellite geostrophic velocities and sea surface temperature clearly show that the weak regime is due to a deflection to the east of the Malvinas Current, upstream of the mooring position. Analysis of the vertical structure of the currents indicate that during the weak regime the flow weakens mostly at the surface and presents a very small vertical shear. In contrast, during the strong regime currents are surface‐intensified. The change in the structure of the currents at the mooring location impacts the relationship between in situ and altimetry‐derived currents: during the weak regime altimetry adequately represents (rmsd 12 cm/s) in situ currents in the whole water column, while during strong regime rmsd are larger than 15 cm/s below 600 m depth.

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Section: Discussion and Summarysupporting

confidence: 88%

Section: Discussion and Summarymentioning

confidence: 85%

Section: Discussion and Summarymentioning

confidence: 95%

Section: Discussion and Summarymentioning

confidence: 99%

Section: Discussion and Summarymentioning

confidence: 99%

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Malvinas Current at 40°S–41°S: First Assessment of Temperature and Salinity Temporal Variability

et al. 2018

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Malvinas Current Volume Transport at 41°S: A 24 Yearlong Time Series Consistent With Mooring Data From 3 Decades and Satellite Altimetry

et al. 2018

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We combined altimetric data and the in situ data sets from three 10 years apart mooring deployments to compute a coherent and accurate volume transport time series of the Malvinas Current (MC) at 41°S. We used a method developed in Koenig et al. (2014) and explored three types of geostrophic shear to estimate the uncertainty derived from the lack of velocity data in the upper 300 m. The mean MC transport over 24 years in the upper 1,500 m is 37.1 ± 2.6 Sv and the standard deviation 6.6 ± 1 Sv. Since 1993, annual mean transports have varied from 32 to 41 Sv and the three in situ records corresponded to low annual mean transports. The MC transport time series is not stationary, its spectral content evolves with time showing significant energy at the 30–110 days, semiannual and annual period. The distribution of the MC volume transport anomalies is asymmetric, negatively skewed with larger negative anomalies than positive anomalies. Several transport maxima appear to result from cyclonic eddies that propagate northwestward following the 4,000–5,000 m isobaths and locally reinforce the circulation on the slope when they reach 41°S. During transport maxima, the northernmost extension of the Subantarctic Front (SAF) remains at its mean location (39.5°S). During minima, the SAF migrates southward of 41°S as positive anomalies shed by the Brazil Current overshoot moves westward onto the slope. Apart from continental trapped waves, changes in the MC volume transport at 41°S show no correlation with upstream conditions on the continental slope.

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Evaluation of the sub-annual sea level anomalies in the continental shelf of the Southwestern Atlantic and their relation to wind variability

Juhl,

Passaro,

Dettmering

et al. 2024

Ocean Dynamics

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We have analyzed the relationship between wind variability and sea level anomalies (SLA) on the Southwestern Atlantic Continental Shelf, focusing on sub-annual temporal scales. For this, we tested the capability of gridded altimetry to represent wind-driven SLA and compared results using an oceanographic model and tide gauge data. The present study used coherence analysis to analyze frequencies for which SLA and wind stress are coherent. The altimetry-SLA were found to have less energy below the three-month period compared to the model SLA. The coherence of along-shore wind stress and altimetry SLA was only significant for > 50 days (d), while the model SLA showed significant agreement in all periods considered, 20 d to annual. We further showed that geostrophic velocities on the continental shelf agreed significantly with SLA for > 50 d. As a result of an Empirical Orthogonal Function (EOF) analysis, we found that the second mode is highly coherent with the along-shore wind stress and accounts for 18.1% and 10.7% of variability in the model and altimetry sea level anomalies, respectively.

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Satellite Altimetry and Current‐Meter Velocities in the Malvinas Current at 41°S: Comparisons and Modes of Variations

Cited by 30 publications

References 26 publications

Malvinas Current at 40°S–41°S: First Assessment of Temperature and Salinity Temporal Variability

Malvinas Current at 40°S–41°S: First Assessment of Temperature and Salinity Temporal Variability

Malvinas Current Volume Transport at 41°S: A 24 Yearlong Time Series Consistent With Mooring Data From 3 Decades and Satellite Altimetry

Evaluation of the sub-annual sea level anomalies in the continental shelf of the Southwestern Atlantic and their relation to wind variability

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