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The salinity signature of the cross-shelf exchanges in the Southwestern Atlantic Ocean: Satellite observations.

Guerrero RA, Piola AR, Fenco H, Matano RP, Combes V, Chao Y, James C, Palma ED, Saraceno M, Strub PT - J Geophys Res Oceans (2014)

Bottom Line: However, the combined analysis of SSS, satellite-derived sea surface elevation and surface velocity data suggest that the precise location of the export of shelf waters depends on offshore circulation patterns, such as the location of the Brazil Malvinas Confluence and mesoscale eddies and meanders of the Brazil Current.The satellite data indicate that in summer, mixtures of low-salinity shelf waters are swiftly driven toward the ocean interior along the axis of the Brazil/Malvinas Confluence.Satellite salinity sensors capture low-salinity detrainment events from shelves SW Atlantic low-salinity detrainments cause highest basin-scale variability In summer low-salinity detrainments cause extended low-salinity anomalies.

View Article: PubMed Central - PubMed

Affiliation: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP) Mar del Plata, Argentina.

ABSTRACT

: Satellite-derived sea surface salinity (SSS) data from Aquarius and SMOS are used to study the shelf-open ocean exchanges in the western South Atlantic near 35°S. Away from the tropics, these exchanges cause the largest SSS variability throughout the South Atlantic. The data reveal a well-defined seasonal pattern of SSS during the analyzed period and of the location of the export of low-salinity shelf waters. In spring and summer, low-salinity waters over the shelf expand offshore and are transferred to the open ocean primarily southeast of the river mouth (from 36°S to 37°30'S). In contrast, in fall and winter, low-salinity waters extend along a coastal plume and the export path to the open ocean distributes along the offshore edge of the plume. The strong seasonal SSS pattern is modulated by the seasonality of the along-shelf component of the wind stress over the shelf. However, the combined analysis of SSS, satellite-derived sea surface elevation and surface velocity data suggest that the precise location of the export of shelf waters depends on offshore circulation patterns, such as the location of the Brazil Malvinas Confluence and mesoscale eddies and meanders of the Brazil Current. The satellite data indicate that in summer, mixtures of low-salinity shelf waters are swiftly driven toward the ocean interior along the axis of the Brazil/Malvinas Confluence. In winter, episodic wind reversals force the low-salinity coastal plume offshore where they mix with tropical waters within the Brazil Current and create a warmer variety of low-salinity waters in the open ocean.

Key points: Satellite salinity sensors capture low-salinity detrainment events from shelves SW Atlantic low-salinity detrainments cause highest basin-scale variability In summer low-salinity detrainments cause extended low-salinity anomalies.

No MeSH data available.


Related in: MedlinePlus

Evolution of SSS-Aq from 27 November 2011 to 1 January 2012 overlapped on OSCAR current vectors, scale shown in lower right-hand side on each panel. The gray thick line indicates the 200 m isobath.
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fig08: Evolution of SSS-Aq from 27 November 2011 to 1 January 2012 overlapped on OSCAR current vectors, scale shown in lower right-hand side on each panel. The gray thick line indicates the 200 m isobath.

Mentions: The low-salinity detrainment event observed in December 2011 is clearly displayed on the Aquarius and SMOS SSS distributions (Figures 5a and 5b). This event was preceded by a period of relatively high outflow (Figure 7e) and northeasterly winds (Figure 7c). The detailed evolution of this low-salinity detrainment event is presented in Figure 8. On 27 November, the 33.5 isohaline is located 150 km offshore from the 200 m isobath and extends more than 300 km along the shelf break (Figure 8a). The OSCAR surface current field reveals a strong southward flow (∼1 m s−1) over the eastern edge of the low-salinity cell at 37°S. On 4 December the low-salinity waters develops into a plume extending 220 km southeastward from the shelf break near 39°S (Figure 8b), while the surface currents present a strong southeastward flow. At this time the low-salinity waters appear to be advected southward and offshore along the western and southern edges of anticyclonic eddy A1 (Figures 8b and 8c). On 11 December the low-salinity tongue extends further offshore (350 km) and a salty eddy (SSS > 35.5) develops northeast of the plume with the low-salinity water being advected around the eddy rim (Figure 8c). The eddy to low-salinity filament transition is associated with a salinity contrast ∼2. The eddy persists in the following weeks while by 1 January the low-salinity signal weakens significantly (SSS > 34.0) as it mixes with the salty background waters (Figures 8d–8f). By 18 December an additional anticyclonic eddy develops centered near 44°S–53°W, whose core is also characterized by high salinity (Figures 8d–8f). The extreme low in SSS-Aq and their off shelf advection from November 2011 to February 2012 (Figures 6b and 6c), are consistent with relatively strong and persistent northeasterly winds over the shelf (Figure 7c) and the development of an intense anticyclonic ring offshore (A1 in Figure 8). Though the SMOS time series do not reproduce the December 2011 event as strongly as Aquarius, a similar low-salinity detrainment also associated with strong northeasterly wind events is observed in the SMOS data in January 2011 (Figures 7b and 7c). This event, however, was preceded by five months of lower than averaged river discharge (Figure 7e).


The salinity signature of the cross-shelf exchanges in the Southwestern Atlantic Ocean: Satellite observations.

Guerrero RA, Piola AR, Fenco H, Matano RP, Combes V, Chao Y, James C, Palma ED, Saraceno M, Strub PT - J Geophys Res Oceans (2014)

Evolution of SSS-Aq from 27 November 2011 to 1 January 2012 overlapped on OSCAR current vectors, scale shown in lower right-hand side on each panel. The gray thick line indicates the 200 m isobath.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4508963&req=5

fig08: Evolution of SSS-Aq from 27 November 2011 to 1 January 2012 overlapped on OSCAR current vectors, scale shown in lower right-hand side on each panel. The gray thick line indicates the 200 m isobath.
Mentions: The low-salinity detrainment event observed in December 2011 is clearly displayed on the Aquarius and SMOS SSS distributions (Figures 5a and 5b). This event was preceded by a period of relatively high outflow (Figure 7e) and northeasterly winds (Figure 7c). The detailed evolution of this low-salinity detrainment event is presented in Figure 8. On 27 November, the 33.5 isohaline is located 150 km offshore from the 200 m isobath and extends more than 300 km along the shelf break (Figure 8a). The OSCAR surface current field reveals a strong southward flow (∼1 m s−1) over the eastern edge of the low-salinity cell at 37°S. On 4 December the low-salinity waters develops into a plume extending 220 km southeastward from the shelf break near 39°S (Figure 8b), while the surface currents present a strong southeastward flow. At this time the low-salinity waters appear to be advected southward and offshore along the western and southern edges of anticyclonic eddy A1 (Figures 8b and 8c). On 11 December the low-salinity tongue extends further offshore (350 km) and a salty eddy (SSS > 35.5) develops northeast of the plume with the low-salinity water being advected around the eddy rim (Figure 8c). The eddy to low-salinity filament transition is associated with a salinity contrast ∼2. The eddy persists in the following weeks while by 1 January the low-salinity signal weakens significantly (SSS > 34.0) as it mixes with the salty background waters (Figures 8d–8f). By 18 December an additional anticyclonic eddy develops centered near 44°S–53°W, whose core is also characterized by high salinity (Figures 8d–8f). The extreme low in SSS-Aq and their off shelf advection from November 2011 to February 2012 (Figures 6b and 6c), are consistent with relatively strong and persistent northeasterly winds over the shelf (Figure 7c) and the development of an intense anticyclonic ring offshore (A1 in Figure 8). Though the SMOS time series do not reproduce the December 2011 event as strongly as Aquarius, a similar low-salinity detrainment also associated with strong northeasterly wind events is observed in the SMOS data in January 2011 (Figures 7b and 7c). This event, however, was preceded by five months of lower than averaged river discharge (Figure 7e).

Bottom Line: However, the combined analysis of SSS, satellite-derived sea surface elevation and surface velocity data suggest that the precise location of the export of shelf waters depends on offshore circulation patterns, such as the location of the Brazil Malvinas Confluence and mesoscale eddies and meanders of the Brazil Current.The satellite data indicate that in summer, mixtures of low-salinity shelf waters are swiftly driven toward the ocean interior along the axis of the Brazil/Malvinas Confluence.Satellite salinity sensors capture low-salinity detrainment events from shelves SW Atlantic low-salinity detrainments cause highest basin-scale variability In summer low-salinity detrainments cause extended low-salinity anomalies.

View Article: PubMed Central - PubMed

Affiliation: Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP) Mar del Plata, Argentina.

ABSTRACT

: Satellite-derived sea surface salinity (SSS) data from Aquarius and SMOS are used to study the shelf-open ocean exchanges in the western South Atlantic near 35°S. Away from the tropics, these exchanges cause the largest SSS variability throughout the South Atlantic. The data reveal a well-defined seasonal pattern of SSS during the analyzed period and of the location of the export of low-salinity shelf waters. In spring and summer, low-salinity waters over the shelf expand offshore and are transferred to the open ocean primarily southeast of the river mouth (from 36°S to 37°30'S). In contrast, in fall and winter, low-salinity waters extend along a coastal plume and the export path to the open ocean distributes along the offshore edge of the plume. The strong seasonal SSS pattern is modulated by the seasonality of the along-shelf component of the wind stress over the shelf. However, the combined analysis of SSS, satellite-derived sea surface elevation and surface velocity data suggest that the precise location of the export of shelf waters depends on offshore circulation patterns, such as the location of the Brazil Malvinas Confluence and mesoscale eddies and meanders of the Brazil Current. The satellite data indicate that in summer, mixtures of low-salinity shelf waters are swiftly driven toward the ocean interior along the axis of the Brazil/Malvinas Confluence. In winter, episodic wind reversals force the low-salinity coastal plume offshore where they mix with tropical waters within the Brazil Current and create a warmer variety of low-salinity waters in the open ocean.

Key points: Satellite salinity sensors capture low-salinity detrainment events from shelves SW Atlantic low-salinity detrainments cause highest basin-scale variability In summer low-salinity detrainments cause extended low-salinity anomalies.

No MeSH data available.


Related in: MedlinePlus