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The salinity signature of the cross-shelf exchanges in the Southwestern Atlantic Ocean: Numerical simulations.

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

Bottom Line: Dynamical analysis reveals that the cross-shelf flow has a dominant barotropic structure and, therefore, the SSS anomalies detected by Aquarius represent net mass exchanges between the shelf and the deep ocean.The net cross-shelf volume flux is 1.21 Sv.This outflow is largely compensated by an inflow from the Patagonian shelf.

View Article: PubMed Central - PubMed

Affiliation: College of Earth, Ocean and Atmospheric Sciences, Oregon State University Corvallis, Oregon, USA.

ABSTRACT

A high-resolution model is used to characterize the dominant patterns of sea surface salinity (SSS) variability generated by the freshwater discharges of the Rio de la Plata (RdlP) and the Patos/Mirim Lagoon in the southwestern Atlantic region. We identify three dominant modes of SSS variability. The first two, which have been discussed in previous studies, represent the seasonal and the interannual variations of the freshwater plumes over the continental shelf. The third mode of SSS variability, which has not been discussed hitherto, represents the salinity exchanges between the shelf and the deep ocean. A diagnostic study using floats and passive tracers identifies the pathways taken by the freshwater plumes. During the austral winter (JJA), the plumes leave the shelf region north of the BMC. During the austral summer (DJF), the plumes are entrained more directly into the BMC. A sensitivity study indicates that the high-frequency component of the wind stress forcing controls the vertical structure of the plumes while the low-frequency component of the wind stress forcing and the interannual variations of the RdlP discharge controls the horizontal structure of the plumes. Dynamical analysis reveals that the cross-shelf flow has a dominant barotropic structure and, therefore, the SSS anomalies detected by Aquarius represent net mass exchanges between the shelf and the deep ocean. The net cross-shelf volume flux is 1.21 Sv. This outflow is largely compensated by an inflow from the Patagonian shelf.

No MeSH data available.


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Vertical salinity profiles averaged in Region 1 (inset). EXP1: monthly winds; EXP2: climatological winds; EXP3: constant LPR discharge (24,000 m3/s).
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fig07: Vertical salinity profiles averaged in Region 1 (inset). EXP1: monthly winds; EXP2: climatological winds; EXP3: constant LPR discharge (24,000 m3/s).

Mentions: To assess the contributions of the wind stress forcing and the river discharge to the vertical mixing of the plume, we conducted an ancillary suite of sensitivity experiments. The benchmark case is the standard run described in the previous sections. The setup of the other experiments is identical to the benchmark case, except for the following changes: EXP1 is forced with monthly mean winds; EXP2 is forced with climatological monthly mean winds; and EXP3 is forced with daily winds but an average (and constant) RdlP discharge of 24,000 m3/s. The RdlP discharge in EXP1 and EXP2 is the same as in the benchmark case (monthly values). All the sensitivity experiments are run for the same period as the benchmark experiment (from 2001 to 2012). The changes in vertical mixing associated with the sensitivity experiments are evaluated through the comparison of vertical salinity profiles (Figure 7), which represent the horizontally averaged values of salinity in Region 1 during the year 2010 (Figure 1). We choose the year 2010 for our model intercomparison because it is preceded by the 2009 Niño, which generated an exceptional RdlP discharge of ∼53,000 m3/s.


The salinity signature of the cross-shelf exchanges in the Southwestern Atlantic Ocean: Numerical simulations.

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

Vertical salinity profiles averaged in Region 1 (inset). EXP1: monthly winds; EXP2: climatological winds; EXP3: constant LPR discharge (24,000 m3/s).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4508930&req=5

fig07: Vertical salinity profiles averaged in Region 1 (inset). EXP1: monthly winds; EXP2: climatological winds; EXP3: constant LPR discharge (24,000 m3/s).
Mentions: To assess the contributions of the wind stress forcing and the river discharge to the vertical mixing of the plume, we conducted an ancillary suite of sensitivity experiments. The benchmark case is the standard run described in the previous sections. The setup of the other experiments is identical to the benchmark case, except for the following changes: EXP1 is forced with monthly mean winds; EXP2 is forced with climatological monthly mean winds; and EXP3 is forced with daily winds but an average (and constant) RdlP discharge of 24,000 m3/s. The RdlP discharge in EXP1 and EXP2 is the same as in the benchmark case (monthly values). All the sensitivity experiments are run for the same period as the benchmark experiment (from 2001 to 2012). The changes in vertical mixing associated with the sensitivity experiments are evaluated through the comparison of vertical salinity profiles (Figure 7), which represent the horizontally averaged values of salinity in Region 1 during the year 2010 (Figure 1). We choose the year 2010 for our model intercomparison because it is preceded by the 2009 Niño, which generated an exceptional RdlP discharge of ∼53,000 m3/s.

Bottom Line: Dynamical analysis reveals that the cross-shelf flow has a dominant barotropic structure and, therefore, the SSS anomalies detected by Aquarius represent net mass exchanges between the shelf and the deep ocean.The net cross-shelf volume flux is 1.21 Sv.This outflow is largely compensated by an inflow from the Patagonian shelf.

View Article: PubMed Central - PubMed

Affiliation: College of Earth, Ocean and Atmospheric Sciences, Oregon State University Corvallis, Oregon, USA.

ABSTRACT

A high-resolution model is used to characterize the dominant patterns of sea surface salinity (SSS) variability generated by the freshwater discharges of the Rio de la Plata (RdlP) and the Patos/Mirim Lagoon in the southwestern Atlantic region. We identify three dominant modes of SSS variability. The first two, which have been discussed in previous studies, represent the seasonal and the interannual variations of the freshwater plumes over the continental shelf. The third mode of SSS variability, which has not been discussed hitherto, represents the salinity exchanges between the shelf and the deep ocean. A diagnostic study using floats and passive tracers identifies the pathways taken by the freshwater plumes. During the austral winter (JJA), the plumes leave the shelf region north of the BMC. During the austral summer (DJF), the plumes are entrained more directly into the BMC. A sensitivity study indicates that the high-frequency component of the wind stress forcing controls the vertical structure of the plumes while the low-frequency component of the wind stress forcing and the interannual variations of the RdlP discharge controls the horizontal structure of the plumes. Dynamical analysis reveals that the cross-shelf flow has a dominant barotropic structure and, therefore, the SSS anomalies detected by Aquarius represent net mass exchanges between the shelf and the deep ocean. The net cross-shelf volume flux is 1.21 Sv. This outflow is largely compensated by an inflow from the Patagonian shelf.

No MeSH data available.


Related in: MedlinePlus