Limits...
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.


Related in: MedlinePlus

(a) Time series of the sea surface salinities (SSS) averaged over Region 1 (red line), the alongshelf component of the wind stress forcing averaged over Region 1 (gray line) and the Rio de la Plata (RdlP) discharge (blue line); (b) wavelet spectra of the time series of the SSS averaged over Region 1; (c) idem for the alongshelf wind stress forcing. The black contours show regions with a confidence level higher than 95%. Hatched regions indicate the cone of influence. The time series for the wavelet analyses have been normalized thus the color bar does not have units.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4508930&req=5

fig02: (a) Time series of the sea surface salinities (SSS) averaged over Region 1 (red line), the alongshelf component of the wind stress forcing averaged over Region 1 (gray line) and the Rio de la Plata (RdlP) discharge (blue line); (b) wavelet spectra of the time series of the SSS averaged over Region 1; (c) idem for the alongshelf wind stress forcing. The black contours show regions with a confidence level higher than 95%. Hatched regions indicate the cone of influence. The time series for the wavelet analyses have been normalized thus the color bar does not have units.

Mentions: To assess the variability of the shelf region, we first compare the time series of the SSS and the wind stress forcing averaged over Region 1 (Figure 1) and the time series of RdlP discharge (Figure 2). The time series of the alongshelf winds is modulated by strong seasonal oscillations between southwesterly winds (i.e., from the southwest) during the winter and northeasterly winds (i.e., from the northeast) during the summer. There is a strong correspondence between the alongshelf winds and the SSS anomalies [Piola et al., 2005; Soares et al., 2007b; Palma et al., 2008]. During the winter, southwesterly winds create geostrophic currents that advect the relatively freshwaters of the RdlP toward the north, thus generating negative SSS anomalies over the downstream region. These patterns reverse during the summer when northeasterly winds reverse the direction of the currents, which advect salty waters from the Brazilian shelf to the south, thus generating positive (saltier) SSS anomalies. The average time lag between the peaks of the winds and the peaks of the SSS anomalies is approximately 45 days, which can be interpreted as the time that it takes to change the average SSS of Region 1.


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)

(a) Time series of the sea surface salinities (SSS) averaged over Region 1 (red line), the alongshelf component of the wind stress forcing averaged over Region 1 (gray line) and the Rio de la Plata (RdlP) discharge (blue line); (b) wavelet spectra of the time series of the SSS averaged over Region 1; (c) idem for the alongshelf wind stress forcing. The black contours show regions with a confidence level higher than 95%. Hatched regions indicate the cone of influence. The time series for the wavelet analyses have been normalized thus the color bar does not have units.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig02: (a) Time series of the sea surface salinities (SSS) averaged over Region 1 (red line), the alongshelf component of the wind stress forcing averaged over Region 1 (gray line) and the Rio de la Plata (RdlP) discharge (blue line); (b) wavelet spectra of the time series of the SSS averaged over Region 1; (c) idem for the alongshelf wind stress forcing. The black contours show regions with a confidence level higher than 95%. Hatched regions indicate the cone of influence. The time series for the wavelet analyses have been normalized thus the color bar does not have units.
Mentions: To assess the variability of the shelf region, we first compare the time series of the SSS and the wind stress forcing averaged over Region 1 (Figure 1) and the time series of RdlP discharge (Figure 2). The time series of the alongshelf winds is modulated by strong seasonal oscillations between southwesterly winds (i.e., from the southwest) during the winter and northeasterly winds (i.e., from the northeast) during the summer. There is a strong correspondence between the alongshelf winds and the SSS anomalies [Piola et al., 2005; Soares et al., 2007b; Palma et al., 2008]. During the winter, southwesterly winds create geostrophic currents that advect the relatively freshwaters of the RdlP toward the north, thus generating negative SSS anomalies over the downstream region. These patterns reverse during the summer when northeasterly winds reverse the direction of the currents, which advect salty waters from the Brazilian shelf to the south, thus generating positive (saltier) SSS anomalies. The average time lag between the peaks of the winds and the peaks of the SSS anomalies is approximately 45 days, which can be interpreted as the time that it takes to change the average SSS of Region 1.

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