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Salinity fronts in the tropical Pacific Ocean.

Kao HY, Lagerloef GS - J Geophys Res Oceans (2015)

Bottom Line: In the eastern Pacific, we observe a southward extension of the SF in the boreal spring that could be driven by both precipitation and horizontal advection.In the western Pacific, the importance of these newly resolved SF associated with the western Pacific warm/fresh pool and El Niño southern oscillations are also discussed in the context of prior literature.The main conclusions of this study are that (a) Aquarius satellite salinity measurements reveal the heretofore unknown proliferation, structure, and variability of surface salinity fronts, and that (b) the fine-scale structures of the SF in the tropical Pacific yield important new information on the regional air-sea interaction and the upper ocean dynamics.

View Article: PubMed Central - PubMed

Affiliation: Earth and Space Research Seattle, Washington, USA.

ABSTRACT

This study delineates the salinity fronts (SF) across the tropical Pacific, and describes their variability and regional dynamical significance using Aquarius satellite observations. From the monthly maps of the SF, we find that the SF in the tropical Pacific are (1) usually observed around the boundaries of the fresh pool under the intertropical convergence zone (ITCZ), (2) stronger in boreal autumn than in other seasons, and (3) usually stronger in the eastern Pacific than in the western Pacific. The relationship between the SF and the precipitation and the surface velocity are also discussed. We further present detailed analysis of the SF in three key tropical Pacific regions. Extending zonally around the ITCZ, where the temperature is nearly homogeneous, we find the strong SF of 1.2 psu from 7° to 11°N to be the main contributor of the horizontal density difference of 0.8 kg/m(3). In the eastern Pacific, we observe a southward extension of the SF in the boreal spring that could be driven by both precipitation and horizontal advection. In the western Pacific, the importance of these newly resolved SF associated with the western Pacific warm/fresh pool and El Niño southern oscillations are also discussed in the context of prior literature. The main conclusions of this study are that (a) Aquarius satellite salinity measurements reveal the heretofore unknown proliferation, structure, and variability of surface salinity fronts, and that (b) the fine-scale structures of the SF in the tropical Pacific yield important new information on the regional air-sea interaction and the upper ocean dynamics.

No MeSH data available.


Maps of (a) SST, (b) salinity front and (c) barrier layer thickness (BLT) in October 2012. The green/black lines in Figures 6b/6a and 6c show the cross section of the strong SF used in Figure 7.
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fig06: Maps of (a) SST, (b) salinity front and (c) barrier layer thickness (BLT) in October 2012. The green/black lines in Figures 6b/6a and 6c show the cross section of the strong SF used in Figure 7.

Mentions: As seen in Figures 2 and 3, the SF are well defined at the boundaries of the ITCZ rain band with the strongest gradients occurring September–October–November. In this season, there is also thick BL observed over the whole Pacific ITCZ (Figure 6c), especially where the SF is the strongest (Figure 6b). The results show that the SF can be an indicator of the existence of BL not only in the western Pacific [Maes et al., 2005] but also under the ITCZ. The thick green line (7°–11°N, 120°W) in Figure 6b indicates a transect crossing through a strong SF. Along this line, the SST is nearly homogeneous (black line in Figure 6a) and the BLT is around 18 m (black line in Figure 6c). The relationships between SST, SSS, SSD, and BLT across this SF are displayed in a modified T-S diagram (Figure 7). The BLT (color) is plotted at every grid point with 1/3° resolution along the transect. SST is quite constant at around 27.8∼28.1°C, whereas, the SSS varies from 33.1 to 34.3 psu, indicating the existence strong SF with strength of 1.2 psu from 7°N to 11°N (∼444.78 km), and the salinity-based density variations as much as 0.8 kg/m3 along this cross line. These results show an example of strong SF detected with Aquarius in the area where the SST has little variations and a sharp density front can be formed majorly contributed by the SSS. The results also show that strong density variance (density fronts) can be calculated combining the Aquarius SSS and SST from satellite observations. The in situ data alone are too sparse to resolve the SF.


Salinity fronts in the tropical Pacific Ocean.

Kao HY, Lagerloef GS - J Geophys Res Oceans (2015)

Maps of (a) SST, (b) salinity front and (c) barrier layer thickness (BLT) in October 2012. The green/black lines in Figures 6b/6a and 6c show the cross section of the strong SF used in Figure 7.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4508928&req=5

fig06: Maps of (a) SST, (b) salinity front and (c) barrier layer thickness (BLT) in October 2012. The green/black lines in Figures 6b/6a and 6c show the cross section of the strong SF used in Figure 7.
Mentions: As seen in Figures 2 and 3, the SF are well defined at the boundaries of the ITCZ rain band with the strongest gradients occurring September–October–November. In this season, there is also thick BL observed over the whole Pacific ITCZ (Figure 6c), especially where the SF is the strongest (Figure 6b). The results show that the SF can be an indicator of the existence of BL not only in the western Pacific [Maes et al., 2005] but also under the ITCZ. The thick green line (7°–11°N, 120°W) in Figure 6b indicates a transect crossing through a strong SF. Along this line, the SST is nearly homogeneous (black line in Figure 6a) and the BLT is around 18 m (black line in Figure 6c). The relationships between SST, SSS, SSD, and BLT across this SF are displayed in a modified T-S diagram (Figure 7). The BLT (color) is plotted at every grid point with 1/3° resolution along the transect. SST is quite constant at around 27.8∼28.1°C, whereas, the SSS varies from 33.1 to 34.3 psu, indicating the existence strong SF with strength of 1.2 psu from 7°N to 11°N (∼444.78 km), and the salinity-based density variations as much as 0.8 kg/m3 along this cross line. These results show an example of strong SF detected with Aquarius in the area where the SST has little variations and a sharp density front can be formed majorly contributed by the SSS. The results also show that strong density variance (density fronts) can be calculated combining the Aquarius SSS and SST from satellite observations. The in situ data alone are too sparse to resolve the SF.

Bottom Line: In the eastern Pacific, we observe a southward extension of the SF in the boreal spring that could be driven by both precipitation and horizontal advection.In the western Pacific, the importance of these newly resolved SF associated with the western Pacific warm/fresh pool and El Niño southern oscillations are also discussed in the context of prior literature.The main conclusions of this study are that (a) Aquarius satellite salinity measurements reveal the heretofore unknown proliferation, structure, and variability of surface salinity fronts, and that (b) the fine-scale structures of the SF in the tropical Pacific yield important new information on the regional air-sea interaction and the upper ocean dynamics.

View Article: PubMed Central - PubMed

Affiliation: Earth and Space Research Seattle, Washington, USA.

ABSTRACT

This study delineates the salinity fronts (SF) across the tropical Pacific, and describes their variability and regional dynamical significance using Aquarius satellite observations. From the monthly maps of the SF, we find that the SF in the tropical Pacific are (1) usually observed around the boundaries of the fresh pool under the intertropical convergence zone (ITCZ), (2) stronger in boreal autumn than in other seasons, and (3) usually stronger in the eastern Pacific than in the western Pacific. The relationship between the SF and the precipitation and the surface velocity are also discussed. We further present detailed analysis of the SF in three key tropical Pacific regions. Extending zonally around the ITCZ, where the temperature is nearly homogeneous, we find the strong SF of 1.2 psu from 7° to 11°N to be the main contributor of the horizontal density difference of 0.8 kg/m(3). In the eastern Pacific, we observe a southward extension of the SF in the boreal spring that could be driven by both precipitation and horizontal advection. In the western Pacific, the importance of these newly resolved SF associated with the western Pacific warm/fresh pool and El Niño southern oscillations are also discussed in the context of prior literature. The main conclusions of this study are that (a) Aquarius satellite salinity measurements reveal the heretofore unknown proliferation, structure, and variability of surface salinity fronts, and that (b) the fine-scale structures of the SF in the tropical Pacific yield important new information on the regional air-sea interaction and the upper ocean dynamics.

No MeSH data available.