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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.


(a) Mean sea surface salinity (SSS) map and (b) mean precipitation in the tropical Pacific averaged from September 2011 to August 2013. The three colored boxes in Figure 1a show the major areas of fresh water in the tropical Pacific that will be focused in this paper, including ITCZ (red), WPFP (blue), and EPFP (green). The black and magenta contours in Figure 1a indicate the 34.6 and 33 psu isohaline, respectively. The black contour in Figure 1b indicate the 100 mm/month isolines.
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fig01: (a) Mean sea surface salinity (SSS) map and (b) mean precipitation in the tropical Pacific averaged from September 2011 to August 2013. The three colored boxes in Figure 1a show the major areas of fresh water in the tropical Pacific that will be focused in this paper, including ITCZ (red), WPFP (blue), and EPFP (green). The black and magenta contours in Figure 1a indicate the 34.6 and 33 psu isohaline, respectively. The black contour in Figure 1b indicate the 100 mm/month isolines.

Mentions: In the tropical Pacific, the west to east zone of low sea surface salinity (SSS) features the western Pacific fresh pool (WPFP), intertropical convergence zone (ITCZ), and the eastern Pacific fresh pool (EPFP) responding to the high precipitation (Figure 1). The mixed layer salinity also shows the strongest interannual variations in these regions associated with the El Niño Southern Oscillation (ENSO) events [Hasson et al., 2013]. The importance of salinity in the tropical Pacific has been discussed in Delcroix and Hénin [1991]. For example, the SSS is a good indicator of the freshwater flux (evaporation minus precipitation) [Donguy and Hénin, 1976; Lagerloef et al., 2010]. In addition, the SSS variations are so large in the equatorial Pacific that it may dominate the mixed layer depth (MLD) and lead to the circumstance favorable for the formation of barrier layer (BL) [Lukas and Lindstrom, 1991]. This condition can be seen especially at the regions with large horizontal salinity gradients (i.e., the salinity fronts; SF), which are observed at the edge of strong atmospheric convection, such as the eastern edge of western Pacific warm pool (WPWP) [Picaut et al., 2001; Maes et al., 2006] or the western edge of EPFP [Alory et al., 2012].


Salinity fronts in the tropical Pacific Ocean.

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

(a) Mean sea surface salinity (SSS) map and (b) mean precipitation in the tropical Pacific averaged from September 2011 to August 2013. The three colored boxes in Figure 1a show the major areas of fresh water in the tropical Pacific that will be focused in this paper, including ITCZ (red), WPFP (blue), and EPFP (green). The black and magenta contours in Figure 1a indicate the 34.6 and 33 psu isohaline, respectively. The black contour in Figure 1b indicate the 100 mm/month isolines.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig01: (a) Mean sea surface salinity (SSS) map and (b) mean precipitation in the tropical Pacific averaged from September 2011 to August 2013. The three colored boxes in Figure 1a show the major areas of fresh water in the tropical Pacific that will be focused in this paper, including ITCZ (red), WPFP (blue), and EPFP (green). The black and magenta contours in Figure 1a indicate the 34.6 and 33 psu isohaline, respectively. The black contour in Figure 1b indicate the 100 mm/month isolines.
Mentions: In the tropical Pacific, the west to east zone of low sea surface salinity (SSS) features the western Pacific fresh pool (WPFP), intertropical convergence zone (ITCZ), and the eastern Pacific fresh pool (EPFP) responding to the high precipitation (Figure 1). The mixed layer salinity also shows the strongest interannual variations in these regions associated with the El Niño Southern Oscillation (ENSO) events [Hasson et al., 2013]. The importance of salinity in the tropical Pacific has been discussed in Delcroix and Hénin [1991]. For example, the SSS is a good indicator of the freshwater flux (evaporation minus precipitation) [Donguy and Hénin, 1976; Lagerloef et al., 2010]. In addition, the SSS variations are so large in the equatorial Pacific that it may dominate the mixed layer depth (MLD) and lead to the circumstance favorable for the formation of barrier layer (BL) [Lukas and Lindstrom, 1991]. This condition can be seen especially at the regions with large horizontal salinity gradients (i.e., the salinity fronts; SF), which are observed at the edge of strong atmospheric convection, such as the eastern edge of western Pacific warm pool (WPWP) [Picaut et al., 2001; Maes et al., 2006] or the western edge of EPFP [Alory et al., 2012].

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.