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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.


Hovmöller diagrams of (a) SSS in psu, (b) SST in °C, (c) precipitation in mm/day, (d) SSS gradient in psu/km (e) meridional currents in m/s, and (f) barrier layer thickness in meters over the eastern Pacific fresh pool, averaged between 90° and 110°W. The black contours in Figures 9b, 9e, and 9f are the 27.5°C isotherm, 0 m/s, and 0 m isolines, respectively.
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fig09: Hovmöller diagrams of (a) SSS in psu, (b) SST in °C, (c) precipitation in mm/day, (d) SSS gradient in psu/km (e) meridional currents in m/s, and (f) barrier layer thickness in meters over the eastern Pacific fresh pool, averaged between 90° and 110°W. The black contours in Figures 9b, 9e, and 9f are the 27.5°C isotherm, 0 m/s, and 0 m isolines, respectively.

Mentions: To demonstrate the meridional variations of the SSS in the eastern Pacific on a seasonal cycle, Figure 9 shows the Hovmöller diagrams averaged from 90° to 110°W. The lowest SSS (<33 psu) is observed under the ITCZ in the northern hemisphere, especially around October (Figure 9a). A branch of less fresh water extends from the equator to around 5°S from February to May. The warm water split by the cool upwelling at the equator forms the essential SST pattern that contributes to the double ITCZ (Figure 9b) [Zhang, 2001]. The black contours in Figure 9b represent the 27.5°C isotherm being separating at the equator. The strong precipitation corresponds to the warm pool variations, with the strongest intensity over the ITCZ in the northern hemisphere and a weaker regional precipitation pattern seen ∼5°S during the boreal spring. The regional freshening forms sharp SF (Figure 9d) at the south boundary of the southern ITCZ. The SF in the eastern Pacific visibly shows a southward extension from 5°S in February to 10°S in May, which is not seen in the precipitation data (Figure 9c). The results imply that the southward extension of the SF may be associated with the meridional currents (Figure 9e) carrying the freshwater southward. The results imply that the salinity pattern in the EPFP may be influenced by both the precipitation and the meridional advections.


Salinity fronts in the tropical Pacific Ocean.

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

Hovmöller diagrams of (a) SSS in psu, (b) SST in °C, (c) precipitation in mm/day, (d) SSS gradient in psu/km (e) meridional currents in m/s, and (f) barrier layer thickness in meters over the eastern Pacific fresh pool, averaged between 90° and 110°W. The black contours in Figures 9b, 9e, and 9f are the 27.5°C isotherm, 0 m/s, and 0 m isolines, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig09: Hovmöller diagrams of (a) SSS in psu, (b) SST in °C, (c) precipitation in mm/day, (d) SSS gradient in psu/km (e) meridional currents in m/s, and (f) barrier layer thickness in meters over the eastern Pacific fresh pool, averaged between 90° and 110°W. The black contours in Figures 9b, 9e, and 9f are the 27.5°C isotherm, 0 m/s, and 0 m isolines, respectively.
Mentions: To demonstrate the meridional variations of the SSS in the eastern Pacific on a seasonal cycle, Figure 9 shows the Hovmöller diagrams averaged from 90° to 110°W. The lowest SSS (<33 psu) is observed under the ITCZ in the northern hemisphere, especially around October (Figure 9a). A branch of less fresh water extends from the equator to around 5°S from February to May. The warm water split by the cool upwelling at the equator forms the essential SST pattern that contributes to the double ITCZ (Figure 9b) [Zhang, 2001]. The black contours in Figure 9b represent the 27.5°C isotherm being separating at the equator. The strong precipitation corresponds to the warm pool variations, with the strongest intensity over the ITCZ in the northern hemisphere and a weaker regional precipitation pattern seen ∼5°S during the boreal spring. The regional freshening forms sharp SF (Figure 9d) at the south boundary of the southern ITCZ. The SF in the eastern Pacific visibly shows a southward extension from 5°S in February to 10°S in May, which is not seen in the precipitation data (Figure 9c). The results imply that the southward extension of the SF may be associated with the meridional currents (Figure 9e) carrying the freshwater southward. The results imply that the salinity pattern in the EPFP may be influenced by both the precipitation and the meridional advections.

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.