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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.


The T-S diagram of the values on each grid point along the cross line is shown in Figure 6b. The black contours indicate the density minus 1000 in kg/m3 and the color indicates the barrier layer thickness.
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fig07: The T-S diagram of the values on each grid point along the cross line is shown in Figure 6b. The black contours indicate the density minus 1000 in kg/m3 and the color indicates the barrier layer thickness.

Mentions: Both in situ Argo floats [Roemmich et al., 2009] and Aquarius satellite [Lagerloef et al., 2008] observations of SSS are used in this analysis. Aquarius satellite provides SSS data with an average spatial resolution of about 130 km [Lagerloef et al., 2008]. The 1° × 1° monthly salinity maps are generated at Earth and Space Research from Aquarius V2.5.1 (an interim test processing leading to the release of V3.0). Local polynomial fitting with 150 km radius is applied [Lilly and Lagerloef, 2008] and the intrabeam differences within the three beams of Aquarius are reduced by averaging the long-wave along track variations. Aquarius has been collected data since September 2011, so in this paper we use the time period from September 2011 to August 2013 to show 2 years of SSS data. For gridded in situ data analyses, we use the Asia-Pacific Data-Research Center (APDRC) of the International Pacific Research Center (IPRC) 1° × 1° Argo maps of SSS, SST, barrier layer thickness (BLT), and MLD generated with ∼500 km smoothing scale. For SST, we also use Optimum Interpolation (OI) SST V2 [Reynolds et al., 2007], which is obtained using both in situ and satellite SST. Here, we use the weekly data with 1° × 1° spatial resolution for generating the maps. The scope of this paper is to describe the major structures of these fronts, so 1° data averaged for each month data are used for maps. The monthly 1/3° × 1/3° SSS and SST are only used in the T-S diagram (Figure 7) to show the regional variations. For surface currents, we use the data from OSCAR (Ocean Surface Current Analyses–Real time; Dohan and Maximenko [2010]). OSCAR calculates the ocean surface velocity averaged in the upper 30 m from satellite fields, including near surface winds and sea surface height (SSH). The data are available from October 1992 until present. Monthly 1° × 1° data are used here and can be downloaded from the NASA PO.DACC (http://podaac.jpl.nasa.gov/). For precipitation, we use daily high-resolution precipitation of 1/4° × 1/4° from CMORPH (CPC MORPHing technique) [Joyce et al., 2004].


Salinity fronts in the tropical Pacific Ocean.

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

The T-S diagram of the values on each grid point along the cross line is shown in Figure 6b. The black contours indicate the density minus 1000 in kg/m3 and the color indicates the barrier layer thickness.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig07: The T-S diagram of the values on each grid point along the cross line is shown in Figure 6b. The black contours indicate the density minus 1000 in kg/m3 and the color indicates the barrier layer thickness.
Mentions: Both in situ Argo floats [Roemmich et al., 2009] and Aquarius satellite [Lagerloef et al., 2008] observations of SSS are used in this analysis. Aquarius satellite provides SSS data with an average spatial resolution of about 130 km [Lagerloef et al., 2008]. The 1° × 1° monthly salinity maps are generated at Earth and Space Research from Aquarius V2.5.1 (an interim test processing leading to the release of V3.0). Local polynomial fitting with 150 km radius is applied [Lilly and Lagerloef, 2008] and the intrabeam differences within the three beams of Aquarius are reduced by averaging the long-wave along track variations. Aquarius has been collected data since September 2011, so in this paper we use the time period from September 2011 to August 2013 to show 2 years of SSS data. For gridded in situ data analyses, we use the Asia-Pacific Data-Research Center (APDRC) of the International Pacific Research Center (IPRC) 1° × 1° Argo maps of SSS, SST, barrier layer thickness (BLT), and MLD generated with ∼500 km smoothing scale. For SST, we also use Optimum Interpolation (OI) SST V2 [Reynolds et al., 2007], which is obtained using both in situ and satellite SST. Here, we use the weekly data with 1° × 1° spatial resolution for generating the maps. The scope of this paper is to describe the major structures of these fronts, so 1° data averaged for each month data are used for maps. The monthly 1/3° × 1/3° SSS and SST are only used in the T-S diagram (Figure 7) to show the regional variations. For surface currents, we use the data from OSCAR (Ocean Surface Current Analyses–Real time; Dohan and Maximenko [2010]). OSCAR calculates the ocean surface velocity averaged in the upper 30 m from satellite fields, including near surface winds and sea surface height (SSH). The data are available from October 1992 until present. Monthly 1° × 1° data are used here and can be downloaded from the NASA PO.DACC (http://podaac.jpl.nasa.gov/). For precipitation, we use daily high-resolution precipitation of 1/4° × 1/4° from CMORPH (CPC MORPHing technique) [Joyce et al., 2004].

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.