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Water Vapor Transfer and Near-Surface Salinity Contrasts in the North Atlantic Ocean - PubMed

  • ️Mon Jan 01 2018

Water Vapor Transfer and Near-Surface Salinity Contrasts in the North Atlantic Ocean

James Reagan et al. Sci Rep. 2018.

Abstract

Maintaining North Atlantic (NA) intra-basin near-surface salinity (NSS) contrast between the high NSS (>37.0) in the subtropical NA (STNA) and low NSS (<35.0) in the subpolar NA (SPNA) has been shown to be important in sustaining the strength of the Atlantic Meridional Overturning Circulation. Evaporation (E) exceeding precipitation (P) in the STNA is primarily responsible for the high NSS there, whereas P dominating E in the SPNA contributes to its low NSS. With a basic understanding of NA intra-basin moisture transport, a correlation analysis was conducted between E-P/NSS over the NA subpolar gyre (SPG) and E-P across the rest of the NA over the 1985-2012 time period. Significant anti-correlations exist between E-P/NSS over the NA SPG and E-P over the central/northern STNA. This suggests that during times of high E over the central/northern STNA there is high (low) precipitation (NSS) over the SPG demonstrating a relationship likely exists between E over the STNA and NSS over the SPG. The maximum anti-correlated area is poleward of the maximum E-P location in the STNA, which is examined. These results provide a first step to ultimately utilizing NSS in the NA as a proxy for estimating changes in the hydrological cycle.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1

Schematic of the North Atlantic moisture transport. The background image with colored shadings of salinity is from the Aquarius satellite and courteous of NASA’s Goddard Space Flight Center Scientific Visualization Studio (

https://svs.gsfc.nasa.gov/4046

). Evaporation minus precipitation (E-P) is indicated by the white shadings, and atmospheric moisture transport is shown by the various arrows.

Figure 2
Figure 2

The 1985–2012 North Atlantic (a) Climatological E – P (mm*day−1), (b) correlation between the areal averaged subpolar gyre E-P (red-contoured rectangle in b) and the E-P over the rest of the North Atlantic Ocean, and c) time series of E-P over the subpolar NA (red box in b) and E-P over the subtropical NA (green box in b). Correlations and time series are based on the 1985–1994, 1995–2004, and 2005–2012 monthly climatological E and P fields (N = 36). The red box in (a) designates the subpolar North Atlantic (SPNA) region and the green box designates the subtropical North Atlantic (STNA). Black dotted line in (b) represents the region where correlation is lower than −0.330 (95% CI). This figure was created using the Grid Analysis and Display System (GrADS) software (available at:

http://cola.gmu.edu/grads/

).

Figure 3
Figure 3

Similar to Fig. 2, but (a) represents correlation between area-average subpolar NSS (red box) and NA E-P and (b) is the normalized time series of NSS from the red box in (a) and E-P from the green box in (a). Black dotted line in (a) represents the region where correlation is lower than −0.330 (95% CI). This figure was created using the GrADS software.

Figure 4
Figure 4

The 1985–2012 seasonal average of the vertically integrated moisture flux divergence (VIMFD, mm*day−1, shaded) and the divergent component of the moisture fluxes (DCMF, kg*m−1*sec−1, vectors) for (a) winter (JFM), (b) spring (AMJ), (c) summer (JAS), and (d) fall (OND). Orange shades represent moisture divergence and blue shades represent moisture convergence. This figure was created using the GrADS software.

Figure 5
Figure 5

The 1985–2012 zonal average of the meridional component of the DCMF (kg*m−1*sec−1, black line) and of the VIMFD (10*mm*day−1, red line) for (a) winter (JFM), (b) spring (AMJ), (c) summer (JAS), and (d) fall (OND). The zonal average was taken over the 60°W–20°W area (see Fig. 4a–d). This figure was created using the GrADS software.

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