What is the average salinity of the pacific ocean

Land masses have a higher emissivity than the ocean, so any measurement close to land tends to be skewed by its brightness. Over time, the Aquarius research team should be able to calibrate the measurements and develop mathematical tools to better distinguish the salt signal. But for now, the measurements are so new that the team is still working on the big picture of ocean salinity.

Aquarius is the first NASA instrument specifically designed to study surface ocean salinity from space, and it does so at a rate of , measurements per month. It uses three passive microwave sensors, called radiometers, to record the thermal signal from the oceans' top 10 millimeters about 0. Most global precipitation and evaporation events take place over the ocean and are very difficult to measure.

Animation by Robert Simmon. One year after its launch, the Aquarius instrument is giving ocean sciences its first global view of sea surface salinity. Image of the Day Water. Examining temperatures from the depths of the ocean, JPL scientists have found that lower layers of the Western Pacific and Indian Oceans grew much warmer during a decade when surface temperatures cooled.

Image of the Day Heat Water. Both experiments reveal that the velocity field in the SPG is responsible for the halocline formation on the western side of the wide sinking region. Neither of these patterns in isolation lead to the observed differences in SPG salinities.

In the following, we show that, in isolation, neither the gyral velocities alone nor the MOC velocity alone can lead to a halocline in the wide-basin SPG. We first show the salinity distribution with advection by idealized vertically integrated velocities U gyre and V gyre representing the gyres in the 2D model. The resulting horizontally nondivergent transport is described by a single streamfunction shown in Fig.

Figure 13 shows the distribution of the resulting tracer solution of 8 , forced by the zonally uniform freshwater flux of Fig.

In the along-streamlines direction, the dominant balance is between the isopycnal advection terms and the surface salinity flux. In the across-streamlines direction, the dominant balance is between the isopycnal diffusion terms and the surface salinity flux. These differences are too small to explain the preference for narrow sinking seen in the 3D model, and a scale analysis in appendix B confirms that the salinity in this configuration is independent of basin width.

We now examine the salinity distribution with a velocity field characterized by sinking and a western boundary current associated with the MOC without wind-driven gyres.

The velocities U , V and in 8 are defined analytically. They are confined to a western boundary current in a single basin fed by upwelling in the periodic channel. In the western boundary current and most of the channel, the dominant balance in 8 is between isopycnal salinity advection and the surface salinity flux. Elsewhere, velocities are very small, so the dominant balance is between isopycnal diffusion and the surface salinity flux.

The idealized velocity fields for both narrow and wide sinking are shown in Figs. The resulting zonally averaged salinities are shown in Fig. In a configuration with two basins of different widths connected by a reentrant channel, sinking occurs in the narrow basin under zonally uniform forcing. Deep-water formation in the wide basin can be coerced by reducing the freshwater flux over the north of the wide basin and then we find that a stronger reduction is needed for larger ratios of basin widths.

Despite the reduction in freshwater flux for wide sinking, the salinity difference between the sinking basin and the nonsinking basin is smaller when sinking occurs in the wide basin. High salinity in the north of the sinking basin is always reinforced by a large cross-equatorial overturning cell, which transports salt northward across the equator: this is the salt advection positive feedback Stommel However, this feedback is less effective for wide sinking.

In particular, for zonally uniform salinity flux, we show that the wide sinking state is unstable. This is because higher salinity and therefore lower buoyancy is found at the surface in the north of the narrow basin, and freshwater is more efficiently advected southward by the subpolar wind-driven gyre in the wide basin.

The temperature advection negative feedback also plays a small role. When the width of the narrow basin is reduced further, keeping the width of the wide basin constant, the salinity difference between the basins increases, as does the preference for narrow sinking. A 2D advection—diffusion model shows that the advection of salinity in the upper branch of the 3D overturning is well represented by the velocity vertically integrated above the isopycnal that divides the upper and lower branch of the MOC.

The vertically integrated velocities show that there is a crucial difference in the sense of circulation on the western side of the SPG between the wide and narrow sinking basins. For narrow sinking, the western boundary current in the SPG is very weak, and for wide sinking it is strong and southward, advecting freshwater from the north, forming a halocline that is absent in the narrow sinking basin. This halocline is advected eastward by the southern branch of the SPG, suppressing deep-water mass formation.

We rationalize the difference between narrow and wide sinking by invoking the linear superposition of the western boundary velocities associated with the wind-driven SPG and with the MOC.

The latter is independent of the basin size, while the former is larger for a wide basin, and it prevails over the MOC in the wide sinking basin. We further emphasize the interaction of the gyral velocities with the MOC by contrasting the effect of the two velocity components in isolation. Advection by gyres-only velocities or MOC-only velocities leads to no preference for narrow sinking.

Our arguments work well in the idealized context of our model, with simple coastlines, flat bottom, and zonally uniform steady forcing. Thus, it is not clear how robust the narrow sinking preference is in more complex settings. It is difficult to compare observations of the SPG transport between the Atlantic and Pacific because most long-term observations are limited to m depth and hence include the upper branch of the MOC.

Deep-water formation largely occurs in marginal seas rather than in the open ocean, as it does in our model.

The W2N experiment described here was repeated with sills at the end of both of the continents and this led to no qualitative changes to the overturning. In this section, we use Cartesian coordinates, but the actual computations are in the spherical coordinates appropriate for the sector shown in Fig.

Sign in Sign up. Advanced Search Help. Journal of Physical Oceanography. Sections Abstract 1. Introduction 2. Vertically integrated velocities from in the 3D model b. Export References. Crossref Andrews , D. CO;2 false. Crossref Broecker , W. Crossref Bryan , F. Crossref Cessi , P.

Crossref Danabasoglu , G. Crossref Eden , C. Crossref Ferrari , R. Crossref Ferreira , D. Crossref Geay , J. Crossref Gent , P. Crossref Gnanadesikan , A. Crossref Gordon , A. Crossref Hewitt , C. Crossref Hughes , T. Crossref Huisman , S. Crossref Jones , C. Crossref Kamphuis , V. Crossref McCartney , M.

Crossref Nilsson , J. Crossref Redi , M. Crossref Reid , J. Crossref Schmitt , R. Crossref Schmittner , A. Crossref Seager , R. Crossref Stocker , T. Crossref Stommel , H. Crossref Talley , L. Crossref Wang , X. Crossref Warren , B. Crossref Weaver , A. Crossref Wills , R. Crossref Young , W. Crossref Zhang , R. Export Figures View in gallery Surface salinity anomaly, referenced to 35 psu, for zonally symmetric surface forcing in the top W2N geometry and bottom W3N geometry.

View in gallery As in Fig. View in gallery Meridional transport, zonally and vertically integrated within each sector above the isopycnal b m for top W2N and bottom W3N. View in gallery Streamfunction Sv associated with U gyre and V gyre. View in gallery top Zonally averaged salinity anomaly and bottom salinity anomaly when 8 uses the velocity associated with the streamfunction in Fig.

View in gallery a Zonally averaged salinity anomaly from the idealized 2D model using the velocity fields shown in Fig.

Close View raw image Surface salinity anomaly, referenced to 35 psu, for zonally symmetric surface forcing in the top W2N geometry and bottom W3N geometry. View raw image As in Fig. View raw image Meridional transport, zonally and vertically integrated within each sector above the isopycnal b m for top W2N and bottom W3N.

View raw image Streamfunction Sv associated with U gyre and V gyre. View raw image top Zonally averaged salinity anomaly and bottom salinity anomaly when 8 uses the velocity associated with the streamfunction in Fig. View raw image a Zonally averaged salinity anomaly from the idealized 2D model using the velocity fields shown in Fig. Chart I. Tracks of Centers of Anticyclones, December, Author: P. Previous Article. Editorial Type: Article. Jones 1 and Paola Cessi 1.

Article History. Download PDF. Full access. Corresponding author : C. Jones, csjones ucsd. Keywords: Meridional overturning circulation ; Ocean circulation ; Ocean dynamics. Introduction In the current climate system, deep water is formed in the North Atlantic but not in the North Pacific, resulting in a meridional overturning circulation MOC that transports heat northward everywhere in the Atlantic. The domain consists of two boxes of different widths connected by a reentrant channel occupying the southernmost The equation of state is linear, with the buoyancy described by.

Download Figure Download figure as PowerPoint slide. We frame the discussion of the meridional transport in terms of the residual overturning circulation ROC rather than the Eulerian circulation.

The ROC is defined as the time and zonally averaged meridional transport at constant buoyancy rather than at fixed depth levels. Thus, it measures the transport of buoyancy rather than the transport of volume. The ROC streamfunction is defined as.

The MITgcm solves the three-dimensional advection—diffusion equation: 3. A reduced description is obtained by integrating 7 vertically from the buoyancy surface b m to the sea surface and changing to buoyancy coordinates , following WRY12 details are in appendix A. Making the further assumption that S is vertically homogeneous above b m , we obtain.

Conclusions In a configuration with two basins of different widths connected by a reentrant channel, sinking occurs in the narrow basin under zonally uniform forcing. The 2D Advection—Diffusion Equation To simplify the advection—diffusion equation, we integrate 7 vertically from the depth to the surface, where b m is a constant. This gives. A substantial simplification of A3 and A4 is obtained by moving from Eulerian coordinates x , y , z , t to buoyancy coordinates , using the rules 21 to 24 in WRY Because , the horizontal derivatives can be moved outside the vertical integral giving.

Salinity Scaling for Advection by Gyres-Only Velocity Here, we illustrate how the difference in salinity between the SPG and subtropical gyre scales with the external parameters, assuming that the gyre velocities are horizontally nondivergent. With no diapycnal velocity, 8 becomes. View Table. Share Link Copy this link, or click below to email it to a friend.

Your current browser may not support copying via this button. AMS Publications. Get Involved with AMS. Affiliate Sites. Follow Us. Share Link Copy this link, or click below to email it to a friend. Your current browser may not support copying via this button. AMS Publications. Get Involved with AMS. Affiliate Sites. Follow Us. Contact Us. Email : amsjol ametsoc. Sign in to annotate. Delete Cancel Save. Cancel Save.