Salinity depth profiles

Latitudinal variations in depth profiles of salinity in the (a) Atlantic, (b) Pacific, and (c) tropical oceans High-latitude salinities are given by the dashed lines. Source After Pickard, G. L, and W. J. Emery (1999). Descriptive Physicai Oceanography An Introduction, 5th ed. Butterworth-Heinemann, p. 52. 

Depth profiles of (a) salinity (%o), (b) dissolved oxygen (ml /L), and (c) percent saturation of dissolved oxygen in the Southeastern Atlantic Ocean (9°30 W 11°20 S). Samples were collected in March 1994. Dotted lines represent the curves generated by the one-dimensional advection-diffusion model (see text for details). The values of Dz, Vz, and J are the ones that best fit the data. Data are from Java Ocean Atlas (http /odf.ucsd.edu/joa). Values of percent saturation of oxygen less than 100 reflect the effects of aerobic respiration. Values greater than 100 indicate a net input, such as from photosynthesis. (See companion website for color version.)... 

Sampling sites are also referred to as station locations. For water column work, depth profiles are constructed from seawater samples collected at representative depths. Temperature and salinity are measured in situ with sensors. Remote-closing sampling bottles deployed from a hydrowire are used to collect water for later chemical analysis, either on the ship or in a land-based laboratory. The standard chemical measurements made on the water samples include nutrients (nitrate, phosphate, and silicate), dissolved O2, and total dissolved inorganic carbon (TDIC) concentrations. 

The study sites in the Chesapeake Bay are shown in Figure 2. Depth profiles were obtained at both the North and South Basin locations, where the water column was oxic throughout and had a fairly constant 02 concentration of 5 mg/L. The surface-water temperature, approximately 10 °C, remained constant at the South Basin throughout the water column while decreasing in the North Basin to slightly less than 9 °C in the lower 18 m of the water column. At both locations the surface water (approximately the top 10 m) was relatively fresh, with a saltwater wedge at the bottom. The surface-water salinity increased from the North Basin (10.6%o) to the South Basin (12.3%0). 

Exercise 9.7 The solubility of HC03 decreases or increases as a function of salinity Retrieve the answer from a close examination of the Salentine Peninsula data given in Table 9.3. From this set of data, is the HC03 confirming the conclusion discussed in the text concerning the observed composition changes in the depth profiles of the reported wells ... 

No consistent pattern for depth profiles of trace elements exists. Conservative elements trend with salinity variations provided they have no significant submarine sources. Non-conservative elements may exhibit peak concentrations at different depths in oxygenated waters as... 

The vertical structure of the ion composition in the relatively deep western basin is demonstrated by a typical example given in Table 4. The samples were collected in the deepest spot of the western basin (station A2) in October, 2005. Table 4 depicts a depth profile of the absolute and relative contents of the major ions. Perhaps, the most notable features of the profile are the cmitinuous decrease of the relative content of Ca " from 0.57% at the surface to 0.48% at the bottom, accompanied by an increase of the SO4 /CP mass ratio from 0.67 to 0.82. The corresponding vertical distributions are graphically illustrated by Fig. 3 (also shown in the figure is the salinity profile as revealed from CTD measurements). We note that similar vertical patterns are also evident in the profiles for other years (not shown here). For instance, in September of 2006, the relative mass content of Ca was 0.65% at the surface and 0.55% at the bottom, while the SO4 /CP mass ratio was 0.67 at the surface and 0.88 at the bottom. 

The distribution of a number of dissolved species (02, C-14, Ra-226, salinity) in the Central Pacific water column, at depths between 1 and 4 km, has been shown (11) to be consistent with a steady-state model of the water column in which the concentration-depth profiles are stationary and the concentrations at the boundaries 1 and 4 km are stipulated at their present values. The physical model of the water column is based on two transport mechanisms vertical eddy diffusion (eddy diffusion coefficient K — 1.3 cm2 sec"1) and upwelling of deep water (advection velocity U = 1.4 X 10 5 cm sec"1, or approximately 1 cm per day) (11). 

Figure 11 Depth profiles of (a) N2O concentration and (b) and (c) <5 0 of N2O at station ALOHA in the subtropical North Pacific (22° 45 N, 158° W) during four separate cruises. The solid line in (a) indicates theoretical saturation with atmospheric N2O at in situ temperatures and salinities. The minima in and <5 0 around 200 m are thought to be due to significant in situ production of N2O from nitrification. The broad isotopic maxima at depth are likely due to N2O consumption, perhaps in the denitrifying waters along the eastern Pacific margin. The filled squares at the top of (b) and (c) represent measurements of <5 N and <5 0 of atmospheric N2O during the Hawaii Ocean Time-series 76 cruise, and arrows indicate the range of historical measurements as of the late 1980s. Reprinted from Dore JE, Popp BN, Karl DM, and Sansone FJ (1998) A large source of atmospheric nitrous oxide from subtropical North Pacific surface waters. Nature 396 63-66.

An interesting vertical profile of the metabolite concentrations was observed the compounds showed a tendency to accumulate at the two-phase boundaries of air-freshwater and freshwater-saline water (the halocline). Thus, concentration maxima were observed at depths of 0 and 2 m (see Fig. 6.4.1) [6]. The observed distribution may result from either the physicochemical properties of these compounds (surface activity and hydrophobicity), or their formation at the interface due to increased biological activity. For the parent surfactants a similar but less pronounced vertical distribution pattern was observed (with maxima at 0 and 2 m of 17 and 9 xg L 1, respectively) [5],... 

However, salinity values are easily obtained with a salinometer (which measures electrical conductivity and is appropriately calibrated with standard solutions and adjusted to account for T effects). The salinity of seawater increases if the loss of H2O (evaporation, formation of ice) exceeds the atmospheric input (rain plus rivers), and diminishes near deltas and lagoons. Salinity and temperature concur antithetically to define the density of seawater. The surface temperature of the sea reflects primarily the latitude and season of sampling. The vertical thermal profile defines three zones surface (10-100 m), where T is practically constant thermoclinal (100-1000 m), where T diminishes regularly with depth and abyssal... 

In the solar evaporation ponds, salinities in the cores reached almost four times oceanic values. In these cores the concentration profile of bimane sulfide with depth also tracked that of methylene blue sulfide and bimane total reduced sulfur tracked DTNB. However, the difference between the bimane method and the other two methods is unacceptably large and suggests that there was some inhibition of the bimane reaction. Pore water samples which were diluted to normal seawater salinity with 200 mM HEPES buffer pH 8 were not inhibited. Dilution will of course lead to a loss of sensitivity for trace thiols. Another factor which can effect the yield of the bimane reaction is the unusual... 

The deep-water observations with conductivity, temperature, depth (CTD) profilers performed in the Black Sea during the past two decades allowed one to distinguish the near-bottom mixed layer (NBML). In Fig. 3b, we present profiles of the potential temperature (T ), salinity (S), and potential density (ct ) of the Black Sea waters in the layer from 1500 to 2100 m obtained by averaging of 46 CTD profiles observed in 1985-1992 in different regions of the deep-sea area. In all three profiles shown in Fig. 3b, a distinct upper boundary of the NBML is traced at depths from 1750 to 1800 m. Above it, up to a depth of 1700 m, one finds a layer with increased vertical gradients of T , S, and a with a thickness about 100 m it separates NBML from the deep stratified layer. 

In order to quantitatively estimate this statement, we carried out a statistical analysis of all the vertical temperature and salinity profiles available from January to March in 15 regions of the Black Sea with bottom depths greater than 50 m. In each of them, we determined the recurrences of two types of profiles with different depths of temperature minimums (1) in the UML and... 

The existence of a homogeneous bottom water mass - bottom convective layer (BCL) - at water depths below 1740-1800 m was first reported, based on detailed CTD profiling, by Murray et al. [42] and since then it has been intensively studied [43-52], Based on the data obtained in 1999-2002 in the north-eastern Black Sea, the bottom water mass was characterized by the following parameters potential temperature 0 = 8.883-8.888 °C, salinity S = 22.330-22.334psu, and potential density oq= 17.233-17.236kgm 3 [51]. On average, the water column below 500 m is about 0.01 °C warmer and 0.003-0.005 psu saltier in the western part than in the eastern part of the sea. Recent detailed studies have shown that not only the thermohaline characteristics, but also concentrations of several chemical species in bottom waters... 

One profile of particulate and dissolved 234Th between surface and 60 m depth was taken at each station in late April (Table 1). 238U activities increased with oceanic influence, in association with the salinity, from 2.10 dpm l-1 (Balsfjord) to 2.38 dpm 1 1 (Ullsfjord Table 2). Particulate... 

Thus, there are only a few data of dissolved oceanic NH3 available. (Reports on oceanic NH4 measurements are not considered here because without the knowledge of pH, water temperature, and salinity, the true concentration of dissolved NH3 remains speculative). Because the NH3/NH4 equihbrium strongly depends on the temperature, maximum NH3 concentrations are expected to occur in surface waters and should rapidly decrease with depth in association with temperature profiles in the subsurface and deep ocean. (Exceptions should occur in the few cases where subsurface NH4 maxima have been observed (Brzezinski, 1988 Gibb et al., 1999b)). Oceanic NH3 concentrations discussed in the fohowing paragraph are exclusively from the oceanic mixed layer. 

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