Atlantic Ocean alkalinity

However, a few examples of metasomatism and chemical enrichment by alkaline, deep-seated melts have been described, notably in the St. Paul s Island oceanic peridotites, in the Atlantic Ocean (Roden et al., 1984) and in the Lherz orogenic massif and neighboring massifs such as Caussou, in the Eastern Pyrenees (Fabries et al., 1989 Bodinier et al., 1988, 1990). 

Salinity-normalized (S = 35) total alkalinity. Ay n> versus salinity-normalized dissolved inorganic carbon, DICn, for the world s ocean. Data are for the deep ocean at depths >2.5 km except for the section labeled North Atlantic Shallow," which is 100-1000 m in the North Atlantic Ocean. Lines indicate different DICn At.n ratios. (See Plate 2.)... 

Brewer, P. G., Bradshaw, A. L. Williams, R. T. 1986. Measurements of total carbon dioxide and alkalinity in the North Atlantic Ocean in 1981. In Reichle, D. (ed.) The Global Carbon Cycle Analysis of the Natural Cycle and Implications of Anthropogenic Alterations for the Next Century. Springer-Verlag, Berhn, 358—381. 

Hoffman et al. (1974) found the same procedure applicable to data obtained from measurements on board of ships in the central Atlantic Ocean. Table 7-15 includes mean (X)/(Na) ratios from their work. Shown in parentheses are the values derived from the slopes of regression lines. They are distinctly lower than the averaged data. Hoffman et al. (1974) measured also the abundance of iron in the aerosols. Since the samples were taken in a region partly affected by fallout from the Saharan dust plume, iron serves as a convenient indicator for the contribution of material from continental sources. Not surprisingly, the enrichment of the elements Mg, Ca, K, and Sr was well correlated with the iron content. The (X)/(Na) ratios approached those of sea water only when the Fe concentrations were very low. These results demonstrate that materials from both marine and crustal sources are present over the open ocean. In addition, they provide some verification for the existence of a tropospheric background aerosol having the continents as a source, and they confirm the absence of a significant fractionation of alkali and alkaline earth elements in the production of sea salt. 

They suggested that most of the carbonate dissolution in the deep ocean (Fig. 9.5) occurs within the sediments (85 %). The extension of their results from Pacific and Indian Ocean to the Atlantic Ocean leading to 120 10 molyr of global dissolved carbon fluxes from sediments may, however, be critical because of the completely different deep-water conditions in the Indo-Pacific and the Atlantic. Deep ocean waters in the Indian and Pacific Oceans are known to be much older and depleted in CO implying that a much higher proportion of calcite dissolution contributes to the total alkalinity input there. However, despite this problem of different bottom-... 

Fig. 10-20 Observed depth profiles of (a) phosphate, (b) dissolved inorganic carbon (TC), (c) alkalinity (TA), and (d) oxygen for the Atlantic, the Indian, and the Pacific Oceans as indicated. Data are from GEOSECS stations within 5° of the Equator in each ocean. (Modified from Baes et al. (1985).)...

Fig. 11-9 (a) The vertical distributions of alkalinity (Aik) and dissolved inorganic carbon (DIC) in the world oceans. Ocean regions shown are the North Atlantic (NA), South Atlantic (SA), Antarctic (AA), South Indian (SI), North Indian (NI), South Pacific (SP), and North Pacific (NP) oceans. (Modified with permission from T. Takahashi et ah, The alkalinity and total carbon dioxide concentration in the world oceans, in B. Bolin (1981). Carbon Cycle Modelling," pp. 276-277, John Wiley, Chichester.)... 

Figure 4.7. The mean vertical distribution of (a) alkalinity and (b) total CO2 concentration normalized to the mean world ocean salinity value of 34.78. NA = North Atlantic, SA = South Atlantic, NP = North Pacific, SP = South Pacific, NI = North Indian, SI = South Indian, and A A = Antarctic region. (After Takahashi etal., 1980b.)...

Also, inorganic P is not the only P source for Trichodesmium in the open ocean (MulhoUand et al, 2002). Trichodesmium produces alkaline phosphatase (APA), which cleaves P04 from dissolved organic P compounds to provide an additional P source to the organism. APA activity in natural populations of Trichodesmium can indicate P stress to some degree. APA was much higher in the North Atlantic, where inorganic P concentrations are extremely low, than off the northern coast of... 

Weaver, B., Wood, D., Tarney, J. Joron, J. L. 1987. Geochemistry of ocean island basalts from the South Atlantic Ascension, Bouvet, St Helena, Gough and Tristan da Cunha. In Upton, J. F. B. (ed.) Alkaline Igneous Rocks. Geological Society, London, Special Publications, 30, 253-267. 

Both Die and Ax increase from surface waters to the deep Atlantic, Antarctic and Pacific Oceans as one follows the route of the ocean conveyor helt (Fig. 1.12). Along this transect pH changes from about 8.2 in surface waters to 7.8 in the deep Pacific Ocean, and CO3 decreases from nearly 250 geq kg to less than a third of this value, 75 geq kg. The reason for this change has to do with the ratio of the change in Aj and DIG in the waters and is discussed in the final section of this chapter. Notice that the contribution of the nutrients Si and P to the total alkalinity is only between 0 and 5 geq kg or at most 0.2% of the total alkalinity. Although Si concentrations are much greater than those of P, the two nutrients have nearly equal contributions to the alkalinity (Table 4.4) because the pK values for two phosphate reactions are closer to the pH of seawater than is the pK for sfiicate (see Table 4.1). 

Cross sections of total alkalinity (A) and DIG (B) in the Atlantic, Indian and Pacific Oceans. Modified from the figure in Key et al. (2004). 

Figure 13. The vertical distribution of alkalinity (a) and dissolved inorganic carbon in the World s Ocean. Ocean regions are shown as NA (North Atlantic), SA (South Atlantic), AA (Antarctic). SI (South Indian), Nl (North Indian), SP (South Pacific) and NP (North Pacific) (Molten, 1992).

Fig. 5.21d shows the seasonal variability of titration alkalinity (TA) measured in the mixed-layer at SEATS site (South-East Asian Time-series Study, 18°15 N, 115°35 E). TA values vary from 2,190 to 2,220 j,mol/kg with higher values in January, July, and September and lower values in March, April, and November. The observed seasonal oscillation of TA is thus controlled primarily by the same factors affecting salinity. A similar relationship between TA and salinity is also documented at BATS (Bermuda Atlantic Time-series Study, 31° 50 N, 64° 10 W) and HOT (Hawaii Ocean Time-series, 22°45 N, 158°00 W) sites (Bates et ah, 1998). However, as revealed in Fig. 5.21e, NTA remains variable throughout the year, suggesting the potential...

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