Pacific Ocean alkalinity

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).)...

Vertical concentration profiles of (a) temperature, (b) potential density, (c) salinity, (d) O2, (e) % saturation of O2, (f) bicarbonate and TDIC, (g) carbonate alkalinity and total alkalinity, (h) pH, (i) carbonate, ( ) carbon dioxide and carbonic acid concentrations, and (k) carbonate-to-bicarbonate ion concentration ratio. Curves labeled f,p have been corrected for the effects of in-situ temperature and pressure on equilibrium speciation. Curves labeled t, 1 atm have been corrected for the in-situ temperature effect, but not for that caused by pressure. Data from 50°27.5 N, 176°13.8 W in the North Pacific Ocean on June 1966. Source From Culberson, C., and R. M. Pytkowicz (1968). Limnology and Oceanography, 13, 403-417. 

Betzer et al. (1984, 1986) studied the sedimentation of pteropods and foraminifera in the North Pacific. Their sediment trap results confirmed that considerable dissolution of pteropods was taking place in the water column. They calculated that approximately 90% of the aragonite flux was remineralized in the upper 2.2 km of the water column. Dissolution was estimated to be almost enough to balance the alkalinity budget for the intermediate water maximum of the Pacific Ocean. It should be noted that the depth for total dissolution in the water column is considerably deeper than the aragonite compensation depth. This is probably due to the short residence time of pteropods in the water column because of their rapid rates of sinking. 

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). 

Depth profiles of total alkalinity (Aj) in the Atiantic, Antarctic, indian and Pacific Oceans. Piotted in Ocean Data View, using data from the e-WOCE compiiation. 

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. 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.)...

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).

It is veiy interesting to note that many of the more recently obtained calculations agree very much with those of Berelson et al. (1994) who calculated the benthic alkalinity input to the deep ocean for the Pacific and the Indo-Pacific (Table... 

In Figure llA the upper 1000 m of the Pacific WOCE A " C section shown in Figure 5C is reproduced. Figure IIB shows the estimated natural A " C using the potential alkalinity method. The shape of the two contour sets is quite similar however, the contour values and vertical gradients are very different, illustrating the strong influence of bomb-produced radiocarbon on the upper ocean. The... 

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