Ecoinformatics Problems of the World Ocean - New Ecoinformatics Tools in Environmental Science: Applications and Decision-making - page 272

Eriksson (1963) found out that a 1 % increase of alkalinity causes a 2.26 %
decrease of the CO 2 partial pressure in the atmosphere and a 98 % reduction of total
CO 2 supply in the hydrosphere. When there is no external input of Ca into the
hydrosphere, a 1 % increase of alkalinity causes an increase of the rate of CaCO 3
deposition and the total alkalinity decreases by 0.92 %. Thus, a 1 % increase of the
water alkalinity is equivalent to an increase of pH by 0.5.
An equilibrium between various components of the hydrospheric carbonate
system depends on temperature and pressure, a combination of which correlates
with pH so that at a given temperature and pressure the equilibrium is a function of
only pH = lg[H + ]. The effect of temperature on pH in the

− first approximation can

be described by the Merrey law (Ivanov 1978): ʔ pH = − 0.0111 ʔ T, valid at pH ∈

30] o C, and salinity from 10 to 40 o / oo . The dependence of pH on
pressure p c follows the Buch-Grippenberg law: pH = d

[7.5, 8.4], T ∈ [1

-

ʔ p c , where, on the average,

d = 0.0254. A more accurate presentation of this law is given in Table 4.3 .

The connection between the equilibrium condition of CO 2 exchange and pH on the
atmosphere-ocean border is such that when the CO 2 pressure in the atmosphere
reaches 330

−

10 − 6 atm, equilibrium occurs at 20 C for

pH = 8.11. For a lower pH value, the ocean assimilates CO 2 , while for a higher pH
value the ocean emits CO 2 . Hence, the structure of the ocean carbonate system should
be thoroughly studied in order to describe the functions of the

× ° C for pH = 8.16 and at 0 °

uxes H 2 andH 3 on the

fl

atmosphere-ocean border. A simpli fluxes is usually based on

the comparison of the partial pressures of CO 2 in the atmosphere and in the ocean.
According to the data in Alexeev et al. (1992), the

ed description of these fl

uxes H 2 and H 3 fl are well

approximated by the function H i p c ) 1/2 , where p a and p c are the partial

pressures of CO 2 in the atmosphere and in the ocean, respectively. The partial pressure
of CO 2 in the atmosphere at the level of the ocean can be calculated using the formula:

= k i (p a −

421542 10 18 M C 273

p a ¼ 0 : ð : 15 þ T Þ;

where M C is the CO 2 mass in tons and T is the air temperature in C.

According to Bjorkstrom (1979), the functional dependence of p c on the
parameters of the ocean carbonate system can be presented in the form of
p c = [CO 2 ]/K 0 . From the condition of chemical equilibrium, according to the
Eqs. ( 4.4 ) and ( 4.5 ), it follows:

°

X C

¼H þ

½ CO 2 ½ = a ;

where a =[H + ] 2 +[H + ]K 1 + K 1 K 2 , ʣ C = C U /W U , W U is the volume of an elementary

reservoir.

Table 4.3 Empirical dependence of pH on atmospheric pressure
pH at atmospheric pressure 7.5 7.7 7.9 8.1 8.3

D pH with pressure increasing by 1,000 dbar − 0.035 − 0.028 − 0.023 − 0.021 − 0.02