ATMOSPHERIC CARBON DIOXIDE AND RADIOCARBON: 



93 



where P m0 and 2C are preindustrial values of P m and EC. The evasion factor 

 depends on the dissociation quotients of carbonic acid, boric acid, and water in 

 seawater, the hydrogen-ion concentration, the total boron concentration, EC, 

 and the alkalinity. For an average surface water (Appendix D), all these factors 

 remain unchanged when C0 2 is added to seawater except hydrogen-ion 

 concentration and EC. The alkalinity is constant because total ionic charge is 

 unaffected by adding or removing the uncharged species C0 2 . For any given 

 value of EC, the hydrogen-ion concentration in average surface water is found 

 using the equations in Appendix D, and then £ is evaluated. At the beginning of 

 the industrial era, the evasion factor was identical to the factor 

 d(ln P m )/d(ln EC) of Bolin and Eriksson. 3 If industrial C0 2 production 

 continues to increase, however, £ will rise with P m according to the relation 

 shown in Fig. 3. At the same time the short-term capability of the oceans to 

 absorb C0 2 from the atmosphere will diminish. 



40 — 



30 



20 — 



10/ 



p /p 



r m' r mo 



Fig. 3 Variation in evasion factor (£) for average ocean surface water as a 

 function of C0 2 partial pressure relative to preindustrial times. (The date 

 arrows are for the preferred model discussed later in text for which /3 = 0.44, 

 T am = 7 years, r dm = 1500 years, and N mo /N ao = 4.) 



