SECT. 1] 



RADIOISOTOPES AND LARGE-SCALE OCEANIC MIXING 



TWO LAYER MODEL (Cases IA and IB) 



l£i ,1. 



97 



© 



SURFACE OCEAN 

 C/Ca -- 0.957 



T, 



■j 



Td.s. s { 



9 YR(A) 

 25 YR (B) 

 45 YR (A) 

 140 YR (B) 



DEEP OCEAN 

 C/C A - 0.800 



T C o 2 = T .s. = 1650 YR 



I D.U.(A) 

 3 D.U.(B) 



35 D.U. (A) 

 33 D.U(B) 



f| =I| = 22M/M 2 /YR ff 2 l = ff l2 = 5M/M 2 /YR 



Fig. 2. Cases A and B differ in the thickness assigned to the mixed layer. The 14 C values 

 for each reservoir are given as fractions of the pre -industrial atmospheric 14 C/ 12 C 

 ratio and are based on the average of the available measurements. The transfer rates 

 are computed assuming steady state. t C02 and t d .s. refer to the mean residence times 

 for CO2 and for dissolved solids. 



£2 \h 



0.09A.U. 



OUTCROP MODEL (Cases II A and IB) 

 _T__ O60 A.U. 



© I 



0.15 VU. 



SURFACE OCEAN 

 C/C A -- 0.970 



r - [ IC 

 To.s. - [ 



YR (A) 



YR (B) 



00 YR (A) 



YR(B) 



DEEP OCEAN 

 C/Ctc 0.800 



^COs 



r i85 



850 YR(A) 

 (B) 



. {4600 YR(A) 



(B) 



DU 



35 D.U 



E|=I| 



■{ 



22 M/M'/YR (A) 



M/M 2 /YR (B) 



22 M/M 2 /YR (A) 



50 M/M 2 /YR(B) 



■{ 



2.3 M/MVYRIA) 

 (Bi 



Fig. 3. Cases A and B differ in the value assigned to the ratio of the ocean-atmosphere 

 exchange rate for the polar ocean to that for the surface ocean. Case B yields negative 

 values of ~Ryi and i?2l indicating that the rate of 14 C addition through the deep- 

 water outcrop is too great to allow the low 14 C/ 12 C ratios observed in the deep sea. 

 Thus, if this model is to be retained, either the contrast in the outcrop-mixed layer 

 exchange rate or the area of outcrop must be considerably smaller than those adopted 

 in Case B. 



