SECT. 1] 



RADIOISOTOPES AND LARGE-SCALE OCEANIC MIXING 



99 



reservoir (often referred to as the "mixed layer") and a much larger deep 

 reservoir. In order to take into account the fact that the deep water masses 

 are fed by waters sinking in the polar regions, model II allows the deep water 

 to outcrop at the surface and model III incorporates a third well-mixed reservoir 

 at the end of the ocean. The world-ocean model, IV, separates the Atlantic 

 from the Pacific plus Indian Oceans incorporating two reservoirs of vertical 

 mixing, the Antarctic and the Arctic, at the ends of the two-layer oceans. The 

 Atlantic and Pacific-Indian Oceans interact only through the Antarctic 

 reservoir, the Arctic communicating only with the Atlantic (see Broecker 

 et al., 1960, for details of model IV). As each additional reservoir adds the 



WORLD-OCEAN MODEL (Cases EZ A and EZB) 



0.61 AU 



r "lo 



1 E 3 | J 3 



\ 0.I2A.U. 1 



0.23 A U 



J* .£"6 ,'e 



0.04 A.U.I 



I QUIA) 

 3 DU(B) 



35 DU.(A) 

 33DU.(B) 



5 V U (A) 

 0.45 VU (B) 



-" 



P.+J SURFACE 

 C/C A = 0.965 



Tco 2 



I 



TOS 



/SYRIA) 

 130YR(B^ 

 (24 YR?A) 

 l90 YR1BI 



PACIFIC + INDIAN 

 DEEP WATER 

 C/C A = 0.800 



6.1 VU (A) 

 5.8 V.U IB) 



T C o,=T D .s. = 800YR 



© | A. SURFACE 

 C/C A -- 0.960 



T . (6 YR(A) 

 'C°2" ll8YR(8) 

 006 VU (A) Tr , c -/l8YR(A) 

 QI7 VU 1BI 1D5 "l53YR(BI 



D 



ff 32 ff 53 



ANTARCTIC 

 OCEAN 

 C7C A 0BS.=0.885 

 C/C A CAL "0.880 



T C o 2 =70YR 

 T as .= 80YR 



* 



ATLANTIC 

 DEEP WATER 

 C/C A = 0.900 



2.0 V U. (A) 

 1.9 VU (B) 



Tco,= T D .s.= 650YR 



«46 



"ARCTIC" 



OCEAN 



C/C. 0BS.= 



0.970 

 C/C* CAL 



0.970 



0.12 V.U 



r c02 =30YR 

 T DS =40YR 



f, --I r -€ i --I- i =E A =I^=E 6 =I 6 = 22M/M 2 /YR 

 I, /3, = 4 8xlO l5 M/YR I 3 /» 3 =I.Ox I0 ,5 M/YR 

 J 4 /5 4 = 1.8 xlO l5 M/YR I 6 ^ 6 =03xl0 l5 M/YR 



ff, 3 =R 3 l = 1.6x10 M/YR 

 ff 23 =ff 32 = 2.5xl0 15 M/YR 

 *34=> ? 46 = ff 65 = ' ? 53 = l0xl0 l5 M/YR 



Fig. 6. Cases A and B differ in the thickness assigned to the surface ocean layer. Mixing 

 is assumed to take place only as indicated by the arrows, i.e. a cyclic flow in the 

 Atlantic and no direct mixing between the surface and deep reservoirs. The observed 

 14 C averages for the Antarctic and Arctic reservoirs, although unnecessary for the 

 rate calculations, are given for comparison with those demanded by the model in 

 order to satisfy the steady-state assumptions. 



necessity for further assumptions and parameters, the available isotope data do 

 not allow much more complexity than that in the present models. The numerous 

 oversimplifications are obvious when one compares the box models with the 

 water-mass structure of the oceans. 1 



Volumes and ocean-atmosphere interface areas have been assigned to each 



1 The surface -ocean 14 C/ 12 C ratios used in these models are about 10 per mil too high 

 resulting from an industrial CO2 correction applied at the time of writing (July, 1960). 

 This correction is now known to be considerably less than that applied. 



