EXCHANGE OF MATTER BETWEEN ATMOSPHERE AND SEA 421 



graphic Institution (personal communication) performed a field 

 experiment to study the rate at which excess carbon dioxide was 

 given off from sea water. From his data the corresponding transport 

 velocities were calculated as from 10-^ to 4 X 10-^ cm-sec~^ These 

 figures certainly agree well with those given above. 



We may also compare the estimated transport velocity with the 

 rate of exchange of oxygen studied by Red field (1948) in the Gulf 

 of Maine. He obtained different values for summer and winter, 

 and if his values are converted into corresponding transport velo- 

 cities, they become 3.6 X 10~^ cm-sec~^ in summer and 1.2 X 10~- 

 cm-sec ^ in winter. With a ratio of winter to summer areas of 1 

 to 2.5, the average transport velocity becomes 6 X 10~^ cm-sec~\ 

 which, if applied to the exchange of carbon dioxide in the atmos- 

 phere, will give a residence time of about 3.5 years. This time is in 

 no way unreasonable. It therefore seems likely that in the exchange 

 of carbon dioxide between atmosphere and sea the rate of hydra- 

 tion of carbon dioxide is slow enough to prevent any exchange be- 

 tween atmospheric carbon dioxide and bicarbonate and carbonate 

 species at the surface. The exchange between the new carbon dioxide 

 obtained from the atmosphere and the bicarbonate and carbonate 

 takes place later when the original surface layer has been mixed 

 into subsurface water. 



It is interesting to note the much greater exchange rate in winter. 

 For oxygen this is nearly four times as great as the summer rate. 

 For carbon dioxide one might expect a still greater difference be- 

 cause of the greater variation of solubility of carbon dioxide with 

 temperature. A great part of this difference between summer and 

 winter is due to the turbulent mixing conditions and is reflected 

 completely in the computed transport velocities. Redfield (1948) 

 suggested that the larger winter values were primarily due to more 

 frequent storms. It is also possible that the instability caused by 

 cooling contributes substantially. This difference in transport 

 velocities in the sea has also some bearing on the present carbon 

 dioxide problem. Any model of the carbon dioxide exchange in- 

 volving warm and cold surface waters of the sea must consider the 

 greater rates of exchange anticipated in areas of cold surface waters. 

 Eriksson (1959a) has recently computed the meridional transport 



