372 REINERS 



and their reaction products interact with ozone, which is important in shielding 

 the earth's surface from the sun's ultraviolet radiation. Higher concentrations of 

 these gases may tend to lower stratospheric ozone concentrations. Such human 

 activities as concentrated cattle feeding and eutrophication of large water bodies 

 may raise these concentrations significantly. It seems conceivable, therefore, that 

 even without large numbers of high-flying supersonic aircraft, man may be 

 affecting stratospheric ozone levels. More insight into the natural cycle of CH 4 

 and the trace gases is required. 



Monitoring 



It is possible to monitor some of the trace gases on a worldwide basis by 

 satellite. There are programs under way to test the feasibility of measuring O3, 

 CH4, CO, and N 2 0. A particularly exciting possibility would be to obtain the 

 global distribution of CC» 2 with sufficient precision to allow development of 

 horizontal flux and global balance equations which in turn would allow us to 

 obtain a more accurate estimate of global biological activity. A feasibility study 

 of satellite surveillance was strongly recommended by the Brookhaven group. 

 See Refs. 14 and 15 for further discussion of this topic. 



The Ocean 



The ocean is unquestionably the largest pool for carbon and therefore an 

 important sink for excess atmospheric C0 2 . Because of its importance and 

 because of the complexity of the chemistry of the oceans, no program of 

 research on the global carbon cycle should be attempted without the aid of 

 marine geochemists. Unfortunately material for this report was prepared without 

 the benefit of direct consultation with such a person, and the following 

 treatment on oceans is developed almost entirely from Broecker, Li, and Peng 1 6 

 and Broecker's presentation at the Brookhaven Symposium. 



The Surface Layer 



The surface layer of the ocean is relatively warm and well mixed to a depth 

 of about 70 m and overlies a deep layer of lower temperature. A thermocline of 

 about 1000 m thickness lies between these layers and acts as a barrier to mixing. 

 About 10% of the ocean's surface area does not have an upper, warm layer, so 

 that the atmosphere is in direct contact with the deep layer in these "outcrop" 

 regions. 



The CO2 gas exchange between the surface layer and the atmosphere is 

 related to the partial pressure of C0 2 of the atmosphere and the concentration 

 of dissolved inorganic carbon in the ocean. Concentration of dissolved carbon is 

 related, in turn, to equilibria with bicarbonate and borate ions. Broecker et al. 1 

 calculated that the oceanic surface layer contained about as much carbon as the 

 atmosphere and that, with an increase in atmospheric C0 2 , the surface layer 



