FACTORS CONTROLLING C0 2 CONTENT 

 IN THE OCEANS AND ATMOSPHERE* 



WALLACE S. BROLCKERf 



Lamont — Doherty Geological Observatory of Columbia University, 



Palisades Park, New York 



This is a summary of what I think to be factors controlling the long-term carbon 

 content of the atmosphere and the ocean, and I will begin with the grand carbon 

 cycle (Fig. 1). We know that the main supply of carbon to the earth's surface is 

 by erosion and metamorphism of sediments. The contribution of new carbon 

 coming in from outer space or from deep in the mantle is probably very small. 

 There are roughly 10 moles of carbon per square meter of ocean surface stored 

 in sediments in the form of calcite, dolomite, and organic material which oil 

 geologists call kerogen; in the ocean we have about one-thousandth as much. 

 This carbon is being run around the ocean-sediment cycle at something that 

 approaches steady state. At any given time one part in one thousand of the 

 carbon is in the ocean— atmosphere system, and the rest is in sedimentary rocks. 

 The distribution between these two reservoirs is determined by the time 

 constants for the processes which destroy sediments and for those which remove 

 things from the ocean. We know that the time constant for destruction of 



* Author's Note: This paper is an edited transcript of my oral presentation. If the reader 

 wishes a more detailed presentation of the ideas briefly outlined here, I suggest the 

 following papers. First a treatment of the ocean chemistry control model is given in an 

 article entitled "A Kinetic Model for the Chemical Composition of Seawater" published in 

 Quaternary Research, 1: 188-207 (1971). The means by which paleoocean chemistry might 

 be read from sediments are outlined briefly in this same paper and in more detail in a paper 

 entitled "Calcite Accumulation Rates and Glacial to Intcrglacial Changes in Oceanic Mixing" 

 that appears in a volume entitled The Late Ceuozoic Glacial Ages, pp. 239-265, Yale 

 University Press, New Haven, Conn., 1971. Finally the East Pacific Rise study is in press in a 

 'SEPM volume, suggested title Studies in Paleo-Oceanogmphy, William Hay (I'd.). 



tLamont — Doherty Geological Observatory Contribution No. 1976. 



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