ferent oceans and whether other sources 

 exist are not known. GEOSECS research con- 

 tributes substantially to the understanding of 

 these processes. 



Although a crude idea exists of the average 

 effective speed of chemical constituent diffu- 

 sion processes, little is known of the vertical, 

 horizontal or time-dependent variations, or of 

 the source of energy that drives the turbu- 

 lence. Radionuclides such as strontium, 

 cesium, tritium and man-produced carbon-14, 

 recently introduced to the surface waters as 

 fallout, are measured by the GEOSECS 

 scientists. They are used to deduce the rates 

 of downward mixing from the surface to 

 intermediate depths, thus determining (quan- 

 titatively) the rates of turbulent diffusion and 

 downwelling in various oceanic situations. 



Interpretation of radioisotope tracer data 

 in relation to the rate of vertical mixing re- 

 quires exact knowledge of the concentrations 

 of the corresponding stable isotopes. For 

 example, the release in deep water of C'^Oi; 

 by the decay and sinking of biological parti- 

 cles is correlated with the release of stable 

 CO2 which can be estimated from measure- 

 ment of dissolved total CO-, alkalinity and pH, 

 or any two species within the oceanic carbon- 

 ate system. Measurements of the concen- 

 trations of the natural radioactive isotopes 

 radium-226, silicon-32 and cosmic-ray-pro- 

 duced carbon-14 in the deep and bottom 

 waters of the ocean will improve knowledge 

 of advection and turbulent diffusion. These 

 convenient nuclear clocks are being used to 

 determine the age of water masses in much 

 the same way that carbon-14 is used to mea- 

 sure the age of solid objects. The potential 

 of these new methods for studying the sea 

 has only begun to be realized. 



GEOSECS scientists are making detailed 

 measurements of oceanic constituents at all 

 depths along north-south sections from the 

 Arctic to the Antarctic, to provide, for the first 

 time, a set of physical and chemical data 

 measured on the same water samples. In addi- 

 tion to establishing geochemical baselines, 

 these data will provide input for quantitative 

 studies of oceanic mixing and for descriptive 

 models of ocean circulation. 



Sampling Plan 



The U.S. portion of the project calls for the 

 occupation of oceanographic stations along 



survey tracks which follow the approximate 

 trajectories of the bottom water currents in 

 the Atlantic and Pacific Oceans. The U.S. 

 schedule of cruises includes the Woods Hole 

 Oceanographic Institution's R/V Knorr run- 

 ning the Atlantic track during July 1972-April 

 1973 and Scripps Institution of Oceanogra- 

 phy's R/V MelvilJe running the Pacific track 

 during August 1973-May 1974 (Figure 3). 

 Cruises by ships of West Germany, Japan and 

 other nations add supplementary sections. 



At each U.S. station vertical profiles of 

 50 samples are taken, and at alternate stations 

 large samples are taken at 16 to 20 depths for 

 measurements of trace constituents and low 

 concentration radioisotopes. The vertical 

 spacing of all these samples is guided by con- 

 tinuous on-station recording of temperature, 

 salinity and dissolved oxygen. Particulate 

 matter is collected at all depths, and dissolved 

 gases are extracted from the sea water for 

 onboard analysis by gas chromatography. 

 Much of the analytical work is done on the 

 ships during the expedition, with the balance 

 to be done in the laboratories of participating 

 geochemists throughout the world. For future 

 work a library of water samples is maintained 

 at Woods Hole. 



Shipboard Laboratory Analyses 



Since project success depends upon the 

 precise and rapid measurement of several 

 ocean variables automated analytical systems 

 are used aboard ship for many of the routine 

 chemical measurements. All physical and 

 chemical measurements made at sea are fed 

 into the shipboard computer. Data logged 

 from principal and auxiliary sources are 

 brought together in a real-time system to com- 

 pute final values of all parameters. A large 

 proportion of the data is, therefore, available 

 for evaluation by the Chief Scientist while 

 still on station (Figure 4). 



The computer console consists of: Analogue 

 tape recorder for recording signals from the 

 in situ package, trouble-shooting equipment, 

 real-time clock, trigger controls for the rosette, 

 cathode ray display units, typewriter terminal, 

 hard copy reproduction unit for printing 

 cathode ray tube displays and an X-Y print 

 plotter. 



The following shipboard systems are auto- 

 mated or partially automated and interfaced 

 with the computer: Salinometry, alkalinity- 



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