systematic variations in the Ca** fraction of 

 sea salt show up clearly and quantitatively. 

 Ca** profiles can be drawn and dissolution 

 rates for calcium carbonate calculated. 



Stable Isotopes — Variations in the C'^/C'- 

 ratio of bicarbonate carbon are measured on 

 a large suite of deep water samples. Shifts 

 toward C'^-depleted carbon are used to evalu- 

 ate the oxidation of detrital organic matter in 

 deep water. Variations in the 0'**/0'" ratio of 

 dissolved oxygen are also being determined 

 because they reflect the same oxidation proc- 

 ess. Atmospheric water vapor variations in 

 D/H and 0'**/0'" ratios are of great interest 

 for studies of the air-sea exchange of moisture 

 and for estimating the latitudinal transport of 

 atmospheric water. 



Preparatory Cruises 



Since the inception of the program, six in- 

 tercalibration and testing expeditions were 

 mounted, in which detailed vertical profiles 

 were obtained: GEOSECS-I in the North Pa- 

 cific, September 1969; GEOSECS-II in the 

 North Atlantic, August 1970; leg 15 of S.I.O. 

 Antipode Expedition in the South Pacific, 

 August 1971; and the Gogo I and II reoccupa- 

 tions of GEOSECS-I in November 1971 and 

 April 1972. GEOSECS-II was reoccupied by 

 Knorr in July 1972. Of necessity, most of the 

 work on these stations has involved intercali- 

 bration studies by U.S. and foreign investiga- 

 tors and extensive testing of equipment and 

 techniques. Nevertheless, the results to date 

 are important in their own right because of 

 the detailed vertical sampling and the associa- 

 tion of many types of measurements on the 

 same water masses. The GEOSECS-I results 

 were reported in the Journal of Geophysical 

 Research, 75: 7696 (1970). In Earth and Plane- 

 tary Science Letters, 15 (1972), some of the 

 initial results are reported from Leg 15 of the 

 S.I.O. Antipode Expedition. These include: 

 The current status of the measurement of 

 barium, an element of great importance be- 

 cause of its relationship to radium and sili- 

 con; recent developments in the extraction 

 of Si^- and Ra^^* on synthetic fibres; and 

 the work done at the North Atlantic Station, 

 GEOSECS II. 



The Atlantic Cruise 



The GEOSECS cruise track for the entire 

 Atlantic Ocean was completed in March 1973 

 (Figure 7). The scientific and technological 



cm 



Him 



ilSOUTH ^ 

 SANDWICH ISLAND 

 SOUTH ORKNEY ISUND 



Figure 7 



15 



