OCEANOGRAPHY OF THE WEDDELL SEA 



January - March 1968 



Introduction 



The importance of the oceanographic pro- 

 cesses of the Weddell Sea and the need for 

 their study has long been recognized. This 

 area is generally believed to be the source of 

 most of the Antarctic Bottom Water that flows 

 northward into the ocean basins. There are 

 varying opinions on the northward extent of 

 Antarctic Bottom Water. Defant (1961) indi- 

 cated that it can be traced to 25 °N. in the 

 Pacific and 8° N. in the Atlantic while Dietrich 

 (1965) traced it to as far north as 50° N. 

 latitude in the Pacific and 45° N. latitude in 

 the Atlantic. 



Just as the importance of the oceanographic 

 processes of the Weddell Sea has long been 

 recognized, the difficulty of such a study has 

 also been apparent. Prior to the International 

 Geophysical Year (IGY) the Weddell Sea was 

 only crossed five times; by James Weddell in 

 1823, by Sir James Clark Ross in 1843, by W. 

 S. Bruce in 1904, by Wilhelm Filchner in 1911, 

 and by Ernest Shackleton in 1915. (Klepikov 

 1963). The latter two accounts especially in- 

 dicate the treachery of the Weddell Sea since 

 both ships became ice-bound for prolonged 

 periods of time and, in the case of Shackle- 

 ton's voyage, resulted in the complete destruc- 

 tion of ENDURANCE. The sheer heroism of 

 the account of the survival of Shackleton and 

 his crew is unequalled outside of fiction. 



Even with modern icebreakers, an exten- 

 sive area in the Western Weddell Sea remained 

 unstudied. In the early 1960's several methods 

 of observation were considered. One idea was 

 to initiate a program similar to the Arctic's 

 Operation Ski Jump. Upon further investiga- 

 tion, this proved to be impractical owing to 

 the remote location of the Weddell Sea. The 

 flight time from an existing air support site 

 or the practical problems in setting up a tem- 

 porary site were formidable. More important, 

 ice conditions in the Weddell Sea are not suit- 



able for even the most daring aviator to at- 

 tempt landing; hence plans for an aircraft 

 supported oceanographic program were aban- 

 doned. 



Despite obvious difficulties, the National 

 Science Foundation included the study of the 

 oceanography of the Weddell Sea in its long 

 range plans. The need for such a program was 

 also evident to the U.S. Coast Guard and fit 

 into its expanded oceanographic mission. Con- 

 sequently, owing to the combined needs of the 

 National Science Foundation and the U.S. 

 Coast Guard, it was decided to modify USCGC 

 GLACIER (WAGB 4), the largest of the na- 

 tion's icebreakers, to make it capable of carry- 

 ing out an extensive oceanographic program. 

 Modifications made prior to IWSOE '68 for 

 Antarctic oceanographic operations included 

 addition of five oceanographic laboratories, 

 two oceanographic winches, a level luffing 

 crane for over-the-side work, a salinity- 

 temperature-depth recording system, an 8K 

 memory computer, and standard oceanogra- 

 phic laboratory equipment. Prior to IWSOE 

 '69 an additional winch and luffing crane were 

 installed to give USCGC GLACIER piston 

 coring and heavier dredging capacity. These 

 modifications made meaningful, well-rounded 

 oceanographic programs possible. Figure 1 

 shows the alterations accomplished on USCGC 

 GLACIER. 



Two items which contributed greatly to the 

 success of IWSOE '68 were satellite photo in- 

 formation and satellite navigational equip- 

 ment. Navigation in the Weddell Sea is 

 extremely difficult and inaccurate. No naviga- 

 tional aids are available and celestial naviga- 

 tion is hampered by skies that are generally 

 overca.st, coupled with an indistinct horizon 

 due to the presence of ice. These conditions 

 make the calculations of even the best of 

 navigators subject to considerable uncertainty. 



