OCEANOGRAPHY OF THE WEDDELL SEA 



(1969— IWSOE) 



Introduction 



Deacon (1963) indicated that the Weddell 

 Sea is the largest source of Antarctic Bottom 

 Water (-0.4° C, 34.66%o). The generally ac- 

 cepted theory states that it is a mixture of 

 warm deep water and water formed on the 

 Antarctic continental shelf. The shelf water 

 gets its particular properties by convection due 

 to cooling and ice formation during the winter. 

 Owing to the nonlinear dependency of density 

 of seawater on temperature and salinity, the 

 processes determining the formation of Ant- 

 arctic Bottom Water are hampered or even 

 prevented until a certain stage has been 

 reached. The formation of Bottom Water may, 

 therefore, appear as a sudden flow, with a per- 

 ceptible current speed (Fofonoff', 195fi). 



In the summer of 1968, the icebreaker 

 USCGC GLACIER (WAGB-4), modified for 

 oceanographic research, became available for 

 the International Weddell Sea Oceangraphic 

 Expedition (IWSOE) under the coordination 

 of the National Science Foundation. The major 

 purpose of the expedition was to study the for- 

 mation of Antarctic Bottom Water. From the 

 data of IWSOE '68, Elder and Seabrooke (in 

 press) proposed a theory for the formation of 

 Antarctic Bottom Water in the summer. They 

 found the shelf water below 200 meters in the 

 southwest Weddell Sea to be sufficiently dense 

 to flow down the slope and mix with the warm 

 deep layer and form Antarctic Bottom Water. 

 Analysis of the data indicated that the dense 

 shelf water did not form at the air-sea inter- 

 face nor was it transported in from other 

 areas. Bathymetric data indicate it was not 

 water formed in the winter, trapped on the 

 shelf, and prevented from flowing off the shelf. 

 They concluded that the dense water was 

 formed on the continental shelf by contact 

 with the underside of the Filchner and Ronne 

 Ice shelves. 



The IWSOE '69 is the second phase of the 

 oceanographic program carried out in the 

 Weddell Sea and is a direct continuation of 

 IWSOE '68. The USCGC GLACIER, Captain 

 E. C. McCory, USCG, commanding, was as- 

 signed for the cruise. In addition to the al- 

 ready existing oceanographic facilities, a new 

 level luffing crane with a trawl winch was in- 

 stalled to give piston coring and heavier dredg- 

 ing capabilities to the ship. 



rVTSOE '69 Programs 



A number of institutions took part in the ex- 

 pedition conducting the following programs: 



University of Bergen: To evaluate the the- 

 ories of the formation of Antarctic Bottom 

 Water, Dr. Thor Kvinge of the University of 

 Bergen installed four current meter buoy ar- 

 rays on the continental shelf near 74° S., 

 40° W. during IWSOE '68 to measure currents 

 and temperature throughout the winter. One of 

 the primary objectives of IWSOE'69 was to re- 

 cover the current meters. 



The University of Connecticut: Dr. John S. 

 Rankin of the University of Connecticut stud- 

 ied the population density and diversity of the 

 deep sea benthos of the Weddell Sea using an 

 anchor dredge and an epibenthic sled. 



The University of Mirmesota: A program to 

 study the population dynamics of Antarctic 

 seals was conducted by Dr. Albert W. Erickson 

 of the Bell Museum of Natural History, Uni- 

 versity of Minnesota. The seal census was con- 

 ducted from the air by helicopter as well as 

 from the ship. Specimens were also captured 

 and blood samples taken for studies of phylo- 

 genetic and population of relationships. 



The University of California, Los Angeles: 

 Sedimentation processes operating in the Wed- 

 dell Sea were studied by Richard D. LeFever 

 of the Department of Geology, University of 

 California, Los Angeles. A modified Ewing pis- 



