Distribution Of Nutrients 

 In The Weddell Sea 



February-March 1968 

 February-March 1969 



INTRODUCTION 



With the exception of the Ross Sea, the 

 Weddell Sea forms the largest indentation in 

 the roughly zonal coastline of the Antarctic 

 Continent. It is bounded to the west by the 

 Palmer Peninsula, to the east by Coats Land 

 and to the south by the Filchner Ice Shelf. 

 To the north, the basin is partially blocked by 

 part of the Scotia Ridge (fig. 1). 



Knowledge of the Weddell Sea has been lim- 

 ited to its periphery due to a perennial ice 

 cover. Except for a few observations that were 

 made along the drift tracks of the DEUTSCH- 

 LAND (1911-1912) (Brennecke, 1921) and the 

 ENDURANCE (1914-1916) (Deacon, 1937), 

 the waters of the central and western regions 

 of the sea remain unknown. From the scanty 

 data available, the Weddell Sea is recognized 

 as a major source of Antarctic Bottom Water 

 (Deacon, 1963). This Bottom Water is a major 

 constituent of the deep water found in the Pa- 

 cific, Indian, and Atlantic Oceans, and is im- 

 portant in deep-water circulation. 



Nutrient measurements in the Weddell Sea 

 are almost nonexistent. The work of Clowes 

 (1938) and others show that the amount of 

 phosphate, nitrate, and silicate in the Antarctic 

 surface waters rarely fall below the winter 

 maxima of temperate regions. A southward 

 moving, warm saline layer (>0. 2° C.>34.67''/on) 

 in the Antarctic region has the highest phos- 

 phate and nitrate concentrations. Silicate is 

 most abundant in the bottom waters. 



IWSOE '68 AND '69 



Scientists of the U.S. Antarctic Research 

 Program of the National Science Foundation 



have been interested for several years in ob- 

 taining oceanographic data in the Weddell 

 Sea. Under their coordination, the Interna- 

 tional Weddell Sea Oceanographic Expedition 

 (IWSOE) was formed as a cooperative multi- 

 disciplinary study of this unknown region. The 

 United States assigned the icebreaker USCGC 

 GLACIER (WAGE 4) as the research vessel 

 for the cruise. As a research platform, the 

 GLACIER was modified to accommodate five 

 laboratories, an expendable bathythermograph 

 launcher and recorder, a STD (salinity-tem- 

 perature-depth) system, a hydrographic winch, 

 a luffing crane, a PDP-8 computer, a precision 

 depth recorder, a satellite navigation system, 

 and an automatic picture transmission sys- 

 tem for recording satellite photos. 



The IWSOE was divided into diflTerent 

 phases. The primary objective of IWSOE '68, 

 the first phase, was to place four Norwegian 

 instrumented buoys on the Weddell Sea's con- 

 tinental slope to measure temperature and deep 

 currents believed associated with the forma- 

 tion of Antarctic Bottom Water (University 

 of Bergen). Other studies carried out for the 

 IWSOE '68 were primary productivity (Texas 

 A&M University), benthic zonation (Univer- 

 sity of Connecticut), sub-ice productivity (Uni- 

 versity of Miami, Florida), sedimentation 

 (Florida State University), trace elements 

 (Yale University), and seal populations (Uni- 

 versity of Minnesota). The Coast Guard Ocean- 

 ographic Unit obtained hydrographic data, 

 bottom photographs, cores, and nutrient sam- 

 ples. More detailed information on the pro- 

 grams can be found in the work of Elder and 

 Seabrooke (in press). 



IWSOE '69 was the second phase of the 



