Background Information

The concern over rising atmospheric CO₂ levels due to human activities and the proposed CO₂-induced global warming has amplified the need to understand the role of the ocean in the carbon cycle. The oceans are believed to act as a sink for human-induced, or "excess" CO₂. Most of our knowledge of the distribution of excess CO₂ in the oceans has come indirectly from the study of proxy data, namely the two major transient tracers, tritium and ¹⁴C (Chen, 1984).

In order to gain an understanding of CO₂ transport in quantitative terms, direct measurements of oceanic CO₂ transport are needed. Studies by Brewer (1978), Chen and Millero (1978), and Rodman and Chen (1978), Chen and Millero (1979), Chen and Pytkowicz (1979), Chen (1982a,b), and Chen et al., (1982) may be useful in this respect. These studies were mostly based on data collected in the Southern Ocean. Deep waters from the three major oceans move to the Southern Ocean where the intensive vertical mixing occurs. After mixing in the Southern Ocean, the resultant homeogenous water (Montgomery, 1958; Carmack, 1977) becomes the major source of the Antarctic Bottom Water (AABW) which spreads back out into the deep world oceans (Wust, 1939; Lynn and Reid, 1968; Reid and Lynn, 1971).

The Weddell Sea is considered the major source of the AABW (Deacon, 1937; Reid and Lynn, 1971; Carmack and Foster, 1975). Because of the Weddell Sea's role in the formation of the world's ocean bottom waters, an understanding of the carbonate chemistry in the Weddell Sea is essential to an understanding of the global biogeochemical cycle of carbon (Gordon, 1971; Broecker, 1979; Weiss et al., 1979; Carmack, 1983). Unfortunately, very few high precision-carbonate sampling programs have been conducted in the Weddell Sea (Weiss et al., 1979). Because we do not know the characteristic properties of the water near its origin, interpreting variations of the carbonate chemistry and calculating excess CO₂ in the deep oceans are difficult (Chen, 1984). Furthermore, the scant data in the Weddell Sea were all collected in the summer, and whether the summer data are representative of the mainly winter-formed deep waters is uncertain (Chen and Pytkowicz, 1979; Chen, 1982a, b).

This package presents the carbonate data from the Weddell Sea that were obtained during the winter of 1981 as part of the US-USSR Weddell Polynya Expedition (WEPOLEX-81). These data represent the initial concentrations calcium and alkalinity in the most important source region of world ocean bottom waters at the time they were formed.