salinity waters from the Pacific. Despite the low salinity of the source, there is evidence that high-density waters can be produced in winter, especially where ice drift helps to maintain open water and thus prolong winter cooling and intensify production of near-freezing brines.
In summer there is a large amount of biological activity on the Chukchi shelf. Biological debris accumulates on the shelf bottom and decays. Shelf bottom water oxygen saturations under 25% and silicate concentrations to 1O0 μmol 1-1 were observed during AOS94. The combination of dense winter waters with high nutrient and low oxygen concentrations provides a source for the halocline oxygen minimum and nutrient maxima found throughout much of the Canadian Basin. The density of these waters is less than that of DSOW, but Swift et al. (1998) show that the Canadian Basin deep waters are also enriched in silicate derived from the Chukchi shelf, not by enrichment from in situ bottom dissolution. Results from the 1997 section across the Beaufort Sea slope into the deep Canada Basin substantiate this view. Silicate distributions along the Canadian basin boundary current (Figure 5) provide additional evidence that the Chukchi shelf produces dense waters which mix with the Atlantic layer, and at least occasionally penetrate to the abyssaol waters.
More obvious evidence of a dense shelf water contribution is found in the Makarov Basin. Anomalously cold, fresh water was found in a broad layer near 10O0 meters at one AOS94 station (Swift et al., 1998). This was the coldest, freshest water at this density yet observed in CTD profiles from the Arctic basins. Low nutrient, high oxygen, and high anthropogenic tracer concentrations marked this as water from a shelf source, probably from the Kara or Laptev seas, that has entered the Makarov Basin. Close examination of the CTD profiles revealed signatures of what were likely other, further decayed cold/fresh boluses in the Makarov Basin. Together with the Chukchi shelf waters these help to provide the low salinities in the DSOW density range in the Canadian Basin.
3. CONCLUDING REMARKS
Aagaard et al. (1985) show that there is a large volume of Arctic Ocean waters in the DSOW density range, presenting a large thermodynamic inertia that contributions of dense shelf waters must work against. The water column of the Barents Sea requires the least amount of net buoyancy change to produce dense water, making that region highly-favored to modify the properties of the Arctic Ocean interior waters in the DSOW density range.
REFERENCES
Aagaard, K., J.H. Swift, and E.C. Carmack, 1985: Thermohaline circulation in the Arctic mediterranean seas, J. Geophys. Res., 90, 4833-4846.
Anderson, L.G., E.P. Jones, K.P. Koltermann, P. Schlosser, J.H. Swift and D.W.R. Wallace, 1989: The first oceanographic section across the Nansen Basin in the Arclic Ocean. Deep-Sea Res., 36, 475-482.
Swif1, J.H., T. Takahashi, and H.D. Livingston, 1983: The Contribution of the Greenland and Barents Seas to the Deep Water of the Arctic Ocean. J. Geophys, Res., 88(C10), 5981-5986.
Swift, J.H., E.P. Jones, K. Aagaard, E.C. Carmack, M. Hingston, R,W. Macdonald, F.A. McLaughiln, and R.G. Perkin, 1998; Waters of the Makarov and Canada Basins. In press: Deep-Sea Res.
