W.B. Lyons, K.A. Welch, University of Alabama
P. Sharma, Purdue University, PRIME Lab
Geochimica et Cosmochimica Acta 62 (1998) 185-191
We have analyzed water samples from lakes Bonney, Fryxell, and Hoare in the McMurdo Dry Valleys (MDV) area of southern Victoria Land, Antarctica. These data, coupled with those of earlier work, provide a new view of the sources of chloride ion to these lake systems. Although these lakes lie within the same geologic domain and climatic regime, their chemistries are very different in that the hypolimnions have varying salinities and major ion ratios. The bottom waters of both lobes of Lake Bonney have low 36 Cl:Cl ratios (<6 x 10 -15 ) derived from a probable mixture of seawater (0 x 10 -15 ) and a nearby saline seep (9-10 x 10 -15 ). On the other hand, the 36 Cl:Cl ratio of both the bottom water and the surface water of Lake Hoare, the least saline of the lakes, is similar to ratios found in chlorine salts in the local soil and meteoric sources by the earlier work (210 vs 440 x 10 -15 ) of Carlson et al. (1990). The water from Lake Fryxell has an intermemdiate ratio, perhaps indicating a mixture of both meteoric input and "older" chloride. Our recent surface-water measurements from the three lakes demonstrate a very significant decrease in the 36 Cl:Cl ratio from meltwater that entered the lakes in 1984-1985. These data provide evidence of the dynamic geochemical/hydrological behavior of these lakes, abd coupled with the earlier data, help to better define the importance of differing sources of solutes to the lakes.