Reconstructions of lake-water salinity at decadal resolution for the last 2000 yr are compared among three lakes in North Dakota to infer regional patterns of drought. The intersite comparisons are used to distinguish local variation in climate or hydrology from regional patterns of change. At one lake, diatom-inferred salinity and lake-water Mg/Ca inferred from ostracode shell chemistry are coherent, both in terms of direction and magnitude of change, indicating that each is a robust technique for reconstructing lake-water chemistry. The data show that the last 2000 yr have been characterized by frequent shifts between high and low salinity, suggesting shifts between dry and moist periods. Long intervals of high salinity suggest periods of multiple decades when droughts were intense and frequent, thus indicating times when drought was more persistent than in the 20th century. Both the Medieval Period and Little Ice Age were hydrologically complex, and there is no clear evidence to suggest that either interval was coherent or unusual in effective moisture relative to long-term patterns. Differences among the three sites may be attributed to variation in local hydrology, and these differences emphasize the need for multiple sites in deriving regional climate interpretations from paleoecological data. (C) 2000 University of Washington.
Bibliographical noteFunding Information:
Eric Grimm obtained the cores and provided some of the AMS radiocarbon dates. P. Mueller, B. Haskell, J. Xia, R. McEwan, and R. Knurr assisted with core sampling and laboratory analyses. We thank B. Cumming for statistical advice and E. Grimm, J. Almendinger, J. Donovan, and A. Smith for helpful discussions on regional paleohydrology. This research was funded by the NSF (ATM 94-14381 and ATM 96-32040) and NOAA (NA36GPO302) and is a contribution by PRAIRIE (Paleoecological Reconstructions of Aridity: Interdisciplinary Research Iniative).
- Northern Great Plains
- Saline lakes