| A diatom-inferred paleosalinity record was reconstructed at 5-year intervals for the past 2000 years using a 74-lake training set for the Northern Great Plains. In addition to the recent fresh period, four fresh periods have occurred in the last 2000 years, peaking at 200, 500, 700 and 1000 A.D. Fluctuations between fresh and saline conditions have been consistently rapid and were likely accompanied by large lake level shifts. The period from 1070--1960 A.D. was saline, coinciding with a regional climate shift, as compared to 0--1070 A.D. During at least part of this prolonged saline period, Devils Lake may have had high water levels, which would have prevented rapid freshening. Lake level began to drop in the late 1800s, reaching a historical low in 1940. The recent increase in precipitation changed both lake level and salinity drastically, similar to the behavior of Devils Lake in the first millennium. |
