Hydrologic Variation in the Northern Great Plains During the Last Two Millennia

Abstract

Reconstructions of lake-water salinity at decadal resolution for the last 2,000 years 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 2,000 years 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.

Fire cycles in North American interior grasslands and their relation to prairie drought

“…), as well as during decadal droughts of the 19th to 20th centuries, such as the Dust Bowl (19)(20)(21)37). Although hydrologically variable, two distinct periods of drought have been identified during the MWP, whereas prolonged dry conditions have been suggested for the LIA (19)(20)(21). At Kettle Lake, high sedimentation rates are accompanied by several oscillations in carbonate mineral content, grass pollen, and charcoal flux during the MWP (Fig.…”

“…An annual deficit of precipitation minus evaporation also characterizes the region (15), making it highly sensitive to changes in the moisture regime. Previous paleoclimatic investigations have documented oscillations in several disparate climate proxies, revealing a high degree of past climatic variability on the plains (13,(16)(17)(18)(19)(20)(21)(22), especially in precipitation. Such variability has been linked to solar cycles (21) and to Pacific Decadal and Atlantic Multidecadal Oscillations (23,24).…”

Holocene Stratigraphy and Geomorphology of Flintstone Hill, Lauder Sandhills, Glacial Lake Hind Basin, Southwestern Manitoba

“…In general, these climate-landscape response models indicate greatest landscape stability occurs during climatic episodes characterized by moist, cool, relatively drought-free conditions when water tables are high and vegetation cover is abundant. Conversely, greatest eolian activity occurs during warmer/drier (higher growing season potential evapotranspiration and lower water tables, e.g., Laird et al, 1996a, b;Fritz et al, 2000;Hopkins and Running, 2000), and more drought-prone climatic episodes when highmagnitude, low-frequency droughts and storms are more common and more severe (Katz and Brown, 1992). In addition, for climatic conditions near the intrinsic instability/stability threshold for dunes, minor changes in drought frequency and magnitude may reactivate or stabilize dunes (Rosensweig and Reibseme, 1990;Muhs and Maat, 1993;Wolfe et al, 1994;Lemmen et al, ed., 1998;Lemmen and Vance, 1999;Hopkins and Running, 2000).…”

Evaluating climatic and non-climatic influences on ion chemistry in natural and man-made lakes of Nebraska, USA

“…In such areas, multiple sites, coupled with a clear delineation of the hydrologic setting of each basin, may be necessary to clearly reconstruct the likely causes of salinity variation through time and its climatic drivers (e.g. Fritz et al, 2000;Telford & Lamb, 1999).…”