On the Identification and Characterization of Drought and Aridity in Postglacial Paleoenvironmental Records from the Northern Great Plains

Abstract

The Northern Great Plains region is especially sensitive to drought and is likely to be even more drought-prone under projected global warming. Drought has been invoked as an explanatory factor for changes seen in postglacial paleoenvironmental records. These proxy records may extend drought history derived from instrumental data. Moreover, in the last decade, some paleoenvironmental studies have been expressly undertaken for the examination of long-term drought history. Nevertheless, few such studies explicitly define drought. This makes it difficult to compare results or to understand what the results mean in terms of the operational drought definitions that are used in resource management. Operational drought is defined as usually short-term; longer sustained dry intervals reflect a shift to aridity. Therefore, high resolution paleoenvironmental proxies (annual or subdecadal) are best for the investigation of drought history. Such proxies include tree rings and some lake records. However, most lake-based records are sampled at lower resolution (decadal or subcentury) and are therefore providing aridity signals.Les Grandes Plaines du Nord sont particulièrement sensibles à la sécheresse et seront vraisemblablement grandement touchées par le réchauffement climatique prévu. La sécheresse est un facteur qui peut expliquer les changements observés dans les relevés paléoenvironmentaux postglaciaires. Ces derniers permettent de comprendre, sur une plus longue période, l’évolution de la sécheresse révélée par les données climatiques modernes. Au cours de la dernière décennie, plusieurs études paléoenvironnementales ont été expressément entreprises dans ce but. Toutefois, peu d’entre elles présentent une définition précise de la sécheresse. Cela complique la comparaison et l’interprétation des résultats en ce qui a trait à la définition de la sécheresse en phase active. La sécheresse active n’est habituellement que de courte durée ; les épisodes secs plus longs reflètent un passage à l’aridité. Les indicateurs paléoenvironnementaux de haute résolution (annuels ou de moins d’une décennie) sont les meilleurs pour suivre l’évolution de la sécheresse. Ces indicateurs comprennent les cernes de croissance des arbres et certaines données lacustres. Cependant, les données lacustres d’une résolution inférieure (à l’échelle de la décennie ou de la fraction de siècle) tendent à donner des signaux d’aridité.La región de las grandes praderas de Norteamérica es particularmente sensible a la sequía y será sin duda afectada por el calentamiento global por venir. Se ha propuesto que la sequía puede ser el factor que explique los cambios observados en el registro de paleoambientes postglaciares. Dicho registro permite comprender la evolución de la sequía obtenida a partir de datos cuantitativos modernos, durante un periodo mas largo de tiempo. Mas aun, en la ultima década algunos estudios paleoambientales se han llevado a cabo expresamente para examinar la evolución de la sequía a largo plazo. Sin embargo, pocos son los estudios que defi...

Biogeomorphic model of dunefield activation and stabilization on the northern Great Plains

“…If the period lasts for more than a decade, the perturbation is referred to as increased aridity (cf. Beaudoin, 2002). Although other perturbations can activate dunes (e.g., overgrazing, fire), paleoenvironmental evidence indicates that decade-to-century-scale aridity during the Holocene (b 10 ka) was the main trigger responsible for activating dunefields across the North American Great Plains (Muhs, 1985;Muhs and Maat, 1993;Forman et al, 1995Forman et al, , 2001Madole, 1995;Muhs and Holliday, 1995;Dean et al, 1996;Dean, 1997;Muhs et al, 1997a,b;Muhs and Wolfe, 1999;Wolfe et al, 2000Wolfe et al, , 2001.…”

Isotopic paleoecology of Clovis mammoths from Arizona

“…Stable isotopes in mammalian enamel have great potential as "paleo-drought" proxies, because they allow the reconstruction of seasonal changes in precipitation and vegetation patterns at a much finer temporal resolution than is obtainable using "traditional" proxies such as lake sediment cores (43). The study of stable isotopes in tooth enamel also shows great promise for understanding animal life histories, which is a key step in understanding late Pleistocene extinctions (7).…”

“…We define drought as a short-term (several years or less) decrease in rainfall amount, particularly during the growing season, in relation to the prevailing conditions at the time (43). In the SPV, there is stratigraphic evidence for a significant drop in the water table during the Clovis occupation (39).…”

Falling Lake Victoria water levels: Is climate a contributing factor?

“…In general, Manneh (1997) points out that a 1% change in rainfall results in a 3% change in runoff which in-turn reduces the Lake's recharge. While lake level fluctuations have been shown to track drought episodes (e.g., Beaudoin 2002), the concern here is the continual falling of the Lake Victoria levels, hence the authors acknowledge the need to investigate the contribution of climate change besides other environmental and man-made factors. Mistry and Conway (2003) investigated the climatological factors responsible for the rise in the lake level, and found out that there was a significant correlation between the Lake rainfall series and the Lake levels.…”