DUNEFIELD RESPONSE TO CLIMATE CHANGE ON THE NORTH AMERICAN GREAT PLAINS

Chronological studies from dunefields across the North American Great Plains document a history of alternating periods of dune activity and stability throughout the late Pleistocene and Holocene. Periods of stability are inferred from paleosols in aeolian stratigraphy and indicate increased moisture availability and stabilization from vegetation. Periods of activity are inferred from the absence of soil development within aeolian stratigraphy and correspond mainly to periods of prolonged moisture deficit when vegetation cover was limited. These features represent end-members of a continuum of states between active mobile dunes on one end and inactive stabilized dunes on the other. To date, the transition periods between these states have received little consideration. Furthermore, the resistance of dune systems to displacement from climate change and their ability to recover afterward is relatively unknown. To address these issues, we incorporated theoretical and conceptual models and ideas from the literature as well as empirical data from previous studies in order to develop a model of the response of dune systems to climate change on the Great Plains. The model is a working hypothesis and proposes a non-linear response of dune activity to climate change under the assumption that vegetation cover is the main limiting factor on dune activity. Simulations show that small perturbations during the stabilization of dune systems can prolong dune activity for much longer intervals than when steady state conditions are assumed. The model provides some evidence to support the idea that many areas with active dunes on the northern Great Plains may still be recovering from perturbations in the late 1700s. The model also compels a more critical view of the association between dune activity and climatic variations. In some cases, for instance, the synchronicity between records of dune activity and other proxy records of climate change may not be apparent because of the possibility of lags and nonlinear response. Despite the geographic focus of this study, the model appears applicable to a variety of environments where dune activity is limited, in part, by vegetation cover.