Abstract

We use light detection and ranging (LIDAR) imagery and optical stimulation luminescence dating to show that stable parabolic dunes on the Canadian prairies originated from active barchan dunes ~200 years ago. Residual dune ridges, marking former lower stoss slope positions of migrating dunes, record the transformation of barchan dunes to parabolic dunes between A.D. 1810 and 1880. Parabolic dunes stabilized by ca. A.D. 1910, with a few larger dunes and blowouts still active today. A dry, cool climate permitted sand transport to out-compete vegetation stabilization and, with lowered water tables, maintain desert-like barchan dunes with bare interdune sand sheets. These findings explain why dune fields of the southern Canadian prairies are currently more active than those of the United States Great Plains and the observation that dunes have stabilized under twentieth century warming. Our results emphasize the importance of viewing dune field responses to short-term disturbances in the context of longer-term system response, particularly when relatively modest climatic changes can cause major shifts in dune activity.

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