Journal cover Journal topic
Climate of the Past An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/cp-2017-107
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
29 Sep 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Climate of the Past (CP).
Drought and vegetation change in the central Rocky Mountains: Potential climatic mechanisms associated with the mega drought at 4200 cal yr BP
Vachel A. Carter1,2 and Jacqueline Shinker3 1RED Lab, Department of Geography, University of Utah, Salt Lake City, 84112, USA
2Department of Botany, Charles University, Prague, 128 01, CZ
3Department of Geography and Roy J. Shlemon Center for Quaternary Studies, University of Wyoming, Laramie, WY 82071 USA
Abstract. Droughts are a naturally re-occurring phenomena that result in economic and societal losses. Yet, the most historic droughts that occurred in the 1930s and 1950s in the Great Plains and western United States were both shorter in duration, and less severe than mega droughts that have plagued the region in the past. Roughly 4200 years ago, a ~ 150-year long mega drought occurred in the central Rocky Mountains, as indicated by pollen evidence from lake sediments from Long Lake, south-eastern Wyoming. However, pollen evidence does not record the climate mechanisms that caused the drought; they only provide evidence that the drought occurred. A modern climate analogue technique using North American Regional Reanalysis data was applied to the sedimentary data in order to identify possible synoptic and dynamic patterns that may have caused the mega drought at 4200  yr BP. Our results demonstrate the warm and dry conditions were a result of anomalously higher-than-normal geopotential heights that were centred over the Great Plains beginning in spring and persisting until the fall. Drought conditions during the growing seasons was the result of the anomalous high-pressure ridge, which suppressed moisture transport via the low level jet from the Gulf of Mexico, as well as brought in dry continental air from in the interior region of North America. Conditions associated with the mega drought likely led to the changes in vegetation composition as evidenced by the pollen record.

Citation: Carter, V. A. and Shinker, J.: Drought and vegetation change in the central Rocky Mountains: Potential climatic mechanisms associated with the mega drought at 4200 cal yr BP, Clim. Past Discuss., https://doi.org/10.5194/cp-2017-107, in review, 2017.
Vachel A. Carter and Jacqueline Shinker
Vachel A. Carter and Jacqueline Shinker
Vachel A. Carter and Jacqueline Shinker

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