Hemiarid Basin Sensitivity to Abrupt Climate Change: The Trans- Pecos Closed Basin

David E. Wilkins (Department of Geography, University of Utah, Salt Lake City, UT 84112-9155; ph. 801-581-8218; email: david.wilkins@geog.utah.edu); Donald R. Currey (Limneotectonics Laboratory, Department of Geography, University of Utah, Salt Lake City, UT 84112-9155; ph. 801-581-6419; email: currey@geog.utah.edu)

The Trans-Pecos Closed Basin is the southeasternmost palaeolake basin in the US. Analysis of sedimentary records from Palaeolake King yield timing for four abrupt and rapid transgressions during the LGM, following low stands that were radiocarbon dated at 22.6 ka, 19.1 ka, 17.2 ka, and 15.5 ka. These transgressions correlate with high stands in the Estancia and San Augustin basins to the north and northwest. The timing and quasi-periodicity of these transgressive events suggest a teleconnection with northern hemisphere marine cooling events. Periodic intensifying of the Laurentian anticyclone appear to have resulted in the southward displacement of the LGM subpolar jet stream and associated storm tracks; this displacement produced an environment of increased effective moisture, resulting in the formation of lakes in these closed-basins.

A basin's location with respect to the mean position of LGM winter storm tracks was an important factor in determining its sensitivity to changes in effective moisture. In basins located along the extreme southern edge of LGM storm track displacement, lakes would have formed only in response to only the most extreme climate changes; this is reflected by low Mifflin Index (MI) values for palaeolakes that formed along the subtropics (Lake King MI = 0.04). Fluctuations in lake surface elevations resulting from changes in a basin's hydroclimate equilibrium line altitude serve as a proxy measure of temporal and spatial variability of effective moisture within that basin. The Trans-Pecos closed basin is presented as an example of the hemiarid basin as a sensitive indicator of climate change.