Cold-Air Pools and Regional Warming in the Lake Tahoe Region, Central Sierra Nevada of California—Observations and Considerations regarding the Future of Climate-Change Refugia

Abstract:

Naturally occurring climate refugia, specifically in the form of cold-air pools (CAPs) in mountain basins, are increasingly discussed as potential safe havens against some impacts of global warming on western ecosystems and cold-adapted species. A key concern in these discussions should be: How will CAPs react to regional warming? Several broad possibilities exist: CAPs may “resist” regional warming, remaining as cool as ever despite warming of their surroundings. CAPs may “reflect” regional warming, experiencing temperature increases that are roughly equal to the warming of their surroundings but that leave the CAP as cool relative to their surroundings as ever. Or CAPs might “disintegrate” in the face of regional warming, losing their special cool status relative to surroundings and in the process warming much more than their surroundings. An evaluation of historical observations of wintertime cold-air pooling in the Lake Tahoe basin and adjacent Truckee drainage offers examples of CAPs that have resisted regional warming (Tahoe) and that have reflected regional warming (Truckee). These two CAP responses to warming suggest that no single fate awaits all CAPs in the Sierra Nevada. Rather, different CAPs will likely evolve in different ways, depending on their topographic configurations (e.g., closed vs draining basins), topographic depths, CAP areas, and even (in the case of the Tahoe basin) thermal conditions at the base of the CAP. These CAP examples also suggest a need for research on the possibility of equivalent future responses by other, non-CAP climate refugia in a warming world.