Could increased summer rains save mountain ecosystems as snow disappears?
Abstract
As temperatures warm, more winter precipitation will fall as rain rather than snow, leading to higher-elevation snowlines, increased surface temperatures, and decreased surface albedo. Collectively, these feedbacks lead to enhanced upslope flows (Letcher and Minder 2017, https://doi.org/10.1175/JAS-D-16-0158.1), which lead to increased convective summer precipitation in the mountains (Rasmussen et al. 2017, https://doi.org/10.1007/s00382-017-4000-7). We hypothesize that these effects will be greatest in areas with less forest cover (greater albedo feedbacks) and in areas with a summer moisture source (e.g., a connection to monsoon-related flow). Areas with these characteristics may retain tree species into warmer, winter-drier climates that would not otherwise be able to survive, as was observed in the eastern Sierra Nevada during the Medieval warm period (Millar et al. 2006, https://doi.org/10.1016/j.yqres.2006.05.001 ). In contrast, other forested areas in the Western U.S. have experienced drier summers corresponding to increased fire activity in recent years (Holden et al. 2018, https://doi.org/10.1073/pnas.1802316115). Differing summer weather and fire patterns on the western (more forest cover, less access to monsoon moisture) and eastern (less forest cover, more access to monsoon moisture) sides of the Sierra Nevada in recent high and low snow years illustrate these concepts. Surface observations may not be sufficient to detect convective mountain precipitation, and so we advocate for further analysis of satellite and streamflow observations, combined with high-resolution modeling, to fully understand these patterns and their implications.
We thank Catherine Raphael at NOAA GFDL for graphics support.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGC44B..04L
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSES;
- 1621 Cryospheric change;
- GLOBAL CHANGE;
- 1630 Impacts of global change;
- GLOBAL CHANGE;
- 1637 Regional climate change;
- GLOBAL CHANGE