Earlier and Slower Snowmelt in a Warmer World: Surprising Feedbacks to a Changing Climate
Abstract
Mountain snowmelt is a critical water source for downstream human populations and local terrestrial and aquatic ecosystems. Understanding how climate change will impact these systems hinges on the quantity of snowmelt and the timing of water availability. Here we demonstrate three relatively unknown trends in Western U.S. snowpack dynamics: 1) increasing magnitude of winter season ablation and 2) earlier initiation of snowmelt, and 3) slower snowmelt rates. We combined 463 Snow Telemetry (SNOTEL) stations with the UofI METDATA product to investigate the climatic drivers of snowpack trends from 1980-2015. A total 139 sites (30%) had significant increases in winter ablation (i.e. melt or sublimation prior to peak snowpack) averaging 1.1 cm of water per decade. Strikingly, rates of winter ablation were more strongly explained by absolute humidity rather than temperature, suggesting that latent heat gains were the dominant driver of increased winter ablation; consistent with the largest increases in the Pacific Northwest. Spring snowmelt shifted earlier by an average of 1.8 days/decade, with significantly earlier snowmelt initiation at 8% (36) of sites. In contrast to earlier initiation, the average spring snowmelt rate decreased by an average of 7.3 mm/day per decade, with significant decreases at 12% (55) of sites. Additionally, the top decile ablation rates slowed by 21.3 mm/day per decade on average, with significant trends at 32% (149) of sites. Presumably, the earlier initiation of snowmelt due to warming temperatures and increased humidity was partially offset by reduced solar radiation earlier in the year during lower sun angles. Our findings highlight that regional disparities in the role of sensible heat, latent energy, and net radiation in the snowpack energy budget can lead to differential sensitivity to climate change. Interactions between changing snowmelt timing, amount, and melt rates will have complex impacts on hydrologic partitioning that are poorly quantified.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.C13F..08H
- Keywords:
-
- 0736 Snow;
- CRYOSPHEREDE: 0740 Snowmelt;
- CRYOSPHEREDE: 0742 Avalanches;
- CRYOSPHEREDE: 1863 Snow and ice;
- HYDROLOGY