Subalpine snowpack-climate manipulation and modeling experiment at Niwot Ridge, CO and Valles Caldera National Preserve, NM

Meromy, Leah

Graduate Thesis Or Dissertation

Subalpine snowpack-climate manipulation and modeling experiment at Niwot Ridge, CO and Valles Caldera National Preserve, NM Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/hx11xf59n

Abstract

At Niwot Ridge, CO, a global warming experiment using near-infrared (IR) heaters is being conducted. Investigation of snow accumulation, snowmelt, and soil microclimate found the heaters to influence these variables at the subalpine experimental site. These changes were compared to an environmentally similar yet naturally warmer subalpine snowpack in the Valles Caldera National Preserve, NM. Over the 2010 and 2011 snow seasons, snow accumulated 42% lower on average and melted out 1-37 days earlier in the warmer plots (CO heated and NM) compared to the CO controls. Soil temperature was 2.6 °C greater on average in warmer plots compared to controls. Peak soil moisture was 0-12% lower in warmer plots versus controls. In order to estimate differences in energy and mass balance exchange at the snow surface in control versus warmer plots, the one-dimensional, physically based snowmelt model, SNOWPACK, was used. Energy and mass fluxes in control cases were compared to heated, NM, and synthetically warmer cases. Model results found that the heaters alter radiative, turbulent and mass fluxes by amounts comparable to differences between CO and NM fluxes. The sign and magnitude of energy and mass exchanges were similar between the control and synthetic models. The proportion of the energy flux associated with latent heat was 11-30% of the total energy flux in heated and NM models compared to 2-9% in control and synthetic models during snowmelt, and subsequently the associated evaporative loss to the atmosphere was much lower in control cases relative to NM cases. These results indicate that warmer conditions (i.e. increased average air temperatures) as projected in the coming decades will change snow surface energy fluxes, timing and magnitude of snow accumulation and melt, and soil temperature and moisture. Results of this study aid in the interpretation of climate manipulation experiments and modeling as they pertain to snowpack, and contribute to a better understanding of the interactions between climate, hydrology, and ecological processes.

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