The Effects of a Climate Manipulation Experiment on Snow Properties, Snow Surface Energy Balance, and Soil Temperature and Moisture Along an Elevational Gradient on Niwot Ridge, Colorado

摘要

This research investigated the influence of near-infrared heaters used in climate manipulation experiments on snow properties (e.g. snow depth, grain size, grain shape, density, temperature), snow surface energy balance, and soil temperature and moisture at three sites along an elevational gradient on Niwot Ridge, CO. At the lower subalpine site (LSA), heated plots experienced an ephemeral snow cover, never reaching more than 45 cm of snow. Snow depths between heated and control plots at the upper subalpine (USA) and alpine (ALP) were similar but snow disappearance occurred 0 to 18 days earlier in heated plots relative to controls. Heated plots in all three sites experienced warmer soil temperatures and higher soil moisture during the winter relative to control plots. Overall, the effect of the heaters on snow properties, soil temperature, and soil moisture decreased with increasing elevation. Heaters altered the snow surface energy balance by increasing incoming longwave radiation (LWin). In order to derive estimates of energy and mass balance exchange at the snow surface in heated and control plots, the one-dimensional, physically based snowmelt model SNOWPACK was used. In heated plots at the LSA, net radiation accounted for 80 to 100 % of the energy available to melt snow compared to 35% in control plots. In heated plots at the USA/ALP, net radiation accounted for 100% of the energy available for melt when snow depth exceeded heater height. However, when snow depth is below the heaters (1.2 m), only 5% of the energy for snowmelt comes from net radiation. Model results illustrate greater mass losses to sublimation/evaporation (54 to 83% of total SWE) in heated plots compared to control plots (6 to 38% of total SWE). The results of this study will aid in the interpretation of warming experiments, as well as develop a better understanding of the interactions between climate, hydrology, and ecological processes.