Snow loss on the San Francisco peaks: Effects of an elevation gradient on evapo-sublimation

Samples were collected over an elevation gradient to isolate the effects of elevation on evapo-sublimation (E-S) in the San Francisco Peaks of northern Arizona. Gravimetric and isotopic fractionation measurements were taken to evaluate the cumulative effect of evaporative and sublimative processes on surficial snowpack layers.;Measurements were made at three elevations spanning 490 m. Each elevation consisted of an open and a canopied site. Open sites were characterized as having greater than 65% open sky, canopy sites as having less than 30% open sky. The distance between open and canopy sites was at most 21 m.;Graphical results demonstrate a decrease in E-S with elevation, with the exception of the middle elevation (site M), which had the lowest E-S values in the study for both open and canopy sites. I postulate that these uniformly low values are the result of considerably higher surrounding forest density at site M. This decreased wind fetch and speed, decreasing the amount of moisture scoured from the surface, yielding lower E-S rates.;Canopy sites were found to have greater E-S rates than open sites at all three elevations, likely due to nocturnal infrared radiation emitted by canopy cover. E-S rates at canopy sites were found to be on average 23% higher than the open site of the same elevation.;Statistical results failed to demonstrate a significant relation between elevation and E-S. Sample size was not large enough to resolve the high variability observed in measurements of E-S. The low and middle sites exhibited a significant difference between open and canopy sites, however the highest elevation did not, likely due to the influence of frequent high winds.;The relation between isotopic fractionation and E-S was found to be insignificant. This was attributed to an insufficient spatial distribution of snow samples collected at each site. A greater number of snow samples may be necessary to capture the high spatial variability of E-S as a micro-scale process.