Document type: DU ETD
Collection: Geology Theses  
Title Snowcover Controls on Alpine Soil Surface Temperature Patterns, Niwot Ridge, Colorado, U.S.A.
Author(s) Hamann, Hillary Beth
School/Department Department of Geography
Institution University of Denver
Degree Type Master's
Degree Name M.A.
Type of Resource text
Degree Date 1998
Digital Origin reformatted digital
Rights Statement All Rights Reserved
Reason for Restrictions No restrictions
Type of Restriction No restrictions
Keyword(s) Geography
Genre Dissertations, Academic
Abstract Seasonally frozen soils play an important role in many hydrologic, biologic, and hydrochemical processes. In the alpine, heterogeneous vegetation, topography and snow conditions during the winter should affect spatial and temporal variations in soil temperatures. In 1996-97 a network of soil temperature recorders were installed at 3500 m on Niwot Ridge to evaluate variations in surface soil temperatures and the primary controls on spatial and temporal variability of ground surface conditions. This study utilized a constructed snowfence on the Ridge as well as naturally occurring shallow, moderate and deep snow deposition sites. Snow depth was monitored throughout the winter season, and a reconnaissance of ground surface conditions was carried out prior-to and after snowmelt to look for basal ice at the snow-soil interface. Available data was utilized to examine soil moisture, vegetation and snow cover as primary controls on temperatures and temperature variations in the soil. Results indicate that although interactions occur between vegetation, soil moisture and soil temperatures, snow cover maximum depth and timing information can be used as a simple and effective predictor of general soil surface temperatures and variations. Maximum snow accumulations at the study site ranged from 10 cm to 560 cm and occurred in late April, 1997. Results from the 1996-97 snow year show that as seasonal snow cover depth and duration increase, short term temperatures variations are delayed and dampened. Sites with early snow accumulation less than 40 cm showed the greatest and fastest response to synoptic temperature changes. At sites where the early season snowpack ranged from 40 to 90 cm, response to general synoptic temperature trends was evident, though temperatures and their range were dampened by up to 10° C. The depth and timing of the snow cover also influenced minimum temperatures, the timing of minimum temperatures and the duration of an isothermal period at the end of the snow season. Snow cover and soil temperatures also appeared to affect the occurrence of basal ice and snowmelt flowpaths. Results of the basal ice survey point to antecedent soil moisture in the fall and spring meltwater supply as primary conditions necessary for basal ice formation on Niwot Ridge.
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