| dc.description.abstract | A portions of San Juan Mountains are located in the alpine critical zone, which extends from the boundary layer between the atmosphere and the surface of Earth. In this zone, atmospheric and geomorphic processes drive all interactions. The focus of this research is on changes associated with the location of potential permafrost in the San Juan Mountains of Colorado. Study of potential permafrost can provide important information regarding the distribution and stability of permafrost under warming climatic conditions. Understanding patterns of temperature and aspect are vital steps in understanding the distribution of potential permafrost in alpine environments, its current stability, and such changes that might occur in the future. To study this question, three objectives were assessed. First, historical climate records, standard adiabatic rate, and ArcGIS methods were applied to analyze the impact of temperature on the climate change. Second, aerial photographs and field investigations were applied to classify the spatial extent of permafrost in a selected region of the San Juan Mountains. Digital Elevation Models (DEM) in ArcGIS were created to evaluate elevation, slope, and aspect relative to the elevations of permafrost. Finally, the traditional temperature models and tracing the toe of rock glaciers were applied and compared to approximate the potential spatial increase or decrease in permafrost.
Temperature observations from 1895 to 2013 in the study area indicate that mean annual temperatures (MAAT) have increased by ~2.7C. The temperature changes in this location are much greater in the winter than other seasons and these changes are unprecedently higher and faster changes when compare to global average. A frost-number study shows that one-third of the soil may be frozen in a year. Additionally, high frost numbers tend to occur in the higher elevations and along the northeastern part of study area. The temperature at top of permafrost (TTOP) analysis reveals that local variation in aspect accounts for most of the changes in the extent of potential permafrost. Permafrost distribution models and topoclimatic information from rock glaciers, however, show almost no difference in the extent of permafrost for the objective methods. Permafrost locations display a strong correlation with rock glaciers except in the northeastern part of the study area where no rock glaciers are found, but the potentail permafrost may still exist.
This study indicates that the San Juan Mountains have experienced climate change. Global temperature changes have influenced alpine permafrost in the San Juan Mountains. Higher summer and winter temperatures since 1980, along with more precipitation, can contribute to the decreasing extent of potential permafrost in this region. | en |
