Reconstruction of late-Pleistocene equilibrium-line altitudes and paleoenvironments: Uinta Mountains, Utah and Wyoming

Climatic and paleoenvironmental changes of the Uinta Mountains are estimated by comparing oxygen isotope stage six (155 ka BP to 130 ka BP) and oxygen isotope stage two (30 ka BP to 12 ka BP) age glacial equilibrium-line altitude (ELA) trend surfaces to present (i.e., 1972 to 1990) snow accumulation trend surfaces. Whereas the present ELA was estimated from snow accumulation and regional climate data, Pleistocene full-glacial ELAs were estimated from reconstructed glacial geomorphology. Present snow accumulation and regional climatic data are also evaluated to understand relationships between snow accumulation patterns and climate variability. The evaluations reveal that snow accumulation trend surfaces have super gradients during moist winters and slope in the general direction of the upper-level airflow. The present and Pleistocene ELA surfaces were compared to estimate temperature, precipitation, and airflow variations. These variations include: (1) a 9.6;The differences between the Pleistocene and present ELA surfaces indicate that major climatic variability has occurred. Temperature differences are in general agreement with estimates from other investigations in the region. Although Pleistocene precipitation is estimated to have been less than present, the moisture supply to the Uinta Mountains appears to have been influenced by paleolakes to the west in the Bonneville Basin. The Pleistocene air-flow is projected to have been more zonal than present. Where climate differences are shown to exist between the glacial episodes and present, temperature and precipitation differences between the stage six and the stage two glacial episodes are also thought to have occurred.