This award supports a team of researchers who seek to identify site characteristics and tree species in an effort to investigate analytical methods that capture a winter temperature signal from delta18-oxygen isotopic variations in tree-ring cellulose from two sites in central Colorado and Montana Rockies. The science goal is to assess the potential for reconstructing cool-season temperatures for the Rocky Mountain region. The researchers will also evaluate the usefulness of delta18-oxygen isotope chronologies for reconstructing atmospheric circulation patterns that influence temperature variability across North America, such as the Northern Annular Mode and the Pacific North American Pattern. The broader impacts involve working with Colorado and Montana land- and water-resource managers to use information from past climate and hydrology to inform future planning. The project would support a new postdoctoral scholar with plans for K-12 lessons based on the project.