Holocene hydroclimate and drought in Western North America: patterns and variability indicated by isotope proxies of paleoenvironmental water, Alaska and alpine Colorado.

Long-term perspectives of climate effects on water (i.e., hydroclimate), such as drought, for the North American Rocky Mountain region are available from paleoenvironmental archives. The hydroclimatic proxy explored here is the stable isotopic signature of paleoenvironmental water (oxygen and hydrogen) from a variety of materials; lake sediment carbonates, peatland plant and tree cellulose (fossil and living), and permafrost pore-waters. We can constrain paleoenvironmental interpretations with additional proxy data (e.g., pollen, macrofossils, carbon isotopes, sedimentology etc.) and studies of modern water isotopes (accumulated snowpack, precipitation and lakes).  North Pacific and western North American climate proxy records have long provided abundant evidence for late Quaternary hydroclimatic change, mainly in terms of effective moisture, or precipitation minus evaporation.  To investigate additional aspects of the hydrologic cycle, recent explorations have focused on changes in atmospheric circulation patterns, including those that effect the season of precipitation dominance and influence physical phase (snow, rain), and topographic effects. This talk will discuss recent research on these topics in Alaska and Colorado. In Alaska these dynamics have important implications for the cryosphere including carbon stored in permafrost and peatlands. In Colorado, where snowpack is the primary water source for the region, results are pertinent to water availability and planning.  Such long temporal perspectives, combined with increasingly detailed spatial coverage, are developed to more fully understand present mechanisms of hydroclimatic change, which can better inform expectations for corresponding impacts on landscapes and ecosystems going into the future.