CONCEPTUALIZING THE SHIFTING ROLES OF PRECIPITATION AND EVAPORATION IN BERINGIA ACROSS THE PLEISTOCENE-HOLOCENE TRANSITION USING A WATER ISOTOPE APPROACH

The fundamental importance of moisture on Beringian landscapes is established, and yet threshold ecosystem responses to changes in precipitation (P) and evaporation (E) remain unexplored. A prominent example is a rise in P - E (moisture balance) from the full glacial into the Bølling Allerød, when lake levels rose, and shrub birch expanded regionally. However, it remains unknown how these prominent hydrologic and ecologic changes were driven by changes in P and E, respectively. Similar questions exist for the Younger Dryas and early Holocene. A better understanding of precipitation amount and seasonality, and subsequent factors contributing to water cycling such as evapotranspiration and evaporation (as influenced by temperature, humidity, radiation, wind) and infiltration/flow/permafrost are needed to understand impacts of climate change on arctic regions. Water isotope ratios are widely used to study the hydrologic cycle: oxygen and hydrogen isotope values from lake, river, frozen ground, and meteoric water contain information about many variables of importance to precipitation and evaporation fluxes. Guided in addition by proxy data, including vegetation change and lake-levels, and by isotope-enabled climate models, we present a conceptual framework to extract complex P and E information across the deglacial transition in eastern Beringia. The approach provides specific hypotheses to be tested by paleoclimatic reconstructions based on lake water isotope ratios using lake sediments.