Changes in atmospheric circulation, precipitation patterns, and lake hydrology over the last ~12,000 years in Alaska

Category: Time:
Wednesday, February 2, 2022 - 12:00 to 13:00
Room: URL: Speaker:
Ellie Broadman
Laboratory of Tree-Ring Research, University of Arizona
Margaret Evans & Dave Meko
Calendar Status:

As a result of rapidly rising temperature in Alaska, glaciers are melting, sea ice is diminishing, lake levels are dropping, and precipitation patterns are changing. These rapid changes are superimposed upon naturally occurring patterns of climate variability in the North Pacific and Arctic Ocean basins, and must be interpreted in the context of these longer-term changes. However, due to the challenges of inferring past climate conditions from natural archives (e.g., lake sediments), uncertainties remain in our understanding of these naturally occurring sources of climate variability. In this talk I will present new reconstructions of changes in atmospheric circulation, precipitation patterns, and lake hydrology over the last ~12,000 years in southern and Arctic Alaska. These multi-proxy, lake-sediment-based reconstructions feature diatom oxygen isotopes, and are interpreted alongside climate model simulations and mass balance modeling experiments. Results support existing evidence for a shift in North Pacific hydroclimate ~4,000 years ago, and demonstrate that this shift was connected to changes in the extent of Arctic sea ice, and to precipitation patterns in Arctic Alaska. The results also reveal that these synoptic and regional drivers of hydroclimate can be difficult to identify in paleo oxygen isotope datasets, due to site-specific climate and environmental variables that influence the oxygen isotope composition of lake water. Multi-proxy and multi-method approaches prove useful for disentangling these hydroclimatic variables in the paleo datasets.