Speaker: Bryan Black, Laboratory of Tree-Ring Research, University of Arizona

Topic:

Multicentennial perspectives on extreme climate and natural disasters in the Pacific Northwest

The dendrochronological technique of crossdating ensures that tree-ring chronologies are exactly placed in time, allowing them to be readily integrated across species, locations, and with observational environmental and climate records. In the Pacific Northwest and northeastern Pacific, these techniques are increasingly applied to the forests of western Cascadia as well as growth increments of long-lived fish and bivalve species in the California Current and Gulf of Alaska. These chronologies illustrate remarkable covariance across marine and terrestrial ecosystems while forming the foundation for multi-species, multi-proxy reconstructions of climate and natural disasters. Fish otolith and tree-ring chronologies in the California Current capture an unprecedented trend in rising volatility of winter hydroclimate and upwelling. Farther north, temperature-sensitive bivalve and tree-ring chronologies spanning multiple centuries benchmark unprecedented warming and associated shifts in the climate variables that limit growth. New western Cascadia tree-ring chronologies are also critical for dating trees killed in landslide- and fault-formed lakes. Tree death dates yield new insights into the spatial extent and landscape-level impacts of the 1700CE Cascadian Subduction Zone earthquake while revealing the extent and timing of crustal fault ruptures, including a late Holocene multi-fault earthquake underneath what is now Seattle, Tacoma, and Olympia, WA. Indeed, the infusion of dendrochronology with novel stable isotope and high-resolution radiocarbon techniques is poised to usher in the next generation of high-resolution paleoseismic reconstructions for the region.