Collaborative Research: Late Holocene Climate Variability From Stable Isotope Ratio Analysis of Coast Redwood Tree Ring Cellulose

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This project aims to explore the relationship between atmospheric moisture and climate as recorded in trees. The researchers postulate that fog is a strongly integrative measure of interannual summer climate variability at the ocean-land-atmosphere interface of the U.S. Pacific Coast. They further suggest that there is strong coupling to coastal wind, sea-surface temperatures (SSTs), land temperatures, and the Pacific Decadal Oscillation (PDO). The broad aim of the research is to assess changes in the nature of high-frequency (El Nino Southern Oscillation-scale) and multi-decadal (PDO) variability in the isotope records and to provide new information on the character of the Little Ice Age and Medieval Climate Anomaly on the U.S. Pacific coast. The researchers argue that the climate of coastal northern California sets the stage for recovering a novel high-resolution paleoclimate record using stable isotopes from tree-rings. They propose to focus their attention on the Coast Redwood (Sequoia sempervirens [D. Don] Endl.), a long-lived tree species, with some individuals exceeding 2,000 years in age. The researchers hypothesize that stable isotope analysis of ancient redwood tree rings could provide annually-resolved proxy information on large-scale climate mechanisms over the last 1,000 years and they aim to place warm-season changes in long-term context so that the range of natural and anthropogenic variations can be assessed.This hypothesis is based on the team's previous research that established the feasibility of reconstructing climate, including northern California precipitation and fog in the spring and summer seasons, from the U.S. Pacific coast using stable isotope analysis of carbon and oxygen of redwood tree-ring cellulose. Their research also shows that over the past century, coastal northern California summer climate has changed substantially, including a ~33% reduction in fog frequency and a coastal SST increase of ~0.8°C. The broader impacts involve pursuing a high risk research plan that could yield a new perspective on reconstructing climate from environmental and ecological data. The research could be of value to a broad range of users that include climatologists and forest managers. The project includes a strong collaboration between a non-PhD degree granting institution and a high performing research laboratory.