Amanda Flory | 2025 I.S. Symposium

Name: Amanda Flory
Title: Volcanic Signatures in Yellow-Cedar: Understanding Mechanisms of the Pacific Decadal Oscillation
Majors: Environmental Studies; Environmental Geoscience
Advisor: Greg Wiles; Matt Mariola

This study uses yellow cedar (Cupressus nootkatensis) tree ring width data from Southeast Alaska to provide additional evidence of volcanic cooling following the estimated 1458, 1600, 1695, and 1808 eruption events. Dude Mountain, located in Ketchikan, Alaska, was chosen as the study site for its high-elevation (863m) and minimized stand disturbance. This well replicated (1350-2023) ring-width record serves as a proxy for past temperatures and shows negative correlations with May, June, and July Sitka temperatures during the 1920s through the 1940s, but not with the PDO. This possibly suggests that the series does not respond to shifts in the PDO, but instead to shifts in the North Pacific current, which tend to be at their strongest during May and June. Stratospheric volcanic events can induce extended cooling to the North Pacific Current, delivering colder waters, winds, and temperatures into the Gulf of Alaska. These temperature fluctuations represent a key component of the PDO as it manifests in our study region due to the unique geospatial setting of Dude Mountain. We propose that our proxy may better reflect the North Pacific Current through North Pacific Ocean heat content, which could serve as a recorder of more consistent ocean temperatures associated with PDO phases.

Posted in Symposium 2025 on May 1, 2025.