Collaborative Research: P2C2--Multi-proxy Reconstructions of North Pacific Decadal Variability from Bivalve Mollusks and Trees

University Of Arizona, Tucson AZ

Investigators

Abstract

This project has three main scientific goals aimed at: 1) benchmarking pre-industrial ranges of North Pacific decadal variability for comparison to observed 20th century patterns as well as modeled paleo and future datasets of hemispheric climate; 2) addressing unresolved questions regarding poor agreement among existing tree-ring reconstructions of North Pacific decadal variability and the possibility that linkages across marine and terrestrial systems vary in character and strength over time; and 3) examining long-term linkages between the North Pacific and tropical Pacific by comparing reconstructions of North Pacific decadal variability to independent reconstructions of the El Nino Southern Oscillation. Decadal-scale variability in the North Pacific Ocean plays a fundamental role in the socioeconomic and environmental dynamics of western North America with clearly established implications for fisheries production, forest growth, wildfire, drought, and snowpack. This major mode of Earth's climate system has historically been characterized as the Pacific Decadal Oscillation for which signatures have been identified in biological and physical indicators across Asia, Australia, and South America and even in global-scale trends in sea level and surface temperature. However, there remains considerable and long-standing uncertainly in its behavior prior to AD 1900 and the extent to which 20th century dynamics are atypical in a multi-centennial context. In this study, three paleoclimate proxy data sources will be integrated to reconstruct North Pacific decadal variability. First, a network of exactly dated chronologies will be produced from growth-increment widths of long-lived marine bivalve Pacific geoduck (Panopea generosa), the growth of which is demonstrated to be highly sensitive to sea surface temperatures. Radiocarbon (14C) data in geoducks, once cross-dated and placed in the appropriate calendar years, will yield another perspective on North Pacific decadal variability with information regarding long-term changes in water mass age and coastal ocean circulation. Finally, existing tree-ring chronologies from the North Pacific rim will be integrated with the geoduck data to maximize reconstruction power and accuracy in a multi-proxy approach. The broader impacts involve support for an early career scientist, grad student, and post-doc, and will involve undergraduate students in the research activities. The research aims to provide useful insights into PDO variability, the reasons for divergence among regional tree ring records, the environmental settings of native cultures and fisheries in the past, and insights into marine reservoir effects. If achieved, these would be important scientific impacts. The proposal has an element of risk but that risk is offset by the potential benefit in new scientific understanding.