title: Pacific North American circulation pattern links external forcing and North American hydroclimatic change over the past millennium.
abstract: Land and sea surface temperatures, precipitation, and storm tracks in North America and the North Pacific are controlled to a large degree by atmospheric variability associated with the Pacific North American (PNA) pattern. The modern instrumental record indicates a trend toward a positive PNA phase in recent decades, which has led to accelerated warming and snowpack decline in northwestern North America. The brevity of the instrumental record, however, limits our understanding of long-term PNA variability and its directional or cyclic patterns. Here we develop a 937-y-long reconstruction of the winter PNA based on a network of annually resolved tree-ring proxy records across North America. The reconstruction is consistent with previous regional records in suggesting that the recent persistent positive PNA pattern is unprecedented over the past millennium, but documents patterns of decadal-scale variability that contrast with previous reconstructions. Our reconstruction shows that PNA has been strongly and consistently correlated with sea surface temperature variation, solar irradiance, and volcanic forcing over the period of record, and played a significant role in translating these forcings into decadal-to-multidecadal hydroclimate variability over North America. Climate model ensembles show limited power to predict multidecadal variation in PNA over the period of our record, raising questions about their potential to project future hydroclimatic change modulated by this circulation pattern.
authors.affiliation: State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China; gabe.bowen@utah.edu liuzf406@gmail.com.
authors.forename: Zhongfang
authors.initials: Z
authors.lastname: Liu
authors.affiliation: School of Mathematical Sciences, Tongji University, Shanghai 200092, China.
authors.forename: Yanlin
authors.initials: Y
authors.lastname: Tang
authors.affiliation: State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China.
authors.forename: Zhimin
authors.initials: Z
authors.lastname: Jian
authors.affiliation: Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Poulsen
authors.affiliation: Department of Biological Sciences, University of Alaska Anchorage, Anchorage, AK 99508.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Welker
authors.affiliation: Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112; gabe.bowen@utah.edu liuzf406@gmail.com.|Global Change and Sustainability Center, University of Utah, Salt Lake City, UT 84112.
authors.forename: Gabriel J
authors.identifier: 0000-0002-6928-3104
authors.initials: GJ
authors.lastname: Bowen
keywords: Holocene; North America; atmospheric circulation; climate change; paleoclimate