Ocean-atmosphere forcing of centennial hydroclimate variability in the Pacific Northwest

B. A. Steinman, M. B. Abbott, M. E. Mann, J. Ortiz, S. Feng, D. P. Pompeani, N. D. Stansell, L. Anderson, B. P. Finney, and B. W. Bird

Geophysical Research Letters (16 April 2014)

DOI: 10.1002/2014GL059499

Reconstructing centennial timescale hydroclimate variability during the late Holocene is critically important for understanding large-scale patterns of drought and their relationship with climate dynamics. We present sediment oxygen isotope records spanning the last two millennia from 10 lakes, as well as climate model simulations, indicating that the Little Ice Age was dry relative to the Medieval Climate Anomaly in much of the Pacific Northwest of North America. This pattern is consistent with observed associations between the El Niño–Southern Oscillation (ENSO), the Northern Annular Mode, and drought as well as with proxy-based reconstructions of Pacific and Atlantic ocean-atmosphere variations over the past 1000 years. The large amplitude of centennial variability indicated by the lake data suggests that regional hydroclimate is characterized by longer-term shifts in ENSO-like dynamics and that an improved understanding of the centennial timescale relationship between external forcing and drought is necessary for projecting future hydroclimatic conditions in western North America.

keywords: paleoclimatology; isotope geochemistry; Little Ice Age; paleolimnology; lake sediment; Medieval Climate Anomaly; 0473 Paleoclimatology and paleoceanography; 1041 Stable isotope geochemistry; 1616 Climate variability; 1626 Global climate models; 1833 Hydroclimatology

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