Climatic context and ecological implications of summer fog decline in the coast redwood region
- aDepartment of Environmental Science, Policy, and Management, and
- bDepartment of Integrative Biology, University of California, Berkeley, CA 94720
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Communicated by Inez Y. Fung, University of California, Berkeley, CA, January 7, 2010 (received for review August 10, 2009)
Abstract
Biogeographical, physiological, and paleoecological evidence suggests that the coast redwood [Sequoia sempervirens (D. Don) Endl.] is closely associated with the presence of summer marine fog along the Pacific coast of California. Here we present a novel record of summer fog frequency in the coast redwood region upon the basis of direct hourly measurements of cloud ceiling heights from 1951 to 2008. Our analysis shows that coastal summer fog frequency is a remarkably integrative measure of United States Pacific coastal climate, with strong statistical connections to the wind-driven upwelling system of the California Current and the broad ocean temperature pattern known as the Pacific Decadal Oscillation. By using a long-term index of daily maximum land temperatures, we infer a 33% reduction in fog frequency since the early 20th century. We present tree physiological data suggesting that coast redwood and other ecosystems along the United States west coast may be increasingly drought stressed under a summer climate of reduced fog frequency and greater evaporative demand.
Footnotes
- 1To whom correspondence should be addressed. E-mail: jajstone{at}berkeley.edu.
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Author contributions: J.A.J. and T.E.D. designed research; J.A.J. performed research; J.A.J. analyzed data; and J.A.J. and T.E.D. wrote the paper.
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The authors declare no conflict of interest.
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This article contains supporting information online at www.pnas.org/cgi/content/full/0915062107/DCSupplemental.
Freely available online through the PNAS open access option.
