North Pacific Decadal Climate
Variability Since AD 1661

North Pacific Decadal Climate
Variability Since AD 1661

Journal of Climate, Volume 14, Number 1, pp. 5-10, January 2001.

Franco Biondi
Department of Geography, University of Nevada.
Alexander Gershunov
Scripps Institute of Oceanography
Daniel R. Cayan
Scripps Institute of Oceanography and US Geological Survey

Climate in the North Pacific and North American sectors has experienced interdecadal shifts during the 20th century. A network of recently developed tree-ring chronologies for Southern and Baja California extends the instrumental record, and reveals decadal-scale variability back to AD 1661. The Pacific Decadal Oscillation (PDO) is closely matched by the dominant mode of tree-ring variability, which provides a preliminary view of multi-annual climate fluctuations spanning the past four centuries. The reconstructed PDO index features a prominent bidecadal oscillation, whose amplitude weakened in the late 1700s to mid-1800s. A comparison with proxy records of ENSO suggests that the greatest decadal-scale oscillations in Pacific climate between 1706 and 1977 occurred around 1750, 1905, and 1947.

Download the Reconstructed PDO time series and
description from the WDC Paleo Archive.

Download the tree-ring data used in this study:
(Available upon publication).
Jeffrey Pine sites (stars):
Fish Creek Trail (San Gorgonio) Chronology and measurements
La Tasajera (San Pedro Martir) Chronology and measurements
Mt. Laguna Chronology and measurements

Big-cone Douglas-fir sites (squares):
Fry Creek (Palomar Mt.) Chronology and measurements
Pine Mountain North Chronology and measurements
Santa Ana Mountains Chronology and measurements

To read or view the full study, please visit the American Meteorological Society website.
It was published in Journal of Climate Volume 14, Number 1, pp. 5-10, January 2001.

Fig. 2 (upper)
Interdecadal variability of
tree-ring chronologies closely
matches the PDO since about 1925,
especially with regard to the major reversals
in 1947 and 1977 (dashed vertical lines).

Fig. 2 (lower) At decadal scales,
the leading mode of tree-ring
variability (PC1, dotted)
well represents PDO patterns (solid).
Reconstructed PDO since 1660.
Correlation between instrumental (dashed) and
reconstructed PDO is 0.64 from 1925 to 1991.
During warm periods, the eastern North Pacific
is warmer than usual, and the central North Pacific
is cooler (viceversa during cool periods). Warm and
cool PDO phases are qualitatively similar to warm
and cool ENSO events, but different because of slower
temporal dynamics and stronger midlatitudinal responses.

Fig. 4A. (above left) In the common period 1900-1991, the instrumental and reconstructed PDO are spectrally coherent in the bidecadal band.

Fig 4B. (above right) The two leading eigenfunctions (EOFs) of reconstructed PDO form an oscillatory pair (thick line: first EFO) that accounts for 28.5% of variance. The combined amplitude of those two components has a ~23 year period, and represents the time-varying strength of the bidecadal oscillation.

Fig 4C. (below) Evolutive spectrum of reconstructed PDO, showing a prominent bidecadal mode whose strength was less intense from the late 1700s to the mid-1800s. Lower frequencies (from multidecadal to centennial and longer) in the PDO time series are restricted to the twentieth century.

Fig. 5 (below) PDO-ENSO patterns from 1706 to 1977, obtained by adding the proxy PDO record (Fig. 3) with a proxy record of winter Southern Oscillation Index derived by Stahle et al. (1998) Both series were first converted to standard deviation units, and the sign of the SOI was reversed to make El Nino years positive. Absolute values are higher (lower) during constructive (destructive) interference between PDO and ENSO.

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12 Jan 2001