80
R.D . D'Arrigo and a.c. Jacoby
The sign and magnitude of ENSO influence on temperature and precipitation vary along a gradient from coastal Alaska down the coast to
British Columbia and south to California (Yarnal & Diaz, 1986). Correlation analysis of the four sets of Pacific Northwest chronologies with
ENSO indices (e.g., the Southern Oscillation Index or pressure differential between Tahiti and Darwin in the equatorial Pacific) indicated
that tree growth tends to be significantly above average during warm
ENSO events. These warm events are often associated with a deepened
Aleutian low and warmer conditions near Vancouver Island and along the
British Columbia and Washington state coastlines (Yarnal & Diaz, 1986).
The tree-ring data from the Pacific Northwest could thus prove useful in a
comparative study of past ENSO variability along the western coastlines
of North and South America. Such a study would also complement
transects proposed for AMIGO that aim to compare Vancouver Island
with a comparable site in Chile.
Winter Precipitation Reconstruction for Northwestern
New Mexico
A lOOO-year reconstruction of November-May winter precipitation for
northwestern New Mexico was developed by D'Arrigo and Jacoby (1991).
This reconstruction was based on six tree-ring width chronologies, including both living and archaeological data for several coniferous species
(Dean, 1988; Dean & Robinson, 1978). Other researchers have also
related tree rings to precipitation variations in the southwest United
States (e.g., Meko, Stockton, & Boggess, 1980), a semiarid region with
significant precipitation inputs from the Pacific Ocean.
The southwestern United States is another region of known ENSO
teleconnection (Ropelewski & Halpert, 1987), with above- or belowaverage winter precipitation associated with warm or cold events respectively. Features of the New Mexico reconstruction (D'Arrigo &
Jacoby, 1991) include two prolonged drought periods during the broadly
defined cold period known as the Little Ice Age (Grove, .1,988). One
might speculate that these dry periods reflect more pronounced coldevent (La Nina) conditions, although additional paleoclimatic data are
needed to confirm this possibility.
Related Studies
Briffa et al. (1992) reconstructed patterns of summer temperature (April
to September) since 1600 based on maximum-latewood density chronologies from the Schweingruber data base for western North America. A
principal-components-regression technique was employed to compare 53
high-elevation density series to temperature. Briffa et al. (1992) found
R.D . D'Arrigo and a.c. Jacoby
The sign and magnitude of ENSO influence on temperature and precipitation vary along a gradient from coastal Alaska down the coast to
British Columbia and south to California (Yarnal & Diaz, 1986). Correlation analysis of the four sets of Pacific Northwest chronologies with
ENSO indices (e.g., the Southern Oscillation Index or pressure differential between Tahiti and Darwin in the equatorial Pacific) indicated
that tree growth tends to be significantly above average during warm
ENSO events. These warm events are often associated with a deepened
Aleutian low and warmer conditions near Vancouver Island and along the
British Columbia and Washington state coastlines (Yarnal & Diaz, 1986).
The tree-ring data from the Pacific Northwest could thus prove useful in a
comparative study of past ENSO variability along the western coastlines
of North and South America. Such a study would also complement
transects proposed for AMIGO that aim to compare Vancouver Island
with a comparable site in Chile.
Winter Precipitation Reconstruction for Northwestern
New Mexico
A lOOO-year reconstruction of November-May winter precipitation for
northwestern New Mexico was developed by D'Arrigo and Jacoby (1991).
This reconstruction was based on six tree-ring width chronologies, including both living and archaeological data for several coniferous species
(Dean, 1988; Dean & Robinson, 1978). Other researchers have also
related tree rings to precipitation variations in the southwest United
States (e.g., Meko, Stockton, & Boggess, 1980), a semiarid region with
significant precipitation inputs from the Pacific Ocean.
The southwestern United States is another region of known ENSO
teleconnection (Ropelewski & Halpert, 1987), with above- or belowaverage winter precipitation associated with warm or cold events respectively. Features of the New Mexico reconstruction (D'Arrigo &
Jacoby, 1991) include two prolonged drought periods during the broadly
defined cold period known as the Little Ice Age (Grove, .1,988). One
might speculate that these dry periods reflect more pronounced coldevent (La Nina) conditions, although additional paleoclimatic data are
needed to confirm this possibility.
Related Studies
Briffa et al. (1992) reconstructed patterns of summer temperature (April
to September) since 1600 based on maximum-latewood density chronologies from the Schweingruber data base for western North America. A
principal-components-regression technique was employed to compare 53
high-elevation density series to temperature. Briffa et al. (1992) found