Geoscience Reference
In-Depth Information
18
O-
derived modeled data with respect to the 1951-1980 instrumental mean. Smoothed curves (5-year
Kernel filters) are shown for the
Fig. 6.3
(
a
) Annual precipitation values (AD 1898-1990) from instrumental and tree-ring
δ
18
O(
thick black
) and instrumental (
dashed gray
) series. (
b
)
δ
18
O-based precipitation reconstruction since AD 950. Proxy data were calibrated by using a
linear regression over the time period AD 1898-1990. The raw
The
δ
18
O series is inverted owing to the
negative sign of the regression slope. The
horizontal line
is the overall mean of the reconstruction.
For the period AD 1264-1599, maximum deviations are shown in
black
, when using data only from
old tree rings. Replication of the reconstruction is three trees (six cores) at AD 950. Long-term
variations are highlighted by using a 150-year spline (
thick black curve
). Uncertainty estimates
for the low-frequency domain are indicated by two standard errors. Adapted by permission from
δ
on a correlation of
r
0.001) with September-
effects of developing reconstructions from different age classes of trees and found
that little age-related bias was imparted into the reconstruction, though they note a
slight change in the high-frequency component when only juvenile trees are used.
However, the low-frequency components of the reconstruction are unaffected by
tree age. The reconstruction is spatiotemporally robust, with the same signal being
captured at various ecologically distinct sites, and at decadal to centennial scales.
The record also shows coherence with other proxy records across the Northern
=
0.58 (AD 1898-1990,
P
<
