Geoscience Reference
In-Depth Information
la Muerte. In recent years, new collections have been carried out in these sites
to update and extend these chronologies, especially by collecting preserved
matic signal related to winter-spring precipitation during the previous and
current growing seasons. A composite record consisting of El Asiento and El
estimates of June-December precipitation for central Chile extending from
The reconstruction suggests that the decadal variability of precipitation
in central Chile was greater before the twentieth century, with more intense
and prolonged dry and wet episodes. Multiyear drought episodes in the eigh-
teenth, seventeenth, sixteenth, and fourteenth centuries exceed the estimates
of decadal drought during the twentieth century. The reconstruction also indi-
cates an increase in interannual variability after 1850. In fact, the risk of
drought exceeding all thresholds increases dramatically in the reconstructed
precipitation series after 1850, consistent with the drying trends indicated by
selected long instrumental precipitation records.
—Carlos LeQuesne and David Stahle
Box Fig. 7.16
Tree-ring-reconstructed precipitation for central Chile from AD 1200 to
2000. A cubic smoothing spline highlighting multidecadal variability (ca. 25 years, fit for
the period 1205-1995) and the
±
1.0 standard deviation thresholds are also plotted
It is important to note that based on instrumental records, the strongest telecon-
nections between precipitation in the southern United States-northern Mexico and
SST in the tropical Pacific have been identified for the winter months (Kiladis and
tions are reflecting drought conditions during the summer months. On the other
hand, the
Polylepis
chronologies in the Bolivian highlands and the
Austrocedrus
chronologies in central Chile are sensitive to summer and winter precipitation,
respectively. Despite the limitation imposed by the differences in seasonal-
window responses of trees from different regions to precipitation and the fact
