Preliminary reconstructions of spring precipitation in southwestern Turkey from tree‐ring width

Abstract

Two reconstructions of spring (May-June) precipitation have been developed for southwestern Turkey. The first reconstruction (1776-1998) was developed from principal components of nine chronologies of Cedrus libani, Juniperus excelsa, Pinus brutia, and Pinus nigra. The second reconstruction (1339-1998) was derived from principal components of three J. excelsa chronologies. Calibration and verification statistics of both reconstructions indicate reasonably accurate reconstruction of spring precipitation for southwestern Turkey, and show clear evidence of multi-year to decadal variations in spring precipitation. The longest period of reconstructed spring drought, defined as consecutive years with less than 80% of normal May-June precipitation, was 4 years (1476-79). Only one drought event of this duration has occurred during the last six centuries. Monte Carlo analysis indicates a less than 33% probability that southwestern Turkey has experienced spring drought longer than 5 years in the past 660 years. Apart from the 1476-79 extended dry period, spring droughts of 3 years in length have only occurred from 1700 to the present. The longest reconstructed wet period, defined as consecutive years with more than 120% of normal May-June precipitation, was 4 years (1532-35). The absence of extended spring drought during the 16th and 17th centuries and the occurrence of extended wet spring periods during these centuries suggest a possible regime shift in climate. Preliminary analysis of links between large-scale climatic variation and these climate reconstructions shows that there is a relationship between extremes in spring precipitation and anomalous atmospheric circulation in the region.

Tree‐ring reconstructions of precipitation and streamflow for north‐western Turkey

“…The longest interval between dry events is 22 years , with a mean period between events of ∼5 years. As noted, the region is generally humid, and this observed duration of dry years is less than, for example, that found for the Mediterranean region (Touchan et al, 2003). The frequency of dry years is about the same with the Mediterranean region, where Touchan et al (2003) computed a mean drought recurrence interval of 4.8 years.…”

“…Hughes et al (2001) found that extreme signature years in tree-ring data from the Aegean region (including northern Turkey, Greece and Georgia) coincided with recorded April-June precipitation and sea level pressure anomalies. Touchan et al (2003Touchan et al ( , 2005a demonstrated correspondence between Turkish tree-rings and atmospheric circulation patterns during extreme years. Although Touchan et al's study partly overlaps that reported herein, they did not include data from our immediate north-western Turkey study region.…”

“…This method has been used previously in dendroclimatological reconstructions for Turkey (Touchan et al, 2003(Touchan et al, , 2005a.…”

“…Both reconstructions primarily emphasize high-frequency fluctuations, and thus decadal or longer-term trends in precipitation or streamflow were not retained in this analysis and were not discussed herein. In order to investigate extreme drought and flood events in the reconstructions, we used positive and negative anomaly thresholds, defined (as previously noted) as those exceeding 85 (86 mm) and 115% (116 mm), respectively (Touchan et al, 2003(Touchan et al, , 2005a.…”

“…For Turkey and surrounding areas of the Middle East, however, there have been relatively few such studies, although this situation has improved considerably in recent years (e.g. for Turkey: D'Arrigo and Cullen, 2001;Hughes et al, 2001;Touchan et al, 2003;Touchan et al, 2005a,b;and for Jordan: Touchan and Hughes, 1999;. These recent efforts have focused mainly on reconstructing seasonal or annual indices of precipitation, or on investigations of anomalous climate years.…”