Abstract
In semi-arid regions of the world, knowledge about the long-term hydroclimate variability is essential to analyze and evaluate the impact of current climate change on ecosystems. We present the first tree-ring δ18O based hydroclimatic reconstruction for northern semi-arid Iran spanning the period 1515–2015. A highly significant correlation between tree-ring δ18O variations of juniper trees and spring (April–June) precipitation reveals a major influence of spring water availability during the early growing season. The driest period of the past 501 years occurred in the 16th century while the 18th century was the wettest, during which the overall highest frequency of wet year events occurred. A gradual decline in spring precipitation is evident from the beginning of the 19th century, pointing to even drier climate conditions. The analysis of dry/wet events indicates that the frequency of years with relatively dry spring increased over the last three centuries, while the number of wet events decreased. Our findings are in accordance with historical Persian disaster records (e.g., the severe droughts of 1870–1872, 1917–1919; severe flooding of 1867, the 1930s, and 1950). Correlation analyses between the reconstruction and different atmospheric circulation indices revealed no significant influence of large-scale drivers on spring precipitation in northern Iran.
Highlights
Iran is located in western Asia, in one of the world’s most water-scarce and dry regions of the Middle East [1,2]
In previous methodological studiesthe evaluating common signal betweenisotope individual series trees and the suitability of different pooling methods, we demonstrated that this number of that treesthis and from juniper trees [29] and the suitability of different pooling methods, we demonstrated the approach of inter-tree is the best alternative to individual-tree isotope measurements number of trees and the pooling approach of inter-tree pooling is the best alternative to individual-tree isotope measurements [59]
We developed a multi-century tree-ring stable oxygen isotope chronology from J. polycarpos and
Summary
Iran is located in western Asia, in one of the world’s most water-scarce and dry regions of the Middle East [1,2]. Due to its geographic location between the arid to the semi-arid mid-latitude belt and the subtropical zone, and complex topography, Iran is highly sensitive to climate change [3]. 85% of the Iranian land area is characterized by arid or semi-arid conditions, underlining the vulnerability of the region to climate change, especially to changes in hydroclimate [4,5,6]. The timing of maximum precipitation in northern Iran is postulated to shift from April to November, which will very likely affect the regional water supply during the growing season [7]
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