A long-term drought reconstruction based on oxygen isotope tree ring data for central and eastern parts of Europe (Romania)

<p>This study investigates the relationship between oxygen isotope ratios (<span class="inline-formula"><i>δ</i><sup>18</sup></span>O) in oak tree ring cellulose and past drought variability in Letea Forest, Romania. A <span class="inline-f...

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Main Authors: V. Nagavciuc, G. Helle, M. Rădoane, C.-C. Roibu, M.-G. Cotos, M. Ionita
Format: Article
Language:English
Published: Copernicus Publications 2025-01-01
Series:Biogeosciences
Online Access:https://bg.copernicus.org/articles/22/55/2025/bg-22-55-2025.pdf
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author V. Nagavciuc
V. Nagavciuc
G. Helle
M. Rădoane
C.-C. Roibu
M.-G. Cotos
M. Ionita
M. Ionita
author_facet V. Nagavciuc
V. Nagavciuc
G. Helle
M. Rădoane
C.-C. Roibu
M.-G. Cotos
M. Ionita
M. Ionita
author_sort V. Nagavciuc
collection DOAJ
description <p>This study investigates the relationship between oxygen isotope ratios (<span class="inline-formula"><i>δ</i><sup>18</sup></span>O) in oak tree ring cellulose and past drought variability in Letea Forest, Romania. A <span class="inline-formula"><i>δ</i><sup>18</sup></span>O site chronology spanning 1803–2020 was compiled from seven individual time series. <span class="inline-formula"><i>δ</i><sup>18</sup></span>O values exhibited a significant negative correlation with moisture-related variables (cloud cover, relative humidity, and precipitation) and a positive correlation with temperature and sunshine duration. This confirms that <span class="inline-formula"><i>δ</i><sup>18</sup></span>O from tree rings can be a good proxy for moisture availability. The strongest correlation was found between <span class="inline-formula"><i>δ</i><sup>18</sup></span>O and the August Standardized Precipitation Evapotranspiration Index for an accumulation period of 9 months (SPEI9) for central and eastern Europe. This highlights SPEI9 as a superior indicator of drought compared to individual parameters like temperature or precipitation. Using a linear regression model, we reconstructed August SPEI9 variability for the past 200 years. The reconstruction captured interannual and decadal variations, with distinct wet and dry periods. Analysis of large-scale atmospheric circulation patterns revealed a link between high <span class="inline-formula"><i>δ</i><sup>18</sup></span>O values (indicating dry conditions) and a high-pressure system over the North Atlantic. Conversely, low <span class="inline-formula"><i>δ</i><sup>18</sup></span>O values (indicating wet conditions) corresponded to negative pressure anomalies over Europe. Moreover, extreme values of <span class="inline-formula"><i>δ</i><sup>18</sup></span>O are also associated with the prevalence of a hemispheric teleconnection pattern, namely wave number 4. This <span class="inline-formula"><i>δ</i><sup>18</sup></span>O chronology and the corresponding August SPEI9 reconstruction offer valuable tools for understanding past climate variability and its relationship with large-scale atmospheric and oceanic circulation patterns.</p>
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publishDate 2025-01-01
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series Biogeosciences
spelling doaj-art-df1a5867149747a999c54734f36aedc12025-01-07T08:14:15ZengCopernicus PublicationsBiogeosciences1726-41701726-41892025-01-0122556910.5194/bg-22-55-2025A long-term drought reconstruction based on oxygen isotope tree ring data for central and eastern parts of Europe (Romania)V. Nagavciuc0V. Nagavciuc1G. Helle2M. Rădoane3C.-C. Roibu4M.-G. Cotos5M. Ionita6M. Ionita7Paleoclimate Dynamics, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven 27570, GermanyForest Biometrics Laboratory – Faculty of Forestry, “Stefan cel Mare” University of Suceava, Universităţii Street No. 13, Suceava 720229, RomaniaGerman Research Centre for Geosciences GFZ, 4.3 Climate Dynamics and Landscape Evolution, Telegrafenberg, Potsdam 14473, GermanyForest Biometrics Laboratory – Faculty of Forestry, “Stefan cel Mare” University of Suceava, Universităţii Street No. 13, Suceava 720229, RomaniaForest Biometrics Laboratory – Faculty of Forestry, “Stefan cel Mare” University of Suceava, Universităţii Street No. 13, Suceava 720229, RomaniaForest Biometrics Laboratory – Faculty of Forestry, “Stefan cel Mare” University of Suceava, Universităţii Street No. 13, Suceava 720229, RomaniaPaleoclimate Dynamics, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven 27570, GermanyForest Biometrics Laboratory – Faculty of Forestry, “Stefan cel Mare” University of Suceava, Universităţii Street No. 13, Suceava 720229, Romania<p>This study investigates the relationship between oxygen isotope ratios (<span class="inline-formula"><i>δ</i><sup>18</sup></span>O) in oak tree ring cellulose and past drought variability in Letea Forest, Romania. A <span class="inline-formula"><i>δ</i><sup>18</sup></span>O site chronology spanning 1803–2020 was compiled from seven individual time series. <span class="inline-formula"><i>δ</i><sup>18</sup></span>O values exhibited a significant negative correlation with moisture-related variables (cloud cover, relative humidity, and precipitation) and a positive correlation with temperature and sunshine duration. This confirms that <span class="inline-formula"><i>δ</i><sup>18</sup></span>O from tree rings can be a good proxy for moisture availability. The strongest correlation was found between <span class="inline-formula"><i>δ</i><sup>18</sup></span>O and the August Standardized Precipitation Evapotranspiration Index for an accumulation period of 9 months (SPEI9) for central and eastern Europe. This highlights SPEI9 as a superior indicator of drought compared to individual parameters like temperature or precipitation. Using a linear regression model, we reconstructed August SPEI9 variability for the past 200 years. The reconstruction captured interannual and decadal variations, with distinct wet and dry periods. Analysis of large-scale atmospheric circulation patterns revealed a link between high <span class="inline-formula"><i>δ</i><sup>18</sup></span>O values (indicating dry conditions) and a high-pressure system over the North Atlantic. Conversely, low <span class="inline-formula"><i>δ</i><sup>18</sup></span>O values (indicating wet conditions) corresponded to negative pressure anomalies over Europe. Moreover, extreme values of <span class="inline-formula"><i>δ</i><sup>18</sup></span>O are also associated with the prevalence of a hemispheric teleconnection pattern, namely wave number 4. This <span class="inline-formula"><i>δ</i><sup>18</sup></span>O chronology and the corresponding August SPEI9 reconstruction offer valuable tools for understanding past climate variability and its relationship with large-scale atmospheric and oceanic circulation patterns.</p>https://bg.copernicus.org/articles/22/55/2025/bg-22-55-2025.pdf
spellingShingle V. Nagavciuc
V. Nagavciuc
G. Helle
M. Rădoane
C.-C. Roibu
M.-G. Cotos
M. Ionita
M. Ionita
A long-term drought reconstruction based on oxygen isotope tree ring data for central and eastern parts of Europe (Romania)
Biogeosciences
title A long-term drought reconstruction based on oxygen isotope tree ring data for central and eastern parts of Europe (Romania)
title_full A long-term drought reconstruction based on oxygen isotope tree ring data for central and eastern parts of Europe (Romania)
title_fullStr A long-term drought reconstruction based on oxygen isotope tree ring data for central and eastern parts of Europe (Romania)
title_full_unstemmed A long-term drought reconstruction based on oxygen isotope tree ring data for central and eastern parts of Europe (Romania)
title_short A long-term drought reconstruction based on oxygen isotope tree ring data for central and eastern parts of Europe (Romania)
title_sort long term drought reconstruction based on oxygen isotope tree ring data for central and eastern parts of europe romania
url https://bg.copernicus.org/articles/22/55/2025/bg-22-55-2025.pdf
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