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Holocene hydroclimate changes in continental Croatia recorded in speleothem δ13C and δ18O from Nova Grgosova Cave
The Holocene ( IF 2.4 ) Pub Date : 2021-07-01 , DOI: 10.1177/09596836211019120
Maša Surić 1 , Andrea Columbu 2 , Robert Lončarić 1 , Petra Bajo 3 , Neven Bočić 4 , Nina Lončar 1 , Russell N Drysdale 5 , John C Hellstrom 6
Affiliation  

We present the first stable isotope (δ13C and δ18O) speleothem record from continental Croatia retrieved from two coeval stalagmites from Nova Grgosova Cave. U-Th dates constrain the stalagmite growth history from 10 ka to the present, revealing coeval growth between 7.8 and 5.6 ka. We interpret δ18O as an autumn/winter hydrological proxy related to changes of vapor source, precipitation amount, and/or seasonal rainfall distribution, while δ13C predominantly responds to spring/summer vegetation status and soil microbial activity. We identify several centennial to millennial-scale hydroclimate oscillations during this period that result from multiple forcing factors. Along with amount and source effect, it appears that some centennial variations were governed also by seasonal moisture balance. From 9.2 to 8.8 ka BP, the local environmental setting was characterized by enhanced vegetation activity, while during the 8.2 ka event the main feature was a change in precipitation seasonality. The most prominent change, identified in both δ13C records, is a sudden decline of vegetation and soil biological activity around 7.4 ka, indicating a precipitation decrease at a time of maximum plant growth in spring and summer and likely also reduced precipitation in autumn and winter. Although small in magnitude in these speleothems, a peak in δ18O and δ13C values at 4.3–4.1 ka suggests that both summer and winter conditions were substantially drier during the 4.2 ka event, in accordance with increased Mediterranean aridity and consistent with other global climate changes reported at this time. Compared to the present North Atlantic Oscillation (NAO) influence, we assume that millennial Holocene NAO-like variations were persistent through the Holocene via their effect on modifying local/regional air temperature, vapor origin, and inter- and intrannual precipitation distribution. Anthropogenic deforestation, which was the first major human impact on the environment during the Neolithic agricultural revolution, is excluded as a leading factor in δ13C variability since the first sedentary settlements were established further to the east in more arable locations along river valleys. However, the impact of intensive mining around the cave site during the last millennium is evident, with substantial deforestation driving an increase in δ13C.



中文翻译:

Nova Grgosova 洞穴洞穴中记录的克罗地亚大陆全新世水文气候变化 δ 13 C 和 δ 18 O

我们展示了克罗地亚大陆的第一个稳定同位素(δ 13 C 和 δ 18 O)洞穴记录,这些记录是从 Nova Grgosova 洞穴的两个同时代石笋中提取的。U-Th 日期限制了从 10 ka 到现在的石笋生长历史,揭示了 7.8 和 5.6 ka 之间的同期生长。我们将 δ 18 O解释为与水汽源、降水量和/或季节性降雨分布变化相关的秋/冬水文代理,而 δ 13C 主要对春季/夏季植被状况和土壤微生物活动作出反应。我们确定了在此期间由多种强迫因素引起的几个百年到千禧年规模的水文气候振荡。除了数量和来源效应外,某些百年变化似乎也受季节性水分平衡的影响。从 9.2 到 8.8 ka BP,当地环境背景以植被活动增强为特征,而在 8.2 ka 事件期间,主要特征是降水季节性的变化。最显着的变化,分别在 δ 13C 记录,是植被和土壤生物活动在 7.4 ka 左右突然下降,表明在春季和夏季植物生长最大时降水减少,秋季和冬季也可能减少降水。虽然这些洞穴中的量级很小,但 δ 18 O 和 δ 13 中的峰值4.3-4.1 ka 的 C 值表明,在 4.2 ka 事件期间,夏季和冬季的条件都显着干燥,这与地中海干旱增加并与此时报告的其他全球气候变化一致。与目前的北大西洋涛动 (NAO) 影响相比,我们假设千禧年的全新世 NAO 样变化通过其对改变局部/区域气温、蒸汽起源以及年际和年际降水分布的影响在全新世中持续存在。人为砍伐森林是新石器时代农业革命期间人类对环境的第一个主要影响,被排除在 δ 13的主要因素之外自从第一个定居定居点在更远的东部沿河谷更可耕种的地方建立以来的 C 变化。然而,在过去的千年中,洞穴遗址周围密集采矿的影响是显而易见的,大量森林砍伐导致 δ 13 C增加。

更新日期:2021-07-01
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