Varve data from a sediment profile of Lake Woserin, Germany

Time-series of varve properties and geochemistry were established from varved sediments of Lake Woserin (north-eastern Germany) covering the recent period AD 2010-1923 and the Mid-Holocene time-window 6400-4950 varve years before present (vyr BP) using microfacies analyses, X-ray fluorescence scanning (µ-XRF), microscopic varve chronology and 14C dating. The microscopic varve chronology was compared to a macroscopic varve chronology for the same sediment interval. Calcite layer thickness during the recent period is significantly correlated to increases in local annual precipitation (r=0.46, p=0.03) and reduced air-pressure (r=-0.72, p<0.0001). Meteorologically consistent with enhanced precipitation at Lake Woserin, a composite 500 hPa anomaly map for years with >1 standard deviation calcite layer thickness depicts a negative wave train air-pressure anomaly centred over southern Europe, with north-eastern Germany at its northern frontal zone. Three centennial-scale intervals of thicker calcite layers around the Mid-Holocene periods 6200-5900, 5750-5400 and 5300-4950 vyr BP might reflect humid conditions favouring calcite precipitation through the transport of Ca2+ ions into Lake Woserin, synchronous to wetter conditions in Europe. Calcite layer thickness oscillations of about 88 and 208 years resemble the solar Gleissberg and Suess cycles suggesting that the recorded hydroclimate changes in north-eastern Germany are modified by solar influences on synoptic-scale atmospheric circulation. However, parts of the periods of thicker calcite layers around 5750-5400 and 5200 vyr BP also coincide to enhanced human catchment activity at Lake Woserin. Therefore, calcite precipitation during these time-windows might have further been favored by anthropogenic deforestation mobilizing Ca2+ ions and/or lake eutrophication.

本研究通过微相分析、X射线荧光扫描（µ-XRF）、显微纹泥（varve）年代学与14C测年方法，对德国东北部沃瑟林湖的纹层沉积物开展研究，建立了覆盖公元2010-1923年近代时段以及中全新世6400~4950纹泥年距现今（vyr BP）时间窗口的纹泥属性与地球化学时间序列。针对同一沉积物层位，研究人员将显微纹泥年代学与宏观纹泥年代学进行了对比。近代时段内的方解石层厚度与当地年降水量增幅（相关系数r=0.46，p=0.03）以及气压降低（r=-0.72，p<0.0001）呈显著相关关系。在气象学上与沃瑟林湖降水量增加相一致的是，对方解石层厚度超过1倍标准差的年份合成的500百帕气压异常图显示，存在以欧洲南部为中心的负波列气压异常，德国东北部位于该异常的北部锋区。中全新世时期存在三个百年尺度的方解石层增厚时段，分别为6200~5900、5750~5400以及5300~4950 vyr BP，这些时段可能对应湿润气候环境：钙离子（Ca²+）输入沃瑟林湖，促进了方解石沉淀，这与欧洲全域的湿润气候阶段同步。方解石层厚度的约88年与208年周期振荡，与太阳活动的格莱斯贝格周期（Gleissberg cycle）与苏斯周期（Suess cycle）相吻合，这表明德国东北部记录的水文气候变化，受到太阳活动通过影响天气尺度大气环流所带来的调制作用。但在5750~5400以及5200 vyr BP的部分方解石层增厚时段，也与沃瑟林湖流域人类活动强度的增强相重合。因此，在这些时间窗口内，方解石沉淀可能还受到人为砍伐森林（活化钙离子）以及/或湖泊富营养化的进一步促进。