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首页> 外文期刊>The holocene >Biogeochemical evidence for hydrologic changes during the Holocene in a lake sediment record from southeast Greenland
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Biogeochemical evidence for hydrologic changes during the Holocene in a lake sediment record from southeast Greenland

机译：全新世期间格陵兰东南部湖泊沉积物中的水文变化的生物地球化学证据

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Holocene paleoclimate records from Greenland help us understand the response of the Greenland Ice Sheet and regional oceanic and atmospheric circulation systems to natural climate variability in order to place recent changes in a longer-term perspective. Here biogeochemical analysis of a lake sediment core from southeast Greenland is used to define changes in moisture balance and runoff during the Holocene in a catchment near the margin of the Greenland Ice Sheet. A 1.6 m sediment core that spans the last 8.8 ka was recovered from Flower Valley Lake on Ammassalik Island. Magnetic susceptibility, diatoms, bulk biogeochemical properties (TOC, C/N, δ~(13)C_(org)), and lipid biomarkers (n-alkanes; C_(16)-C_(31),) reveal changes in clastic sedimentation and the relative input of terrestrial- and aquatic-derived organic matter. Hydrogen isotope values (δD) of mid- (n-C_(25)) and long-chain (n-C_(29), n-C_(31)) n-alkanes allow reconstruction of δD of precipitation and summertime evaporation of lake water. Following a period of early lake ontogeny and landscape stabilization after deglaciation from 8.4 to 7.0 ka, the mid Holocene, 8.4-4.1 ka, is characterized by greater evaporative enrichment of the lake water as indicated by δD records. After 4.1 ka, there is a decrease in evaporative enrichment of the lake water. There is also an abrupt transition to more variable sedimentation marked by sharp increases in magnetic susceptibility, C/N, δ~(13)C_(org), and the concentration of long-chain n-alkanes, showing periodic delivery of terrestrial organic matter and clastic sediment to the lake. Higher insolation during the mid Holocene resulted in a warmer and drier climate with longer ice-free periods in the summer and enhanced evaporation of lake water. The reduction in insolation and colder temperatures during the late Holocene caused a reduction in evaporation of lake water over the last 4.1 ka and was accompanied by periodic increases in surface runoff, which correspond with intervals of cold Greenland Ice Sheet surface temperatures.
机译：格陵兰的全新世古气候记录有助于我们了解格陵兰冰原以及区域海洋和大气环流系统对自然气候变化的响应，以便将近期的变化放在长期的视野中。在这里，对格陵兰岛东南部一个湖泊沉积物核心的生物地球化学分析被用来确定全新世期间格陵兰冰盖边缘附近流域的水分平衡和径流变化。从Ammassalik岛的Flower Valley湖中回收了一个1.6 m的沉积岩心，跨越了最后8.8 ka。磁化率，硅藻，整体生物地球化学性质（TOC，C / N，δ〜（13）C_（org））和脂质生物标志物（正构烷烃； C_（16）-C_（31））揭示了碎屑沉积的变化以及陆生和水生有机物的相对输入。中（n-C_（25））和长链（n-C_（29），n-C_（31））正构烷烃的氢同位素值（δD）可重建降水的δD和夏季湖泊的蒸发水。在经历了从8.4 ka到7.0 ka的冰消融化之后的一段早期湖泊发育和景观稳定之后，全新世中期8.4-4.1 ka的特征是湖泊水的蒸发富集程度更高，如δD记录所示。在4.1 ka之后，湖水的蒸发富集减少。磁化率，C / N，δ〜（13）C_（org）和长链正构烷烃浓度的急剧增加也标志着突然向更多变化的沉积转变，表明了陆生有机质的周期性输送和碎屑沉积物到湖中。全新世中期的日照增加导致气候温暖干燥，夏季无冰期更长，湖水蒸发增加。全新世晚期的日照减少和温度降低导致过去4.1 ka的湖水蒸发减少，并伴随着地表径流的周期性增加，这对应于格陵兰冰原表面温度的间隔。

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