Diatom-inferred climatic and environmental changes over the last ∼ 9000 years from a low Arctic (Nunavut, Canada) tundra lake
Diatom-inferred climatic and environmental changes over the last ∼ 9000 years from a low Arctic (Nunavut, Canada) tundra lake
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DOI：
10.1016/j.palaeo.2010.02.030
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发表时间：
2010-05
期刊：
影响因子：
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通讯作者：
C. Paul;K. Rühland;J. Smol
中科院分区：
文献类型：
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作者：
C. Paul;K. Rühland;J. Smol
硅藻组合的变化，全新世从一个14 C测年的沉积物从湖TK-2，一个小的低北极湖位于约。加拿大努纳武特大陆森林-冻原交错带以北200公里处。硅藻组合的显着变化记录在整个核心，这表明在这个地区的全新世时代的环境和气候动态。最早的硅藻组合（CA。9000 cal yr BP）的主要类群是非典型的冰后期组合通常记录在整个北极，并可能表明，全新世早期的条件在湖TK-2相对温暖。一个小的，底栖的，机会主义的脆杆藻类群的优势地位的转变随后（后约。8550口径年BP），更典型的北极组合在最初的湖泊个体发育，这表明发病的凉爽，更碱性的条件。硅藻在约1000年至约2000年之间突然而短暂的显著减少。8550和8500卡。年BP，以及物理和化学指标的相应变化（例如，沉积速率、硅质含量、有机质含量（%）为8.2K冷却异常提供了潜在的证据，这是加拿大北部其他古湖泊学研究中很少认识到的事件。继CA。7000卡2000年BP，一个实质性的转变发生了一个更复杂和多样的硅藻组合，现在包括更多的嗜酸类群。这种成分的变化可能是一个自然的，长期的湖泊碱度损失的指示，并标志着全新世热最大值的开始，这与该地区的温暖时期的时间一致。相对稳定的硅藻组合组成在新冰期期间被打断的关键物种的波动可能与所谓的中世纪温暖期和小冰期。在最近的沉积物中，工业后的小，admittonic小环藻stelligera复杂的扩张，并在重硅化Aulacoseira lirata复杂的同时下降，是类似的变化，越来越多地被认为是地理上广泛的硅藻对最近的气候变暖的反应。湖TK-2硅藻记录提供了重要的见解全新世环境历史的这一未充分研究的加拿大北极地区。此外，它是极少数可能表达8.2K冷事件的北极湖泊之一。
Diatom assemblage changes over the Holocene were examined from a14C-dated sediment core retrieved from Lake TK-2, a small low Arctic lake located ca. 200km north of the forest–tundra ecotone in mainland Nunavut, Canada. Notable changes in the diatom assemblages were recorded throughout the core, suggesting that the Holocene epoch in this region has been environmentally and climatically dynamic. The earliest diatom assemblages (ca. 9000cal yr BP) were dominated by taxa that are atypical of post-glacial assemblages commonly recorded throughout the Arctic, and may suggest that early Holocene conditions at Lake TK-2 were relatively warmer. A shift to dominance by small, benthic, opportunistic Fragilaria taxa followed (after ca. 8550cal. yr BP), more typical of Arctic assemblages during initial lake ontogeny, suggesting the onset of cooler, more alkaline conditions. An abrupt and short-lived marked decrease in diatoms between ca. 8550 and 8500cal. yr BP, with corresponding changes in physical and chemical indicators (e.g., sedimentation rate, siliciclastic content, % organic matter content), provides potential evidence for the 8.2k cooling anomaly, an event rarely recognized from other paleolimnological studies in the Canadian north. Following ca. 7000cal. yr BP, a substantial shift occurred to a more complex and diverse diatom assemblage that now included more acidophilic taxa. This compositional change is likely indicative of a natural, long-term loss of alkalinity in the lake, and marks the onset of the Holocene Thermal Maximum, consistent with the timing of this warm period for this region. The relatively stable diatom assemblage composition during the Neoglacial period was punctuated by fluctuations in key species potentially correlative with the so-called Medieval Warm Period and Little Ice Age. In the most recent sediments, the post-industrial expansion of the small, planktonic Cyclotella stelligera complex, and a concurrent decline in the heavily-silicified Aulacoseira lirata complex, are similar to shifts that are increasingly being recognized as geographically widespread diatom responses to recent climate warming. The Lake TK-2 diatom record provides important insights into the Holocene environmental history of this understudied region of the Canadian Arctic. Furthermore, it is one of the few Arctic lakes in which the 8.2k cold event is possibly expressed.