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Abrupt climate change and early lake development – the Lateglacial diatom flora at Hässeldala Port,southeastern Sweden 
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下载免费PDF全文 Linda Ampel Malin E. Kylander Margret Steinthorsdottir Barbara Wohlfarth 《Boreas: An International Journal of Quaternary Research》2015,44(1):94-102
The fossil diatom record from the Hässeldala Port palaeolake, southeastern Sweden, offers an excellent opportunity to investigate how past climatic shifts influenced catchment conditions and early lake development. The record, dating to between 13 900 and 11 200 cal. a BP, covers a climatically dynamic period, starting with deglaciation followed by oscillations between warmer and colder climate states. The stratigraphical changes in the fossil diatom assemblages show a trend of less open‐water taxa and a successively more complex periphytic community as the lake shallows and the aquatic habitat structure develops. A diatom‐based reconstruction of lake water pH indicates a natural acidification trend early in the record from 13 900 to 12 500 cal. a BP. From 12 500 cal. a BP, coincident with the start of climate cooling, to 11 300 cal. a BP this trend is disrupted and lake waters become more alkaline. A cooler and drier climate most likely resulted in reduced soil organic matter build‐up as well as more frozen ground that impeded hydrological flow and decreased the input of dissolved organic matter and organic acids into the lake system. This study demonstrates the importance of the hydrological system as a link between terrestrial and aquatic ecosystems during early lake ontogeny. 相似文献
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Linda Ampel Barbara Wohlfarth Jan Risberg Daniel Veres Melanie J. Leng Päivi Kaislahti Tillman 《Journal of Paleolimnology》2010,44(2):397-404
The sedimentary record from the paleolake at Les Echets in eastern France allowed a reconstruction of the lacustrine response
to several abrupt climate shifts during the last glacial period referred to as Dansgaard–Oeschger (DO) cycles. The high-resolution
diatom stratigraphy has revealed distinct species turnover events and large fluctuations in stable oxygen isotope values in
diatom frustules, as a response to DO climate variability. More or less identical species compositions became re-established
during each DO stadial and interstadial phases, respectively. However, the relative abundance of the most dominant species
within these assemblages varies and might indicate differences in climatic conditions. Interstadial phases are characterized
by identical species successions. Transitions from stadial to interstadial conditions show a distinct Fragilaria–Cyclotella succession, which resembles the diatom regime shifts that have been recognized in some lakes in the Northern Hemisphere since
the mid-nineteenth century. 相似文献
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Maarten Blaauw Barbara Wohlfarth J. Andrés Christen Linda Ampel Daniel Veres Konrad A. Hughen Frank Preusser Anders Svensson 《第四纪科学杂志》2010,25(3):387-394
Several large abrupt climate fluctuations during the last glacial have been recorded in Greenland ice cores and archives from other regions. Often these Dansgaard–Oeschger events are assumed to have been synchronous over wide areas, and then used as tie‐points to link chronologies between the proxy archives. However, it has not yet been tested independently whether or not these events were indeed synchronous over large areas. Here, we compare Dansgaard–Oeschger‐type events in a well‐dated record from southeastern France with those in Greenland ice cores. Instead of assuming simultaneous climate events between both archives, we keep their age models independent. Even these well‐dated archives possess large chronological uncertainties that prevent us from inferring synchronous climate events at decadal to multi‐centennial time scales. If possible, comparisons between proxy archives should be based on independent, non‐tuned time‐scales. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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