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Dansgaard-Oeschger cycles and Heinrich events in western Europe - A diatom perspective
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
Responsible organisation
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The last glacial period was characterised by several abrupt climatic shifts referred to as Dansgaard-Oeschger (DO) cycles and Heinrich events. These shifts were most frequent between 60,000 and 20,000 years before present coinciding with Marine Isotope Stages (MIS) 3 and 2. DO cycles and Heinrich events have been most thoroughly investigated in marine and ice core records while their impact on terrestrial environments is less well known. The high-resolution, multi-proxy investigation of a long sediment sequence, obtained from the former lake at Les Echets in France, aims at filling this gap and allows determining the impact of these climatic events on the lake and its catchment. The site and its surroundings experienced distinct shifts in lake organic productivity and catchment conditions as a consequence of DO climate variability and Heinrich events. The detailed analysis of the fossil diatom record shows distinct changes in diatom productivity, diversity and community composition, which are most likely due to variations in the length of lake ice cover, thermal stratification regimes and catchment conditions during a DO cycle. The distinct reduction in lake organic productivity and particularly low concentrations of diatom valves during intervals corresponding to Heinrich events suggest that these cold and arid phases had the most severe impact on the paleolake at Les Echets. The results of this thesis provide new insight into the impact of abrupt climate change on lacustrine ecosystems and show the potential of high-resolution and multi-proxy studies in paleoenvironmental research.

Place, publisher, year, edition, pages
Stockholm: Institutionen för naturgeografi och kvartärgeologi , 2008.
Series
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 16
Keyword [en]
Dansgaard-Oescher cycles, Heinrich events, MIS 3 and 2, diatoms, Les Echets, France
National Category
Geology
Research subject
Quarternary Geology
Identifiers
URN: urn:nbn:se:su:diva-8259ISBN: 978-91-7155-758-2 (print)OAI: oai:DiVA.org:su-8259DiVA: diva2:199925
Public defence
2008-11-14, William-Olssonsalen, Geovetenskapens hus, Svante Arrhenius väg 8 A, Stockholm, 13:00
Opponent
Supervisors
Available from: 2008-10-23 Created: 2008-10-10Bibliographically approved
List of papers
1. Rapid ecosystem response to abrupt climate changes during the last glacial period in western Europe, 40-16 ka.
Open this publication in new window or tab >>Rapid ecosystem response to abrupt climate changes during the last glacial period in western Europe, 40-16 ka.
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2008 In: Geology, ISSN 0091-7613, Vol. 36, no 5, 407-410 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:su:diva-25537 (URN)000255853300018 ()
Note
Part of urn:nbn:se:su:diva-8259Available from: 2008-10-23 Created: 2008-10-10Bibliographically approved
2. Paleolimnological response to millennial and centennial scale climate variability during MIS 3 and 2 as suggested by the diatom record in Les Echets, France
Open this publication in new window or tab >>Paleolimnological response to millennial and centennial scale climate variability during MIS 3 and 2 as suggested by the diatom record in Les Echets, France
2008 (English)In: Quaternary Science Reviews, ISSN 0277-3791, Vol. 27, no 15-16, 1493-1504 p.Article in journal (Refereed) Published
Abstract [en]

A 27 m long sediment sequence retrieved from the central part of the Les Echets basin in France has been analysed in sub-centennial resolution for biogenic silica and fossil diatom remains. The sequence corresponds to the later part of Marine Isotope Stage (MIS) 3 and to most of MIS 2. Distinct changes in diatom productivity, diversity and taxonomic composition between 36.2 and 31.7 kyr BP appear to relate to Dansgaard–Oeschger (DO) climate variability. Intervals characterized by low diversity, productivity and small-sized benthic diatom taxa are most likely a response to colder conditions in relation to DO stadials. In contrast, higher diversity, productivity and a high abundance of planktonic taxa indicate a response to warmer temperatures during DO interstadials. The time interval between 30.3 and 15.7 kyr BP is characterized by continuous low diatom productivity and a benthic dominated community with intermediate species richness, suggesting a transition to more stable conditions. Three time intervals with extremely low concentrations of diatom valves (46.1–36.2, 31.7–30.3 and 26.3–23.6 kyr BP) overlap with ages reported for Heinrich (H) events 4, 3, and 2. We speculate that the lake at Les Echets suffered from severe ecological stress as a response to H events. This is the first detailed study exemplifying the response of a lake, based on diatoms, to climate variability during late part of MIS 3 and most of MIS 2 in Europe.

National Category
Geology
Identifiers
urn:nbn:se:su:diva-25538 (URN)10.1016/j.quascirev.2008.04.014 (DOI)000259017900002 ()
Note
Part of urn:nbn:se:su:diva-8259Available from: 2008-10-23 Created: 2008-10-10 Last updated: 2012-02-09Bibliographically approved
3. Diatom community dynamics during abrupt climate change: the response of lacustrine diatoms to Dansgaard-Oeschger cycles during the last glacial period
Open this publication in new window or tab >>Diatom community dynamics during abrupt climate change: the response of lacustrine diatoms to Dansgaard-Oeschger cycles during the last glacial period
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Manuscript (Other academic)
Identifiers
urn:nbn:se:su:diva-25539 (URN)
Note
Part of urn:nbn:se:su:diva-8259Available from: 2008-10-23 Created: 2008-10-10 Last updated: 2010-01-13Bibliographically approved
4. Modest summer temperature variability during DO cycles in western Europe - an answer to a long time paradox?
Open this publication in new window or tab >>Modest summer temperature variability during DO cycles in western Europe - an answer to a long time paradox?
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Manuscript (Other academic)
Identifiers
urn:nbn:se:su:diva-25540 (URN)
Note
Part of urn:nbn:se:su:diva-8259Available from: 2008-10-23 Created: 2008-10-10 Last updated: 2010-01-13Bibliographically approved

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