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North Atlantic region atmospheric circulation dynamics inferred from a late-Holocene lacustrine carbonate isotope record, northern Swedish Lapland
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
2007 (English)In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 17, no 7, 867–873- p.Article in journal (Refereed) Published
Abstract [en]

The first high-resolution record of climate variation based on the oxygen and carbon isotope composition of authigenic carbonate for northern Scandinavia is presented. Modern lake-water isotope data indicate that controls on its oxygen and hydrogen (δ18O<sub>w</sub> and δD<sub>w</sub>) composition are unlikely to be evaporation or temperature, and its variations must therefore reflect changes in, or at the source of, precipitation. Substantial and persistent changes of the isotopic composition of the precipitation are required to change the mean annual isotope composition of lake surface water. For this reason we argue that the recorded changes were significant and that the recurrence of such changes would greatly affect future regional climate conditions in the North Atlantic region. Oxygen isotope (δ<sup>18</sup>O) minima occurring at ~ 200, 500, 1300, 1600 and at 2900 cal. yr BP all coincide with major peaks in North Atlantic ice rafted debris deposition. We suggest that the depletion events in δ<sup>18</sup>O cycles recorded in several lakes in northern Swedish Lapland are caused by the same climatic shifts as those noted in the North Atlantic marine records. This is because changes of atmospheric circulation pattern and the lower ocean and atmospheric temperatures associated with the IRD events help to explain why 18O depletion of precipitation occurred during these events. Our findings indicate that the recorded changes in North Atlantic ice drift and surface hydrography are coupled to changes in atmospheric circulation. 

Place, publisher, year, edition, pages
2007. Vol. 17, no 7, 867–873- p.
Keyword [en]
Oxygen isotopes, carbonate lake sediments, atmospheric circulation dynamics, North Atlantic IRD, late Holocene, northern Sweden
Identifiers
URN: urn:nbn:se:su:diva-20556ISI: 000251541400001OAI: oai:DiVA.org:su-20556DiVA: diva2:187082
Available from: 2008-01-09 Created: 2008-01-09 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Holocene climate and atmospheric circulation changes in northern Fennoscandia: Interpretations from lacustrine oxygen isotope records
Open this publication in new window or tab >>Holocene climate and atmospheric circulation changes in northern Fennoscandia: Interpretations from lacustrine oxygen isotope records
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis investigates how variations in the oxygen isotopic composition of lake waters in northern Fennoscandia are recorded in lake sediment archives, especially diatoms, and how these variations can be used to infer past changes in climate and atmospheric circulation. Results from analyses of the oxygen isotopic composition of lake water samples (δ18Olakew) collected between 2001 and 2006 show that δ18O of northern Fennoscandian lakes is mainly controlled by the isotopic composition of the precipitation (δ18Op). Changes in local δ18Op depend on variations in ambient air temperature and changes in atmospheric circulation that lead to changes in moisture source, vapour transport efficiency, or winter to summer precipitation distribution. This study demonstrates that the amount of isotopic variation in lake water δ18O is determined by a combination of the original δ18Olakew, the amount and timing of the snowmelt, the amount of seasonally specific precipitation and groundwater, any evaporation effects, and lake water residence time. The fact that the same isotope shifts have been detected in various δ18Olakew proxies, derived from hydrologically different lakes, suggests that these records reflect regional atmospheric circulation changes. The results indicate that diatom biogenic silica isotope (δ18Odiatom) records can provide important information about changes in atmospheric circulation that can help explain temperature and precipitation changes during the Holocene. The reconstructed long-term Holocene decreasing δ18Op trend was likely forced by a shift from strong zonal westerly airflow (relatively high δ18Op) in the early Holocene to a more meridional flow pattern (relatively low δ18Op). The large δ18Olakew depletion recorded in the δ18O records around ca. 500 cal yr BP (AD 1450) may be due to a shift to more intense meridional airflow over northern Fennoscandia resulting in an increasing proportion of winter precipitation from the north or southeast. This climate shift probably marks the onset of the so-called Little Ice Age in this region.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography and Quaternary Geology, Stockholm University, 2009. 30 p.
Series
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 18
Keyword
oxygen isotope, diatom silica, lake sediment, atmospheric circulation, North Atlantic Oscillation, northern Fennoscandia, The Holocene, Little Ice Age
National Category
Physical Geography
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-29343 (URN)978-91-7155-904-3 (ISBN)
Public defence
2009-10-02, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: In press. Paper 2: Submitted. Paper 5: In progress.Available from: 2009-09-10 Created: 2009-08-24 Last updated: 2010-04-22Bibliographically approved

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