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Late Holocene high precipitation events recorded in lake sediments and catchment geomorphology, Lake Vuoksjávrátje, NW Sweden
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
Stockholm University, Faculty of Science, Department of Geological Sciences.
CNRS, EcoLab, Castanet Tolosan, France.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

In this paper, we highlight the importance of combining multi-proxy analysis of lake sediments with associated catchment geomorphology to better understand the late Holocene palaeoenvironmental evolution in a high latitude Alpine lake in N Sweden. Previous studies have suggested that such lakes may be highly sensitive to variations in catchment erosion and variations in precipitation, and that this sensitivity may influence ecologically-based reconstructions of past temperature changes. Here we have analysed lake sediments covering the last 5100 years from Lake Vuoksjávrátje in NW Sweden to identify different erosional regimes in the lake catchment and to identify sediment sources and lake sedimentary processes, which ultimately affect the palaeoecological record. Methods that were used include XRF core scanning, grain size analysis and geomorphological mapping, supported by previously published chironomid, total organic carbon and carbon/nitrogen data. From the integrated results we identify time intervals when increased amounts/intensity of precipitation altered sedimentation and lake catchment erosional processes. The most prominent event in our record occurred between 3090 and 2750 cal. a BP and is interpreted to be the result of excessive precipitation in relation to the 2.8 ka event. By combining the multi-proxy analysis of a lake sediment core with a detailed catchment characterisation it is possible to reach a better understanding of the processes active within the lake catchment, the factors governing the erosional regimes and the way these are recorded in lake sediments. For future palaeoclimatological research based on lake sediments we recommend increasing the integration of catchment geomorphology, sedimentology and palaeoecology.

Keyword [en]
Holocene, Precipitation, Catchment erosion, Solifluction, Lake sediments, Geomorphology, XRF core scanning, Grain size
National Category
Geology
Research subject
Quaternary Geology
Identifiers
URN: urn:nbn:se:su:diva-107071OAI: oai:DiVA.org:su-107071DiVA: diva2:743052
Available from: 2014-09-03 Created: 2014-09-03 Last updated: 2014-09-05
In thesis
1. The sensitivity of Swedish alpine lakes to hydro-climatic changes during the Late Holocene
Open this publication in new window or tab >>The sensitivity of Swedish alpine lakes to hydro-climatic changes during the Late Holocene
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The thesis objective is to use lake sediments to investigate the relationships between chironomids, as proxy for temperature, and δ18O and minerogenic in-wash, as precipitation proxies, in northern Sweden during the Late Holocene. Three lakes along a N–S transect in the Scandes were studied using biological, geochemical and physical sediment properties, together with numerical methods. Emphasis was put on changes in hydrological and erosional regimes and the configurations of lake catchments in an attempt to avoid misinterpretation of the climate signals. Mean July air temperatures were inferred from the chironomid composition in sediment records covering the last 5000 yrs in Vindelfjällen Mountains in Mid Lapland and the last 1000 yrs in Jämtland. The temperature reconstructions underwent significance tests, suggesting reliable results for the Vindelfjällen reconstruction but not the Jämtland reconstruction. Data from XRF core scanning and grain size variations, interpreted together with catchment geomorphology, suggested periods with increased fluvial erosion. A major flood event occurred at the Vindelfjällen site c. 2800 cal. yr BP. Furthermore, this record indicates stream flow and wetland surface erosion during the last 1200 yrs. Seasonal variations in the amount of precipitation, reflecting changes in atmospheric circulation during the last 1000 yrs, were reconstructed based on δ18O in diatoms from one lake in Jämtland and one in northern Lapland. Relatively higher summer precipitation was inferred between AD 1000 and 1080, AD 1300 and 1440, and during the early 19th century as a result of a positive Arctic Oscillation mode. Changes in chironomid composition in the Jämtland lake were concurrent with shifts in δ18Odiatom suggesting indirect responses to circulation changes. Changes in precipitation are suggested to be an important factor that may cause the spatially variable results among chironomid-based July air temperature reconstructions in Scandinavia.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography and Quaternary Geology, Stockholm University, 2014. 34 p.
Series
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 44
Keyword
alpine lake sediments, temperature reconstruction, precipitation, catchment erosion, chironomids, oxygen isotopes, XRF core scanning, geomorphology, grain size analysis
National Category
Geology
Research subject
Quaternary Geology
Identifiers
urn:nbn:se:su:diva-107073 (URN)978-91-7447-978-2 (ISBN)
Public defence
2014-10-09, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)
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Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

Available from: 2014-09-18 Created: 2014-09-03 Last updated: 2014-10-30Bibliographically approved

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