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The sensitivity of ...
The sensitivity of Swedish alpine lakes to hydro-climatic changes during the Late Holocene
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- Berntsson, Annika, 1979- (författare)
- Stockholms universitet,Institutionen för naturgeografi och kvartärgeologi (INK)
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- Rosqvist, Gunhild, professor (preses)
- Stockholms universitet,Institutionen för naturgeografi och kvartärgeologi (INK)
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- Langdon, Peter G., Dr. (opponent)
- University of Southampton
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(creator_code:org_t)
- ISBN 9789174479782
- Stockholm : Department of Physical Geography and Quaternary Geology, Stockholm University, 2014
- Engelska 34 s.
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Serie: Dissertations from the Department of Physical Geography and Quaternary Geology, 1653-7211 ; 44
- Relaterad länk:
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https://urn.kb.se/re...
Abstract
Ämnesord
Stäng
- 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.
Ämnesord
- NATURVETENSKAP -- Geovetenskap och miljövetenskap -- Geologi (hsv//swe)
- NATURAL SCIENCES -- Earth and Related Environmental Sciences -- Geology (hsv//eng)
Nyckelord
- alpine lake sediments
- temperature reconstruction
- precipitation
- catchment erosion
- chironomids
- oxygen isotopes
- XRF core scanning
- geomorphology
- grain size analysis
- kvartärgeologi
- Quaternary Geology
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