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Late-Holocene temperature and precipitation changes in Vindelfjallen, mid-western Swedish Lapland, inferred from chironomid and geochemical data
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
2014 (engelsk)Inngår i: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 24, nr 1, s. 78-92Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

In this article, we present results from a palaeolimnological study from Lake Vuoksjavratje in the mountain tundra region in the Vindelfjallen Mountains, northwest Sweden. We suggest that the influence of precipitation may be one of the factors causing discrepancies between chironomid-based late-Holocene July temperature (JulyT) reconstructions from Fennoscandia. We combine quantitative temperature reconstruction using chironomids for the last 5100 years with qualitative analysis of chironomid composition and geochemical analyses, such as x-ray fluorescence (XRF), total organic carbon (TOC) and C/N analysis. The studied sequence is dated by Pb-210, Cs-137 and 11 C-14 datings from terrestrial macrofossils. The aim of the study was to use chironomids to reconstruct late-Holocene summer temperature variation on a multi-centennial to centennial timescale and to use geochemical data to identify periods during which the changes in chironomid composition might have been forced by environmental variables other than temperature, such as within lake processes or precipitation. Based on ordination techniques, and a comparison between chironomid-inferred JulyTs and changes in minerogenic sedimentation with regional temperature and wetness records, it is concluded that the JulyT signal was modulated by precipitation. The proxies indicate that both JulyT and annual precipitation have influenced the chironomid communities in Lake Vuoksjavratje, and that catchment-related processes caused by enhanced precipitation have overridden the summer temperature signal between 3000 and 2200 cal. yr BP, and between 1050 and 100 cal. yr BP.

sted, utgiver, år, opplag, sider
2014. Vol. 24, nr 1, s. 78-92
Emneord [en]
chironomids, late Holocene, northern Sweden, precipitation, temperature reconstruction, x-ray fluorescence
HSV kategori
Identifikatorer
URN: urn:nbn:se:su:diva-99867DOI: 10.1177/0959683613512167ISI: 000328828800007OAI: oai:DiVA.org:su-99867DiVA, id: diva2:690645
Merknad

AuthorCount:3;

Tilgjengelig fra: 2014-01-24 Laget: 2014-01-20 Sist oppdatert: 2018-01-11bibliografisk kontrollert
Inngår i avhandling
1. The sensitivity of Swedish alpine lakes to hydro-climatic changes during the Late Holocene
Åpne denne publikasjonen i ny fane eller vindu >>The sensitivity of Swedish alpine lakes to hydro-climatic changes during the Late Holocene
2014 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
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.

sted, utgiver, år, opplag, sider
Stockholm: Department of Physical Geography and Quaternary Geology, Stockholm University, 2014. s. 34
Serie
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 44
Emneord
alpine lake sediments, temperature reconstruction, precipitation, catchment erosion, chironomids, oxygen isotopes, XRF core scanning, geomorphology, grain size analysis
HSV kategori
Forskningsprogram
kvartärgeologi
Identifikatorer
urn:nbn:se:su:diva-107073 (URN)978-91-7447-978-2 (ISBN)
Disputas
2014-10-09, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (engelsk)
Opponent
Veileder
Merknad

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

Tilgjengelig fra: 2014-09-18 Laget: 2014-09-03 Sist oppdatert: 2014-10-30bibliografisk kontrollert

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