Comparison of quantitative Holocene temperature reconstructions using multiple proxies from a northern boreal lake

Four biotic proxies (plant macrofossils, pollen, chironomids and diatoms) are employed to quantitatively reconstruct variations in mean July air temperatures (Tjul) at Lake Loitsana (northern Finland) during the Holocene. The aim is to evaluate the robustness and biases in these temperature reconstr...

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Bibliographic Details
Published in:Holocene (Sevenoaks) 2017-11, Vol.27 (11), p.1745-1755
Main Authors: Shala, Shyhrete, Helmens, Karin F, Luoto, Tomi P, Salonen, J Sakari, Väliranta, Minna, Weckström, Jan
Format: Article
Language:English
Subjects:
Air temperature
Aquatic ecosystems
chironomids
Climate
Delayed response
Diatoms
ecological drivers
Fossil assemblages
Fossils
Holocene
Lake sediments
Lakes
northern boreal Fennoscandia
plant macrofossils
Pollen
Sediments
Terrestrial environments
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Summary:Four biotic proxies (plant macrofossils, pollen, chironomids and diatoms) are employed to quantitatively reconstruct variations in mean July air temperatures (Tjul) at Lake Loitsana (northern Finland) during the Holocene. The aim is to evaluate the robustness and biases in these temperature reconstructions and to compare the timing of highest Tjul in the individual reconstructions. The reconstructed Tjul values are evaluated in relation to local-scale/site-specific processes associated with the Holocene lake development at Loitsana as these factors have been shown to significantly influence the fossil assemblages found in the Lake Loitsana sediments. While pollen-based temperatures follow the classical trend of gradually increasing early-Holocene Tjul with a mid-Holocene maximum, the aquatic/wetland assemblages reconstruct higher-than-present Tjul already during the early Holocene, that is, at the peak of summer insolation. The relatively low early-Holocene July temperatures recorded by the pollen are the result of site-specific factors possibly combined with a delayed response of the terrestrial ecosystem compared with the aquatic ecosystem. Our study shows that all reconstructions are influenced at least to some extent by local factors. This finding stresses the need to evaluate quantitatively reconstructed climate values against local lake development and highlights the benefit of using multi-proxy data in Holocene climate reconstructions.
ISSN:0959-6836
1477-0911
1477-0911
DOI:10.1177/0959683617708442