Evidence for cooler European summers during periods of changing meltwater flux to the North Atlantic

Heiri, Oliver and Tinner, Willy and Lotter, André F.. (2004) Evidence for cooler European summers during periods of changing meltwater flux to the North Atlantic. Proceedings of the National Academy of Sciences of the United States of America, 101 (43). pp. 15285-15288.

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Official URL: https://edoc.unibas.ch/67700/

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We analyzed fossil chironomids (nonbiting midges) and pollen in two lake-sediment records to reconstruct and quantify Holocene summer-temperature fluctuations in the European Alps. Chironomid and pollen records indicate five centennial-scale cooling episodes during the early- and mid-Holocene. The strongest temperature declines of approximate to1degreesC are inferred at approximate to10,700-10,500 and 8,2007,600 calibrated C-14 years B.P., whereas other temperature fluctuations are of smaller amplitude. Two forcing mechanisms have been presented recently to explain centennial-scale climate variability in Europe during the early- and mid-Holocene, both involving changes in Atlantic thermohaline circulation. In the first mechanism, changes in meltwater flux from the North American continent to the North Atlantic are responsible for changes in the Atlantic thermohaline circulation, thereby affecting circum-Atlantic climate. In the second mechanism, solar variability is the cause of Holocene climatic fluctuations, possibly triggering changes in Atlantic thermolhaline overturning. Within their dating uncertainty, the two major cooling periods in the European Alps are coeval with substantial changes in the routing of North American freshwater runoff to the North Atlantic, whereas quantitatively, our climatic reconstructions show a poor agreement with available records of past solar activity. Thus, our results suggest that, during the early- and mid-Holocene, freshwater-induced Atlantic circulation changes had stronger influence on Alpine summer temperatures than solar variability and that Holocene thermolhaline circulation reductions have led to summer-temperature declines of up to 1degreesC in central Europe.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Geowissenschaften > Geoökologie (Heiri)
UniBasel Contributors:Heiri, Oliver
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:National Academy of Sciences
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:30 Nov 2020 12:53
Deposited On:30 Nov 2020 12:53

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