Summer temperature development 18,000-14,000 cal. BP recorded by a new chironomid record from Burgäschisee, Swiss Plateau

• Published in: Quaternary Science Reviews
• Main Authors: Bolland, Alexander, Rey, Fabian, Gobet, Erika, Tinner, Willy, Heiri, Oliver
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier 2020
• Subjects: Norway; glacier; North Atlantic
• Online Access: https://edoc.unibas.ch/77918/; https://doi.org/10.1016/j.quascirev.2020.106484

The termination of the Last Ice Age after the Last Glacial maximum (LGM) represents a dynamic period in the history of the circum-north Atlantic region. So far, there are few reliably dated climatic reconstructions covering the Lateglacial period prior to 14,700 cal. BP in Central and Northern Europe. We present a new chironomid record for the period 18,000-14,000 cal. BP, from Burgäschisee, Switzerland. Chironomid assemblages immediately following glacier retreat were dominated by taxa indicative of cold, oligotrophic conditions such as Sergentia coracina -type and Micropsectra radialis -type. A gradual transition to assemblages with moderate abundances of taxa indicative of warmer climatic conditions such as Dicrotendipes nevosus -type and Tanytarsus glabrescens -type started after ca. 16,100 cal. BP. This initial and gradual chironomid assemblage shift culminated in a more pronounced and rapid inferred temperature change at the Oldest Dryas/Bølling transition at ca. 14,700 cal. BP, where further types indicative of warm conditions such as Tanytarsus lactescens -type first occurred and replaced chironomids indicative of colder conditions such as Paracladius and Protanypus . We estimated past July air temperature changes from the chironomid assemblages by applying to the record a chironomid-temperature transfer function that is based on chironomid distribution data from 274 lakes in Switzerland and Norway. The resulting reconstruction, which features a sample-specific root mean square error of prediction of 1.36-1.46 °C, indicates temperatures around 9 °C at the beginning of the record. An initial gradual warming phase initiating at ca. 16,100 cal. BP is recorded reaching values around 10 °C for the period 16,100-15,500 cal. BP. Temperatures continue to increase reaching values around 12 °C for the period preceding the Bølling warming, when temperatures rose rapidly to values around 15 °C. The early temperature rise to values of 10-12 °C prior to the Bølling warming agrees with widespread vegetation changes ...