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

QUATERNARY SCIENCE REVIEWS

卷:243

Article

Bolland, Alexander¹  Rey, Fabian^1,2,3  Gobet, Erika^2,3  Tinner, Willy^2,3  Heiri, Oliver¹ 

[1] Univ Basel, Dept Environm Sci, Geoecol, Klingelbergstr 27, CH-4056 Basel, Switzerland

[2] Univ Bern, Inst Plant Sci, Altenbergrain 21, CH-3013 Bern, Switzerland

[3] Univ Bern, Oeschger Ctr Climate Change Res, Altenbergrain 21, CH-3013 Bern, Switzerland

关键词: Chironomids;    Palaeoecology;    Palaeolimate;    Temperature;    Lateglacial;    Afforestation;   

DOI  :  10.1016/j.quascirev.2020.106484

来源: Elsevier

【 摘 要 】

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 Burgaschisee, 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/Bolling 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 degrees C, indicates temperatures around 9 degrees 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 degrees C for the period 16,100-15,500 cal. BP. Temperatures continue to increase reaching values around 12 degrees C for the period preceding the Bolling warming, when temperatures rose rapidly to values around 15 degrees C. The early temperature rise to values of 10-12 degrees C prior to the Bolling warming agrees with widespread vegetation changes recently reported for this region based on palaeobotanical analyses, which indicate a shift from herbaceous tundra to shrub tundra with low density tree birch stands with open canopies. Together, these results suggest an earlier Lateglacial temperature increase in southwest Central Europe than expected based on earlier palaeobotanical reconstructions, although with a less pronounced warming than has been reported for ca. 16,000 cal. BP from south of the Alps. This early Lateglacial warming agrees with glacier reconstructions which suggest several step-wise reductions of glacier extent in this period as well as with evidence from other palaeotemperature reconstructions and suggests that not only Southern Europe but significant parts of Europe north of the Alps may have been characterized by early Lateglacial warming well before the rapid warming at ca. 14,700 cal. BP. (C) 2020 The Author(s). Published by Elsevier Ltd.

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