Late-glacial chironomid-based temperature reconstructions for Lago Piccolo di Avigliana in the southwestern Alps (Italy)

Abstract

Chironomid headcapsules were used to reconstruct late glacial and early-Holocene summer temperatures at Lago Piccolo di Avigliana (LPA). Two training sets (northern Sweden, North America) were used to infer temperatures. The reconstructed patterns of temperature change agreed well with the GRIP and NGRIP δ 18 O records. Inferred temperatures were high during the Bølling (ca 19°C), slowly decreased to ca 17.5°C during the Allerød, reached lowest temperatures (ca 16°C) during the Younger Dryas, and increased to ca. 18.5°C during the Preboreal. The amplitudes of change at climate transitions (i.e. Oldest Dryas/Bølling: 3°C, Allerød/Younger Dryas: 1.5°C, and Younger Dryas/Preboreal: 2.5°C) were smaller than in the northern Alps but similar to those recorded at another site in northeastern Italy. Our results suggest that (1) Allerød temperatures were higher in the southern Alps and (2) higher during the Preboreal (1°C) than during the Allerød. These differences might provide an explanation for the different responses of terrestrial-vegetation to late glacial and early-Holocene climatic changes in the two regions. Other sites on both sides of the Alps should be studied to confirm these two hypotheses.

Terrestrial climate variability and seasonality changes in the Mediterranean region between 15 000 and 4000 years BP deduced from marine pollen records

“…The middle phase of the Younger Dryas, based on the MAT reconstruction, between 12.4 to 12.2 kyr BP shows an temperature increase of 3-5 • C when compared to the colder phases. This pattern is in agreement with GRIP and NGRIP ice-core records (Björck et al, 1998;Rasmussen et al, 2006), pollen-based reconstructions from the Jura and the Balkans (Bordon et al, 2009), and chironomid-based reconstructions from North Italy (Larocque and Finsinger, 2008).…”

“…The quantitative paleoclimatic reconstructions inferred from pollen and chironomids records (e.g. Huntley et al, 1999;Davis et al, 2003;Heiri et al, 2007;Kotthoff et al, 2008a, b;Larocque and Finsinger, 2008), along with model simulations (e.g. Wiersma and Renssen, 2006;Brewer et al, 2007b) also indicate complex climate trends and regional climate patterns across the Mediterranean region for the last 15 000 years BP.…”

Climate warming and vegetation response after Heinrich event 1 (16 700–16 000 cal yr BP) in Europe south of the Alps

“…The general course of temperature at Origlio during the Bølling/Allerød interstadial agrees with other chironomid-based temperature reconstructions from Italy and the Alps (Heiri and Millet, 2005;Heiri et al, 2007b;Larocque and Finsinger, 2008;Ilyashuk et al, 2009;Larocque-Tobler, 2010;Samartin et al, 2012). However, in contrast to the Greenland NGRIP δ 18 O record (Svensson et al, 2008), which shows a gradual declining temperature trend since the onset of the Bølling-Allerød interstadial, the Origlio record, as well as other European chironomidinferred temperature records (e.g.…”

“…A temperature increase in the range of 2-4 • C at the onset of the Bølling-Allerød interstadial was also recorded in chironomid records from northern Italy (Heiri et al, 2007b;Larocque and Finsinger, 2008), the Jura Mountains (Heiri and Millet, 2005), and the Northern Alps (Larocque-Tobler, 2010;Lotter et al, 2012). Wagner-Cremer and Lotter (2011) reconstructed for Schleinsee, southern Germany, an increase from 600 to 700 growing degree-days.…”

“…Reconstructed Bølling/Allerød temperatures are significantly cooler at Origlio than at other sites in northern Italy (Heiri et al, 2007b;Larocque and Finsinger, 2008), if corrected for altitude using standard lapse rates (14 • C vs. ca. 18.5-19.6 • C).…”