Major postglacial summer temperature changes in the central coniferous boreal forest of Quebec (Canada) inferred using chironomid assemblages

Abstract

Chironomid head capsules preserved in lake sediments were used to reconstruct 8200 years of summer temperatures in the boreal forest of north‐eastern Canada. Two training sets were used derived from Canadian and Eastern Canadian transfer functions. Both models reconstructed similar climate patterns, but the Canadian model provided temperatures generally 2–3 °C lower than the Eastern Canadian model. Three main thermal changes inferred by chironomids were: (i) the Holocene Thermal Maximum, which occurred between 8 and 5k cal a BP, with temperatures generally higher than today's, maximum temperatures between 8 and 6.5k cal a BP, and an average of + 0.9 °C; (ii) the Medieval Climate Anomaly around 1.1–1.2k cal a BP with an amplitude of + 0.7 °C; and (iii) a colder period reconstructed between the 14th and 19th centuries, corresponding to the Little Ice Age, with summer temperatures on average −0.5 °C lower than the climate normal. For each of these three climatic events, the timing and the amplitude of changes were similar with other published regional, North American and Northern Hemisphere records.

A chironomid-inferred Holocene temperature record from a shallow Canadian boreal lake: potentials and pitfalls

“…WAPLS 999-bootstrap with two components yielded a correlation coefficient (r 2 boot) of 0.85, an RMSEP of 1.67˚C and a maximum bias of 3.05˚C. Occurrence of taxa and temperature optima can be found in Bajolle et al (2018) and in Table 2. Sample specific errors (eSEP) were calculated.…”

“…1), where a chironomid-inferred temperature reconstruction was carried out and was similar to regional and hemispheric temperature records (Bajolle et al 2018). Multi-site comparison [Lac Lili versus Lac Aurélie (Bajolle et al 2018)] will place the climate reconstruction within a regional context. If the patterns are similar at both sites, it will provide support for regional climate change having been reconstructed accurately, whereas if they diverge.…”

“…A new Eastern Canadian model, modified from Larocque et al (2006) and Larocque (2008), and utilized for climate reconstruction at Lac Aurélie (Bajolle et al 2018), was used. The training set comprises 75 lakes (no outliers) and 79 taxa with abundances of >1% in more than two lakes.…”

Coniferization of the mixed‐wood boreal forests under warm climate

“…The last 2000 years included both the warm Medieval Climate Anomaly (MCA; approximately 1000 ± 300 cal a BP), and the cold and wet Little Ice Age (LIA; approximately 300 ± 100 cal a BP) (Kerwin et al, 2004;Booth et al, 2006). The MCA was a rapid, intense climate change recorded by several studies in eastern Canada (Bajolle et al, 2018), in Greenland (Kobashi et al, 2010), and more largely in the Northern Hemisphere (PAGES 2k Consortium, 2013;Ljungqvist, 2010), and suspected to have increased the fire activity for a short duration in some boreal forest regions (Kelly et al, 2013;El-Guellab et al, 2015). These more frequent fires were not recorded in our fire reconstructions, but were observed at other sites in north-eastern Canada (Ali et al, 2012;El-Guellab et al, 2015;Remy et al, 2017).…”

“…9000 to 4000 cal a BP), to the cold and moist Neoglacial period (ca. from 4000 cal a BP) (Davis et al, 2000;Viau and Gajewski, 2009;Bajolle et al, 2018). We endeavored to investigate two areas which were close enough in proximity to be subject to the same climate conditions and potential vegetation dynamics during the Holocene (Senici et al, 2015(Senici et al, , 2013.…”