Evaluating long‐term regional climate variability in the maritime region of the St. Lawrence North Shore (eastern Canada) using a multi‐site comparison of peat‐based paleohydrological records

Abstract

This study presents paleohydrological reconstructions from ombrotrophic peatlands (bogs) along the north shore of the Estuary and the Gulf of St. Lawrence in eastern Canada. Past water table depths were reconstructed based on testate amoebae analyses within four peatlands from two maritime ecoclimatic regions (boreal and subarctic) using a new transfer function. The comparison of multiple peat-based paleohydrological records was used to distinguish climate-driven changes from variations related to site-specific factors. Coherence between the water table reconstructions at the regional scale suggests a common climatic influence on bog paleohydrology but there are inconsistencies which also suggest an influence of non-climatic factors (e.g. internal peatland processes and feedbacks). The surface drying and increased hydrological variability after 3000 cal a BP in the studied bogs coincide with the transition from the Holocene Climatic Optimum to the Neoglacial cooling documented by proxy climate records in eastern Canada. The bogs of Havre St-Pierre have experienced major drying during the late Holocene, indicating important annual-to-centennial water deficits at the peatland surface. Regional differences in the magnitude of the hydrological fluctuations may result from distinctive climatic conditions or could indicate that bog surface wetness in the Gulf of St. Lawrence was more sensitive to past climate changes.

Geochemical characterization (REE, Nd and Pb isotopes) of atmospheric mineral dust deposited in two maritime peat bogs from the St. Lawrence North Shore (eastern Canada)

“…(a) Nd isotope composition, evolution of REE‐dust flux (blue; Pratte et al ., ) for Baie bog; (b) synthesis of water table depth (WTD) reconstructions for the North Shore region (Magnan and Garneau, ); (c) mean annual precipitation (MAP; dashed line) and mean July temperature anomalies (JTA; full line) in northern Quebec (Viau and Gajewski, ); (d) precipitation–temperature residuals of z ‐scores (van Bellen et al ., ); (e) Nd isotope composition, evolution of REE‐dust flux (green; Pratte et al ., ) for IDH bog. Red dashed lines represent Baie samples with REE patterns closer to local soils (see ‘Baie events’; Fig.…”

“…). In the region, greater hydroclimatic variability and drier surface conditions potentially linked to longer seasonal freezing were reported after 3000 cal a BP (Magnan and Garneau, ). Exotic pollen, sea ice and sea surface reconstructions from Newfoundland (Fig.…”

“…Reconstructed WTD on the continental shore suggests wetter and colder conditions on the coast (Fig. 6b; Magnan and Garneau, 2014). Furthermore, Viau and Gajewski (2009) report that northern Quebec was the coldest Canadian region during the Little Ice Age (LIA).…”

“…3). A water table depth (WTD) record from a core collected 5 km north of IDH bog (Plaine bog) displays large hydrological variations over the same period (Magnan and Garneau, 2014), which are not reflected in any proxy from IDH bog. The geographical setting (on an island, protected by a forest fringe, higher elevation) of the IDH bog was invoked as a factor reducing the amount of dust being deposited on the site and explaining the low dust flux (Pratte et al, 2017).…”

A 9600‐year record of water table depth, vegetation and fire inferred from a raised peat bog, Prince Edward Island, Canadian Maritimes

“…Charman et al ., ; Väliranta et al , ; Lamentowicz et al ., ; Amesbury et al ., ; Väliranta et al , ), North America (e.g. Loisel and Garneau, ; Lamarre et al ., ; Magnan and Garneau, ) and South America (e.g. Loisel and Yu, ; Mauquoy et al ., ; Van Bellen et al ., ).…”