Peatlands to the Rescue! Late Holocene History of Climate and Storms as Told by Coastal Peatlands on the Magdalen Islands, Québec, Canada

• Main Author: Lachance, Antoine
• Format: Thesis
• Language: English
• Published: 2022
• Subjects: Canada; Magdalen; North Atlantic
• Online Access: https://spectrum.library.concordia.ca/id/eprint/991372/; https://spectrum.library.concordia.ca/id/eprint/991372/1/Lachance_MSc_S2023.pdf

Storms are pervasive dangers to coastal communities in Eastern Canada and, under future climate scenarios, these extreme weather events are projected to increase in intensity. However, the impacts of climate change on storm variability have not been studied extensively in this region, in part due to the short and incomplete instrumental storm records. Environmental paleo-data archives recording high-impact storms on multi-centennial to multi-millennial timescales can provide invaluable information to document past storm variabilities and to support and inform adaptation strategies. First, a review of the literature on paleo-storm studies from the North Atlantic was conducted. Then, a reconstruction of late Holocene environmental changes and storms is presented, based on the analyses of two ombrotrophic peat cores from the Magdalen Islands, Québec, in the Gulf of St. Lawrence. The cores were dated by 14C and 210Pb, with the bottommost peat dating to ~4920 BP and ~4720 BP. We used a multi-proxy approach based on sedimentological and geochemical analysis to examine the evolution of the peatlands, as well as local climate on the Magdalen Islands during the past 4000 years, and to reconstruct storms during the past 1000 years, i.e., the period for which both cores display clear ombrotrophic conditions. The storm reconstruction was validated using the hurricane record from the Magdalen Islands over the past 150 years, and shows a particularly active period between 1400-1650 CE, when heightened activity was also identified in other studies from the northwestern North Atlantic, as well as a notable increase in storms since 1930 CE. While warm sea-surface temperature (SST) anomalies seem to have contributed to more frequent storms since 1930 CE, the 1400-1650 CE active period occurred during the Little Ice Age (LIA), a period of generally cooler SSTs in the North Atlantic. Our study is the first to use ombrotrophic peat cores to track storm frequency in eastern North America, as well as one of the northernmost ...