ABSTRACT: Spatial patterns of Holocene paleoclimatic change in the Canadian Arctic Islands.

CGRG Bibliography of Canadian Geomorphology
Search Results

Author :

Date :

Title :

Publication :

Issue :

Page(s) :

Abstract

A greater understanding of the potential impact of climatic change on terrestrial and freshwater ecosystems can be obtained by observing how climate variability of the past affected Arctic ecosystems. Fossils extracted from lake sediment cores are used to identify long term environmental change and reconstruct past climates. However, few records spanning the Holocene have been produced from the Canadian Arctic, and the spatial patterns of historical climate variability across the region remain poorly known. We present data from a series of lake sediment cores from across the Canadian Arctic Islands to quantify spatial variability in Holocene paleoclimates, and to determine local effects of climatic changes on ecosystems. A multi-proxy approach is used to provide independent paleoclimatic records. Due to the availability of calibration datasets of ecological data, it is now possible to attempt quantitative reconstructions of past temperatures and biological production. Pollen, diatomand chironomid-based paleoclimate reconstructions, as well as high resolution analyses of biogenic silica and sediment properties, are broadly coherent within one site, although there remain some differences between paleoclimate values estimated by the different proxies. Using fossil pollen dataand an extensive modern calibration set, we estimate early Holocene temperatures of 1-2 degrees C higher than the early 20th century across a broad area of the Canadian Arctic; this ŤHolocene Thermal Maximumť occurred about 10000 to 6500 cal yr BP in the western Canadian Arcticat site KR02 on Victoria Island, and at about 9000 cal yr BP in the central Arctic at Lake PW02 on Prince of Wales Island. Elevated biological production across different trophic levels, measured using a combination of biogenic silica, percent organic matter and the concentrations of microfossils, is also noted at that time at many sites. Neoglacial cooling is observed in many records after 4000 cal yr BP; the transition to cooler climates is often associated with declines in diatom production, and a rise in diatom diversity. Millennial-scale climate variability is identified in both terrestrial and freshwater fossil sequences. For the past millennium, these changes are broadly coherent across several cores, with some spatial variability both in terms of timing and magnitude across the Archipelago. Nonanalogue conditions, that is, communities in the past which do not resemble any observed today in the Arctic, have been identified, as has been found in temperate regions, but it isstill unclear if this is due to insufficient calibration data or true non-analogue conditions. Although significant progress has been made in mapping Holocene paleoclimates across this region, more progress is needed on modern calibration of the proxies, taxonomic harmonization, obtaining betterchronologies and increasing the density of sites available for reconstructions.

Bibliography of Canadian Geomorphology