Document generated on 09/25/2021 5:12 a.m. Géographie physique et Quaternaire The Paleoecological Record of 6 ka BP Climate in the Canadian Prairie Provinces Données paléoécologiques sur le climat des provinces des Prairies à 6 ka BP Palaoökologische Belege über das Klima in den kanadischen Prärie-Provinzen um 6 ka v.u.Z. Robert E. Vance, Alwynne B. Beaudoin and Brian H. Luckman La paléogéographie et la paléoécologie d’il y a 6000 ans BP au Canada Article abstract Paleogeography and Paleoecology of 6000 yr BP in Canada Synthesis of available paleoecological studies in the Prairie provinces of Volume 49, Number 1, 1995 Canada indicates that although the peak in postglacial aridity that characterized early Holocene climate of the western foothills and plains had URI: https://id.erudit.org/iderudit/033031ar passed, conditions remained warmer and drier than present throughout the DOI: https://doi.org/10.7202/033031ar region ca. 6000 yr BP Compared to today, treeline elevations were higher and alpine glaciers were reduced in size in the Rocky Mountains, lake levels were lower over much of the Interior Plains, and the grassland and boreal forest See table of contents ecozones extended north of their present positions. Forest fires were more prevalent ca. 6000 yr BP than they are today, aiding westward migration of jack pine (Pinus banksiana) through the boreal forest and increasing the area Publisher(s) occupied by grassland in boreal and montane forest regions. Attempts to quantify the magnitude of 6 ka temperature and precipitation differences have Les Presses de l'Université de Montréal produced variable results, but suggest that mean annual temperature was 0.50°C to 1.50°C higher than today (summer temperature may have been up to ISSN 3°C higher) and mean annual precipitation was reduced by 65 mm (or summer 0705-7199 (print) precipitation was reduced by 50 mm), compared to present. The nature and 1492-143X (digital) scale of these changes suggests that a vigorous zonal atmospheric circulation pattern, similar to that of the 1930s but shifted northward, prevailed at 6 ka. Explore this journal Cite this article Vance, R. E., Beaudoin, A. B. & Luckman, B. H. (1995). The Paleoecological Record of 6 ka BP Climate in the Canadian Prairie Provinces. Géographie physique et Quaternaire, 49(1), 81–98. https://doi.org/10.7202/033031ar Tous droits réservés © Les Presses de l'Université de Montréal, 1995 This document is protected by copyright law. Use of the services of Érudit (including reproduction) is subject to its terms and conditions, which can be viewed online. https://apropos.erudit.org/en/users/policy-on-use/ This article is disseminated and preserved by Érudit. Érudit is a non-profit inter-university consortium of the Université de Montréal, Université Laval, and the Université du Québec à Montréal. Its mission is to promote and disseminate research. https://www.erudit.org/en/ Géographie physique et Quaternaire, 1995, vol. 49, n° 1, p. 81-98, 8 fig., 1 tabl.. THE PALEOECOLOGICAL RECORD OF 6 KA BP CLIMATE IN THE CANADIAN PRAIRIE PROVINCES* Robert E. VANCE, Alwynne B. BEAUDOIN and Brian H. LUCKMAN, respectively: Geological Survey of Canada, 3303- 3310St. NW, Calgary, Alberta T2L 2A7; Archaeological Survey, Provincial Museum of Alberta, 12845-102nd Ave., Edmon­ ton, Alberta T5N 0M6; Department of Geography, University of Western Ontario, London, Ontario N6A 5C2. ABSTRACT Synthesis of available RÉSUMÉ Données paléoécologiques sur ZUSAMMENFASSUNG Palaoôkologische paleoecological studies in the prairie prov­ le climat des provinces des prairies à 6 ka. Belege ùber das Klima in den kanadischen inces of Canada indicates that although the BP La synthèse des études paléoécologi­ Prârie-Provinzen um 6 ka v.u.Z. Die peak in postglacial aridity that character­ ques montrent qu'à 6 ka le maximum d'ari­ Synthèse der verfùgbaren palâoôkolo- ized early Holocene climate of the western dité, qui caractérisait l'Holocène inférieur, gischen Studien in den Prârie-Provinzen foothills and plains had passed, conditions avait été atteint, mais le climat demeurait Kanadas zeigt, daf3 das Klima in der ganzen remained warmer and drier than present plus chaud et plus sec que maintenant dans Region um etwa 6000 Jahre v.u.Z. warmer throughout the region ca. 6000 yr BR Com­ toute la région. Les différentes limites des und trockener als gegenwârtig blieb, wenn pared to today, treeline elevations were arbres étaient plus élevées qu'aujourd'hui auch das Maximum an postglazialer higher and alpine glaciers were reduced in et la superficie des glaciers alpins étaient Trockenheit, welches im frùhen Holozàn das size in the Rocky Mountains, lake levels plus petite, les niveaux lacustres étaient Klima der westlichen Gebirgsauslâufer und were lower over much of the Interior Plains, moins élevés dans la plus grande partie Ebenen charakterisierte, vorùber war. and the grassland and boreal forest des plaines intérieures et les écozones des Verglichen mit heute waren die Baum- ecozones extended north of their present prairies et de la forêt boréale s'étendaient grenzen hôher und die alpinen Gletscher in positions. Forest fires were more prevalent plus au nord qu'aujourd'hui. Les feux de den Rocky Mountains kleiner, die Seehôhen ca. 6000 yr BP than they are today, aiding forêt étaient plus fréquents à 6 ka qu'ac­ waren niedriger im grôBten Teil der inneren westward migration of jack pine (Pinus tuellement, ce qui a favorisé la migration du Ebenen, und die Ôkozonen von Grasland banksiana) through the boreal forest and pin gris (Pinus banksiana) vers l'ouest à und nôrdlichem WaId erstreckten sich weiter increasing the area occupied by grassland travers la forêt boréale et accru la superfi­ nôrdlich als heute. Waldbrânde traten um in boreal and montane forest regions. At­ cie de la prairie dans les zones de forêts etwa 6000 v.u.Z. hâufiger als gegenwârtig tempts to quantify the magnitude of 6 ka boréale et alpine. Les essais faits dans le auf und haben so die Westwàrtswanderung temperature and precipitation differences but de mesurer l'ampleur des différences von Graukiefer (Pinus banksiana) durch den have produced variable results, but sug­ de températures et de précipitations à 6 ka nôrdlichen WaId begùnstigt und die gest that mean annual temperature was ont donné des résultats variables, mais Graslandflàchen in den Gebieten des 0.50C to 1.50C higher than today (summer montrent que la température était de 0,5 à nôrdlichen und alpinen Waldes vergrôBert. temperature may have been up to 3°C 1,5°C plus élevé que maintenant (avec une Versuche, den Umfang der Unterschiede in higher) and mean annual precipitation was température estivale jusqu'à 3°C plus éle­ Temperatur und Niederschlàgen um 6 ka reduced by 65 mm (or summer precipita­ vée) et les précipitations annuelles moyen­ zu bestimmen, ergaben wechselnde tion was reduced by 50 mm), compared to nes étaient de 65 mm inférieures (avec des Ergebnissse, doch zeigen sie, daB die present. The nature and scale of these précipitations estivales de 50 mm inférieu­ durchschnittliche jâhrliche Temperatur 0.5° changes suggests that a vigorous zonal res) à maintenant. La nature et le degré C bis 1.50C hôher als gegenwârtig war (die atmospheric circulation pattern, similar to des changements laissent croire qu'une Sommertemperatur dûrfte bis zu 3°C hôher that of the 1930s but shifted northward, pre­ forte circulation atmosphérique zonale, sem­ gewesen sein) und die durchschnittlichen vailed at 6 ka. blable à celle des années 1930, mais plus jâhrlichen Niederschlâge waren um 65 mm nordique, existait à 6 ka. geringer (oder die Sommer-Niederschlàge waren um 50 mm geringer) verglichen mit heute. Die Natur und der Grad dieser Wechsel lassen vermuten, daB eine krâftige zonale atmosphàrische Strômung, àhnlich der von den 1930 iger Jahren aber nôrdlicher gelagert, um 6 ka vorherrschte. Manuscrit reçu le 10 juin 1994; manuscrit révisé accepté le 7 novembre 1994 * Geological Survey of Canada Contribution No. 52193 82 R.E. VANCE, A.B. BEAUDOIN and B.H. LUCKMAN INTRODUCTION less landscape of gently undulating grassland. In fact, the three prairie provinces embody a great deal of geomorphic, Shifts in the position of regional vegetation belts and climatic, and ecological variability. Large scale physiographic changes to regional surface hydrology are among the clear­ features, shaped by Cretaceous and Tertiary bedrock, form est indicators of past climate change. Over the last twenty- a series of prairie 'steps' across the southern half of the five years, an extensive network of paleoecological study three provinces (Klassen, 1989). The easternmost step, the sites focused on these topics has been developed in Mani­ Manitoba Escarpment, separates the Manitoba Plain (ca. toba, Saskatchewan, and Alberta; a network of sufficient 250 m asl) from the Saskatchewan Plain (ca. 400-800 m scope to allow a preliminary assessment of paleoclimatic asl) which, in turn, is separated from the Alberta Plain (ca. conditions across the Canadian Prairies. A number of 800-1000 m asl) by the Missouri Coteau. The Alberta Plain paleoclimatic indices may be consulted to reconstruct cli­ grades into the eastern slope foothills of the Rocky Moun­ matic conditions ca. 6000 yr BP, including several pollen tains which rise steeply to the continental divide at ca. stratigraphie studies from all ecological zones, investigation 3000 m asl) In the northwest, the Alberta Plateau (ca. 600- of high altitude glacier and treeline dynamics in the Rocky 900 m asl) is dissected by the Peace River Lowland (ca. Mountains, as well as a number of diverse paleolimnological 300-600 m asl). The northeastern portion of the prairie studies. The purpose of this synthesis is to describe, both provinces is part of the Precambrian Shield, whose surface qualitatively and quantitatively, how climatic conditions 6000 expression consists of extensive poorly drained, low relief years ago differed from those of today.