ARCUS | Arctic Research Consortium of the United States

7th Annual ARCUS Award for Arctic Research Excellence


Submitted by   Shelly Rayback
Authors   Shelly A. Rayback and G. H. R. Henry
Category   Interdisciplinary Research
Title   Recontructing Twentieth Century Summer Temperature in the Canadian High Arctic from Retrospective Growth Analysis of Cassiope tetragona
Affiliation   Department of Geography, University of British Columbia, Vancouver, BC, Canada

Abstract

In order to understand the current and future impact of climate change in the Arctic, it is important to develop proxy records to obtain an empirical description of past climate variability including its modes of behavior, its extremes and the duration of trends and cycles. With proxy climate records, a more confident estimation can be made of the roles of different external forcing factors and internal sources of variability on past and recent climate. Using retrospective techniques on the circumpolar, evergreen, dwarf shrub, Cassiope tetragona, summer temperature was reconstructed for a Canadian High Arctic site on Ellesmere Island. The retrospective analysis technique used in this study was based upon the principles of dendrochronology and the later modification of this technique by Johnstone and Henry where establishing the patterns of the positioning of the leaf node scars along the plant stem can extend chronologies by 10 to 15 years. By developing C. tetragona chronologies of 100 years or longer, a better understanding of the temporal variability of climate over the last century might be achieved. This is particularly important given the range of environmental conditions the Arctic has experienced since the end of the Little Ice Age (ca. 1850). In addition, because C. tetragona is a circumpolar species and can be found as a dominant or co-dominant plant in multiple tundra ecosystems, it may be used to generate proxy climate data from a dense network of terrestrial sites across the circumpolar north. The potential for increasing the number of proxy data sets using C. tetragona would contribute greatly to our understanding of spatial variability of climate in the Canadian High Arctic. The 95-year long reconstruction of average air temperature explains 51% of the dependent climatic variance. This study's reconstruction clearly shows an increase in summer temperature from the 1920s to the 1960s, a cooling period during the 1960s and 1970s, and finally, the current period of warming in the Canadian Arctic, which began in the 1980s. Evidence from other proxy records in the Canadian Arctic support this study's conclusions.