Reconstruction of Summer Temperature for a Canadian High Arctic Site from Retrospective Analysis of the Dwarf Shrub, Cassiope tetragona

Abstract

We used retrospective analysis of the widespread evergreen dwarf-shrub, Cassiope tetragona, to reconstruct average summer air temperature for Alexandra Fiord, Ellesmere Island, Canada. Retrospective analysis is a technique based on dendrochronological methods. In this study, chronologies are based on the morphological characteristics of the plant stems. Two growth and two reproduction chronologies, ranging from 80 to 118 years long, were developed from each of two populations at the High Arctic site. We used multiple regression models to develop a 100-year-long (1895–1994) reconstruction of July–September average air temperature that explained 45% of the climatic variance in the instrumental record. The reconstruction revealed an increase in summer temperature from ∼1905 to the early 1960s, a cooling trend from the mid-1960 to the 1970s, and an increase in temperature after 1980. These historical temperature patterns correspond well with those from other climate proxies from sites on Ellesmere and Devon Islands. As well, the similarity between our model and an arctic-wide proxy temperature time series suggests that the Cassiope-based reconstruction contains a large-scale temperature signal. There is great potential for the development of proxy climate data using Cassiope tetragona from sites throughout the Arctic.