Climatic change in central Canada : a preliminary analysis of weather information from the Hudson's Bay Company Forts at York Factory and Churchill Factory, 1714-1850.

Abstract

A reconstruction of climate at the southern end of Hudson Bay has been developed for the period from 1714 to 1852 from diaries, weather journals and instrumental records maintained by employees of the Hudson's Bay Company. In order to cope with a variety of data, that can be generally classified as historical or secular, a coding technique for adaptation to a computer was developed that allowed for the integration of the two distinctly different types of material. Two sites at York Factory and Churchill Factory located approximately 100 miles apart on the southwest shore of Hudson Bay were studied. In this way homogeneity could be checked because changes at one site would be reflected in changes at the other unless they were caused by local variations. The study provides a long term record of climate change in a region that has received very little attention and yet is very significant to the general pattern of climates in the northern hemisphere. Analysis of temperature, wind, precipitation, thunder and lightning, frost, and phenologic events indicate trends similar to those found in other parts of the northern hemisphere, but attempts at comparison of individual years with those experienced in Europe proved fruitless. The weather was more severe than at present in the first half of the 18th Century with colder temperatures, more days with snowfall and a higher percentage of northerly winds. From approximately 1780 to 1815 there appears to have been a great deal of variability in the weather particularly in the number of days with precipitation. A critical change seems to have occurred in 1760. Prior to that date the two sites experienced very similar weather but after that date the variations are similar but the intensities and frequencies of events are quite different. This appears to indicate a change in the mean position of the Arctic Front so that York Factory, which had previously experienced Tundra type weather similar to Churchill Factory, after that date had weather symptomatic of the Boreal forest region