The Mountain Legacy Project is a Canadian interdisciplinary undertaking which uses archival research, repeat photography, and scientific, historical, and cultural analysis of repeated historical survey photographs and maps taken in the 1880s to the 1950s by the Geological Survey of Canada and the Department of the Interior’s Dominion Land Survey. This research allows the project to asses how the Canadian Rocky Mountains have changed over the last century. Mountain ranges have a significant impact on the weather, and therefore historical images of these mountains allow researchers to better understand past weather in western North America.
The National Snow and Ice Data Centre uses repeat photography of glacier photographs or “glacier pairs” so that scientists can compare the changes in glaciers over time. This kind of work is aided by the visual appeal of glaciers. Not only researchers and glaciologists, but also casual tourists, often photographed glaciers from similar sites and within conventional frames. The uniformity in how Euro-Americans viewed glaciers is essential to using multiple images through time to understand historical environmental change. The historical photographs date from the late 19th century and early 20th century, and can provide visual evidence of past weather and climates.
The Canadian Ice Service, part of Environment Canada, has ice data from Canadian waters spanning the past four decades. Much of this data has been organised into 30-year ice atlases for three key regions: Northern Canadian Waters (including the Eastern Arctic, Western Arctic and Hudson Bay); the East Coast (Atlantic Canada) and the Great Lakes (including Lake Michigan). The Great Lakes material is also available from the National Oceanic and Atmospheric Administration’s Great Lakes Environmental Research Laboratory. On the Environment Canada website, the atlases are available for each of these regions for both the c.1970-2000 period and for the c. 1980-2010 period. Other associated data and materials related to the recent history of lake and sea ice can be found on this valuable web resource. Most notably, there is a fully searchable online database with weekly ice and iceberg charts since 1999 in their Archive.
The National Air Photo Library, located in Ottawa, was established in 1925 by the Royal Canadian Air Force as the central repository for all aerial photographs over Canadian territory. To view the original photographs you need to either visit the Library or order reproductions. Nevertheless, the NAPL website includes an invaluable map-based search tool that allows you to locate photographs of interest. The search engine returns a listing of aerial photographs flown over a particular area, dates the lines were flown, all the necessary access information, as well as details on the season the photographs were taken and the scale of the photographs.
Aerial photographs can be challenging to work with as lines are rarely flown for the exact dates of interest to a historian. Likewise, they are often focused in on very small areas, there is no guarantee that the exact same line was flown more than once, and the different scale or poor quality of different photos can preclude close study. Nevertheless, comparing aerial photographs flown in different periods of time can clearly show changes in the land, including changes associated with climate such as the extent of permanent snow banks, ice and vegetation cover. You should certainly search online first, to ascertain whether there are images for the time and place of interest, before heading to Ottawa to look at photos.