89th American Meteorological Society Annual Meeting

Monday, 12 January 2009
Ice-core evidence of a pyrocumulonimbus wildfire in 1950
Hall 5 (Phoenix Convention Center)
Robert Field, Univ. of Toronto, Toronto, ON, Canada; and G. W. K. Moore, G. Holdsworth, and C. Tymstra
We provide evidence that a 1950 NO3- spike in the Mt. Logan ice core is attributable to a single wildfire in western Canada, which caused the “Great Smoke Pall” event of September 1950. During this event, smoke from a large forest fire in western Canada caused night-time conditions during the day in major Canadian and US cities, before being transported to Europe. Using atmospheric trajectory analysis, we show that the smoke observations in the lower troposphere over North America are best explained by smoke injection below 5km. Upper tropospheric observations of the plume made by aircraft over the UK, however, are best explained by injection heights near or above the tropopause. From Europe, these high-altitude trajectories continued around the northern hemisphere, reaching the west coast of North America several weeks later, including the Mt. Logan region. To the best of our knowledge, this would be the earliest documented instance of pyrocumulonimbus injection of wildfire smoke into the stratosphere, circumpolar smoke transport, and of a single wildfire detected in an ice core.

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