Alkenes in the Arctic boundary layer at Alert, Nunavut, Canada

Measurements of ethene and other non-methane hydrocarbons are reported from intensive measurements campaigns in spring 1998 and 2000. It is argued that the observed levels and the scatter in the data records that have been seen before, are real and not due to canister or other sampling related artifacts. It is then shown that these observations imply that there are local sources for alkenes in the Arctic. Gradient and flux measurements are reported that suggest that this source is in the snow-pack. The flux of ethene out of the snow-pack is estimated to be of the order of 1×10 7 molecules cm −2 s 1 and may be photochemically induced. While small, it is shown that this rate could explain a significant fraction of the observed ethene levels during a typical O 3 depletion episode at Alert.