Interannual trends in the radiation climatology of the Canadian high Arctic

Net and solar radiation trends over the past half-century at Alert and Resolute, Nunavut are presented and analyzed. Substantive changes to the Canadian Arctic climate are observed over the data record. A significant decrease in solar radiation is observed at both sites. An even more significant overall increase in net radiation is measured, with those changes concentrated in the months of May and June. Exploration of annual and interannual albedo trends and cluster analysis of natural seasons both reflect this result in earlier snowmelt dates and longer snow-free periods. A persistently positive phase of the Arctic Oscillation in the mid 1990's countered this overall trend and resulted in lower net radiation values. Evidence is presented showing that in addition to increased temperatures, changes in the winter longwave radiation regime have driven the observed net radiation trends.