Interannual solar and net radiation trends in the Canadian Arctic

Abstract

Net and solar radiation trends over the past half‐century at Alert and Resolute Bay, Nunavut, are presented and analyzed. Substantive changes to the Canadian Arctic climate are observed over the data record. Decreases of 2.25% and 2.50% per decade in solar radiation are observed at Alert and Resolute Bay, respectively. An exploration of cloudless‐day radiation data suggests that this trend is likely driven by changes in atmospheric constituents. Even more significant overall increases in net radiation of 26.7% and 17.9% of the overall mean value per decade are measured at the respective locations, with those changes concentrated in the months of May and June. Exploration of annual and interannual albedo data reflects this result in earlier snowmelt dates and longer snow‐free periods. Evidence is presented showing that, in addition to increased temperatures, changes to the snowmelt date are being driven by increases in winter incoming longwave radiation. Resulting increased totals of net longwave radiation provide enhanced energy for snowmelt, thereby decreasing annual average albedo and increasing annual totals of net radiation. A persistently positive phase of the Arctic Oscillation in the mid‐1990s countered this overall trend and resulted in lower net radiation values. In this period, decreased stratospheric temperatures from an enhanced polar vortex drove decreased snowmelt and lower annual totals of net radiation.