It has been discovered that the size distribution of atmospheric aerosols in air masses over central Alaska varies systematically with air temperature. Cold air masses contain relatively few, coarse aerosols. Aerosols in warm Pacific-marine air masses, on the other hand, are plentiful in number, but their mean size and mass loading is small. There are decreasing numbers of cloud condensation nuclei, but substantial increases in aerosol mass with decreasing temperatures. We speculate that the cause is related to a combination of air pollution transport from Eurasia into the Arctic air mass and photolytic creation of nuclei in the sunlit Northern Pacific. ¿ American Geophysical Union 1988