Seasonal differences in surface energy exchange and accumulation at Summit, Greenland

The 1997-98 Summit (Greenland) winter-over experiment was conducted to investigate the seasonal changes that might affect snow-air transfer processes and snow chemistry for polar ice-core interpretation. This paper discusses meteorological measurements that were obtained during the experiment. We use the measurements in energy-balance modeling to investigate seasonal differences in the snow-air energy exchange, and to investigate the timing of snow accumulation. We found that the surface energy exchange has distinct seasonal differences. The winter (November-February) has both the coldest average temperatures of the year and the largest temperature variations. The winter also has both the largest peak wind speeds and the longest periods of sustained high winds, Most of the water-vapor transport across the snow-air interface occurs in the summer; indicating that summer may be the primary season for near-surface snow metamorphism. Snow-depth sounder results indicate that snowfall occurs throughout the year at Summit, and thus that the ice-core record may not be affected by large seasonal gaps in the precipitation if accumulation patterns have not changed. The changes in air temperature, wind speed and radiation cause clear seasonal differences in the surface energy balance and snow-surface characteristics that are likely to cause seasonal changes in air-snow transfer processes and snow chemistry as well.