Trends in coastal Arctic fog and its influence on the surface energy balance of glaciers

Breakup of sea ice causes advection and steam fog, which can be persistent over oceans and coasts but diminishes inland. Arctic warming has increased summer sea ice decline and open water exposure, affecting heat and moisture fluxes and therefore cloud formation. Cloudiness has generally increased over the Arctic, but trends differ with cloud vertical distribution as well as seasonally and spatially, with disparate patterns over broken sea ice, open ocean and land. The few studies that separate fog from other clouds report a slight increase in sea fog and slight decrease in land fog over the past decades, but regional and pan-Arctic patterns are equivocal. No studies have focussed on the coast-to-inland transition zone, where many ice sheet outlets and glaciers terminate and where it is suggested that fog and related temperature inversions suppress glacier melt.

In this study, we investigate whether melt season fog frequency and timing has changed in coastal regions around the Greenland Sea over the past 50-70 years. Fog occurrence and characteristics were analysed using synoptic weather data from East Greenland, Jan Mayen, Svalbard and Iceland national and research stations, supplemented with Integrated Global Radiosonde Archive and International Arctic Buoy Programme data. A multivariate fog detection model was developed on the basis weather stations with direct (visibility) and indirect (temperature, relative humidity, wind) fog data. This fog detection model was then applied to stations without direct fog observations, after which daily to seasonal trends in peak frequencies, total fog occurrence, and spatiotemporal patterns could be analysed for all Greenland Sea coastal regions. Occurrence of Arctic sea fog coincides with the glacier ablation season and peaks in July/August. Using fog layer height and fog properties from radiosonde data we calculated fog penetration onto glaciers and determined effects on the radiation budget.