Outcomes (wp2)

 Through questionnaires and a study with local resident participants, we showed that snow cover can affect light exposure, alertness and melatonin suppression in residents. Indoor dwellers at Northern latitudes struggle to obtain adequate natural light exposure to sustain mood and alertness during December and January. However, snow cover increases morning light exposure, lowers melatonin levels, and enhances alertness and activity throughout the day. On the other hand, snow cover had minimal influence on sleep-wake cycles, sleep quality, and daytime mood ratings. With increasing distance to winter solstice, mood, alertness and melatonin regained levels observed during summer periods. Our results indicate that in winter, snow cover plays a crucial role in strengthening the human diurnal rhythm by increasing light exposure and activity levels. By climate change, snow depth has declined. It is likely that further reductions in snow cover can have significant implications for northern latitudes.