Characteristics and growth of a snowdrift in arctic Alaska, USA

In arctic Alaska, 15% of the total winter snowpack is contained in large dr ifts. Stratigraphic sections reveal that these can form during as few as fi ve weather events during winter, while comparison of stratigraphy and weath er records show that significant deposition (up to 43% of the total drift v olume) can occur during a single event of short duration (< 72 h). Based on three years of wind, snowfall, and snow transport records, a set of rules was developed for predicting when periods of drift growth would occur. The rules were: 10-m wind speed >5.3 m s(-1) for at least 3 It, wind direction within 30 degrees of the normal to drift trap axis, and recent snowfall ava ilable for transport. When used, these rules successfully identified all dr ift-growth events, plus a few "extra" events that did not contribute substa ntially to drift growth. The extra events were invariably periods when ther e was sufficient wind to move snow, but insufficient snow for transport. In arctic Alaska drift size currently appears to be limited by precipitation rather than wind, leading us to speculate that an increase in precipitation could increase drift size and intensify the ecological, hydrological, and climatic impact of drifts on this arctic system.