Characteristics, Development, Year-to-Year Variability,
and Environmental Impact of a Large Arctic Alaska Snowdrift
Matthew Sturm1, Glen E. Liston2, and Jon Holmgren1
Arctic tundra snow cover comprises two diametrical components called the veneer and drift facies.
Veneer facies is thin (<0.7 m), wind-blown, and consists of alternating layers of wind slab and depth
hoar. Drift facies is denser, thicker (often in excess of 2 m), and generally consists entirely of wind
slabs. It forms in the lee of bluffs, in gullies, or downwind of isolated shrub stands. Though occupy-
ing less than 5% of the landscape, it plays an important role in the hydrologic cycle because it
continues to release meltwater long after the veneer facies is gone in the spring.
The volume, profile, and basal temperature of a typical large drift located in the foothills north of the
Brooks Range, Alaska, was measured 25 times since 1985, with multiple measurements made during
the winters of 1989 to 1993. Comparison of these measurements to total winter precipitation and
wind speed show a complicated relationship, with both maximum and minimum drift sizes occurring
during years of near-normal precipitation and wind. The results suggest that the largest drifts form
when infrequent optimal conditions (significant snowfall immediately followed by strong wind)
occur. Stratigraphic cross sections through the drift show that 90% of the total drift volume is often
found in fewer than 4 layers of snow (i.e., fewer than 4 transport events). Continuous wind and snow
surface elevation measurements obtained during the winters of 1994, 1995, and 1996 confirm that an
appreciable thickening of the drift takes place only during a few events.
Observations and simulations using a melt model confirm that drifts can persist up to 50 days longer
than the veneer snow. Meltwater derived from the drifts nourish snow bank and small riparian vege-
tation communities. Observations indicate that the under-snow temperatures beneath drifts are ele-
vated, and suggest that migration of groundwater takes place long after the active layer is frozen in
other locations. These factors, in addition to prolonged release of meltwater, may contribute to favor-
ing the growth of these plant communities.
Both the poor correlation between drift size and winter precipitation, and the limited stratigraphic
layering support the hypothesis that the timing of winter wind storms with respect to recent precipi-
tation is the most important factor in drift formation. This finding suggests that prediction of the
hydrologic response of the Arctic to changing climate must include consideration of changes in wind
as well as precipitation, plus their combined timing.
U.S. Army Cold Regions Research and Engineering Laboratory-Alaska, P.O. Box 35170, Fort Wainwright,
Alaska 99703-0170, USA
2 Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado 80523-1371, USA