Surface Climate and SnowWeather Relationships of the Kuparuk Basin
29
ing in a different sequence can produce a wide range of snowpack characteristics,
and these have a commensurately wide range of impacts on the environment and
man.
Surprisingly, but for the same reasons that the winter climate of the Kuparuk
tends to fall within a narrow range, the sequence of weather events observed
along the Kuparuk River is sufficiently similar from year to year to produce a
similar snowpack. As a consequence, stratigraphic and textural characteristics of
the snow tend to be similar from one year to the next--sometimes strikingly
similar--even though the potential exists for the snow cover to exhibit a much
wider range of characteristics.
Figure 9 shows the snow stratigraphy of the Kuparuk Basin for early and late
winter. The total snow depth and the layer thickness varies considerably, but sev-
eral features repeat from one location to another:
Two to four relatively thick layers of depth hoar are found at the base of
the pack in most places,
The depth hoar is capped by a thick wind slab that is in place by late
November,
Relatively few layers are added between December and April, and
Overall, no more than eight distinct layers comprise the total pack.
These salient characteristics are not unique to the winter of 1996-97. For all
winters for which we have snow pit data (19891997), similar features were
observed. Figure 10 shows the snow cover stratigraphy near the end of the cold
season for the four winters of 19951998. Despite differences in depths and layer
thickness, overall the same characteristics appear.
The snow characteristics are linked directly to the climate and weather
events. Depth hoar is produced when relatively fluffy, low-density snow is sub-
jected to strong temperature gradients for days to weeks (Akitaya 1974, Trabant
and Benson 1972, Sturm 1991). Virtually every winter on the Arctic Slope, this
condition is met. Further, the formation of depth hoar is enhanced because early-
season snowfalls tend to be light and fluffy, falling with little wind (Fig. 6),
though the reason for this low wind regime and associated snowfall is not well
understood. Wind slabs are produced by winds in excess of 4.56 m s1, provided
there is sufficient snow available for transport (Kuz'min 1963). The snow pit
data strongly suggest that the conditions needed to produce these strong winds
tend not to materialize until the end of EC, when much of the season's snow
cover has already been deposited. In the following pages we will examine some
of these characteristics and the recurrent weather events that give rise to them,
and we will explain them where possible.
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