It has been a very late spring across most of Alaska, but
Barrow is right on time. Snowmelt is just starting to kick in. Today was warm,
36 - 38 F and quite windy, up to 25mph for most of the day. The top few inches
of snow are already ripe, that is liquid water on the snow crystals. The whole
snowpack is isothermal at 0°C, but the whole snowpack must be saturated with
liquid water before we start worrying about runoff. There is no water at the
base of the snowpack yet, so runoff is certainly not imminent. If the weather
continues like this, it could be soon. But coastal Alaska usually bounces back
and forth between warm and cold for several weeks before the snow finally
disappears. Snowmelt on the Coastal Plain is typically a long slow process, but
the snowpack is pretty thin, so I suspect it will be a short fast melt, if it
stays warm. Yesterday it was almost 100% snow cover, but the number of bare
spots really increased throughout the day today. Our measurements have shown
the snowpack has about 3.5” to 5.1” (about 8 or 9 cm) of water equivalent. That
means if all the snow suddenly melted, we’d have a layer water about 4 inches
deep, which isn’t very much water when one considers this is the total winter
accumulation. We don’t get mid-winter melts here. Some of the snow does
sublimate but most accumulates all winter to melt in a brief spring. Summer
rainfall is quite low, so this snowmelt is the major source of water to
replenish lakes, streams and depleted soil moisture.
Hiroki Ikawa and I have come up to get ready for snowmelt. This
is the biggest hydrologic event of the year in the Arctic, well maybe the
biggest biological and cultural event too. Winter ends quickly and everything
goes from frozen to wet. We have been repeating extensive measurements of the
snowpack every day. The difference from one day to the next tells us how much
snow has melted. This is very useful information for calibrating hydrological and
thermal models. It takes over half the day to complete the snow surveys. We have
an efficient process, but it is still a big job. After we finish the snow
surveys, we have been removing the snow from several of the polygon troughs. We
want to document the direction the water is flowing, again for calibration of
hydrological models. The terrain here is so flat, a snow drift can influence
the direction of flow. We want to determine
how the terrain controls runoff, so we must eliminate any snow damming. It is a
big job. Although the snow is not deep, we need to dig a long distance in this
flat area to avoid backing up from a snow dam.
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| Post-doctoral fellow Hiroki Ikawa is repeating snow surveys every day to document the rate of snow melt. We are still able to use snow machines now, so we are trying to pre-position supplies and equipment in the field. When the snow cover is gone, we must protect the fragile tundra surface, so all access to the field will again be on foot. |
The Coastal Plain will be an amazing place in a few weeks. Migratory
birds that spent the winter in more temperate climes will be back for their
annual reunion. It is always spectacular. The numbers and sizes of the flocks
are incredible. I hope everyone gets to experience snowmelt in Barrow some
time.
