Wednesday, May 22, 2013
Snowmelt is near, but not quite here…
Spring is slowly finding its way to Barrow. We’ve seen several flocks of ducks and heard some geese. It has been quite warm during the day, but still freezing at night. I saw one duck in a melt pond just outside Barrow. He was paddling like crazy to keep the pond from freezing.
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.
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.