Dark Snow, the dust factor and the 2014 melt season onset

A new study[1] finds that the snow albedo feedback by snow grain growth alone is insufficient to explain the observed decrease in the springtime Greenland ice sheet reflectivity. They propose a theory that “recent warming in the Arctic has induced an earlier disappearance of the seasonal snow cover, uncovering large areas of bare soil and thus enhancing dust erosion”. The vigorous late winter wind would take the dust to Greenland.

Year 2014 Greenland upper elevations ice reflectivity has been at record low values much of 2014 so far, and in recent years, consistent with the conclusions of Dumont et al. (2014). See the blue line; year 2014.

2500-3200m_Greenland_Ice_Sheet_Reflectivity

Year 2014 Greenland upper elevations ice reflectivity has been at record low values much of 2014 so far, consistent with the conclusions of Dumont et al. (2014) for recent years. See the blue line (year 2014) in March.

2014 is on track for a big melt year at the upper elevations. What could shut this down would be heavy snowfall there. For the ice sheet as a whole, 2014 reflectivity has been trending near the low side of past observations since 2000. Is this the early spring dust factor? More springtime dust certainly is a factor. What will determine how much punch the 2014 melt season delivers depends a lot on temperatures and atmospheric circulation in the month of June. Here we go.

0-3200m_Greenland_Ice_Sheet_Reflectivity

What’s been driving the low reflectivity anomaly for the ice sheet the past 10 days is melting concentrated along the southeast ice sheet. Note the red areas below.

Alb_LA_EN_20140606

Greenland ice albedo anomaly we are posting at polarportal.dk. Note the red, orange and yellow areas along the southeast ice sheet. The melt story so far for June is the southeast. It’s been since 2006 that this was the high melt story.

I’m today on my way to Greenland, to the western ice sheet, to camp there in the blue area of the map where there appears to be above average snow depth, contributing to the positive reflectivity anomaly. We may well have to put the camp in at a lower elevation where melt is more advanced because this extra half meter of melting snow, a.k.a. slush would be most unpleasant to camp in/on. Wish us luck.

Works Cited

  1. Dumont, M., E. Brun, G. Picard, M. Michou, Q. Libois, J-R. Petit, M. Geyer, S. Morin and B. Josse, Contribution of light-absorbing impurities in snow to Greenland’s darkening since 2009, Nature Geoscience, 8 June, 2014, DOI: 10.1038/NGEO2180

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