The NASA MODIS sensor on the Terra satellite provides surface reflectivity data since early 2000 enabling us to evaluate just how dark Greenland ice is today and in comparison with the past 14 years.
The data show that 2014 ice sheet reflectivity (also called albedo) has been near record low much of 2014, especially at the highest elevations.
The darkness of the surface at high elevations is consistent with the findings of Dumont et al. (2014) that an increasing dust concentration on the ice sheet in the pre-melt season from decreasing snow cover on land upwind of the ice sheet may be a significant darkening factor.
If there will be a persistent pattern of warm air brought over the ice sheet as in 2012, we should expect melting at the ice sheet upper elevations. Why? Low reflectivity heats the snow more than normal, removing more of the ‘cold content’. A dark snow cover will thus melt earlier and more intensely. A positive feedback exists for snow in which once melting begins, the surface gets yet darker due to increased liquid water content, increased snow grain size, and possible other factors such as microbial growth.
For the ice sheet as a whole, low reflectivity in 2014 has been exceeded only by years 2012, 2013, and 2011, depending on the time of year…
The Greenland reflectivity anomaly map features red and orange colors that indicate a relatively dark surface near the end of June especially at the low elevations where most melting occurs.
- 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