Thursday, 30 October 2014

Dark Snow

About the August, 2014 dark Greenland photos
Jason Box


29 October, 2014


Photos and video I took during an August 2014 south Greenland maintenance tour of promice.org climate stations and an extreme ice survey time lapse camera went viral, featuring a surprisingly (to me and others) dark surface of Greenland ice.
Photo by Jason Box
Photo by Jason Box
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What we know, the southern Greenland ice sheet hit record low reflectivity in the period of satellite observations since 2000 due to a ~2 month drought affecting south Greenland….

nland…
2014_August_record_map
map with colors indicating when record low albedo was observed. The photos are from the blue patch near the southern tip of Greenland.
Snowfall summer 2014  for south Greenland would have kept the melt rates down by brightening up the surface. Summer 2014, at the PROMICE.org QAS_A site, we recorded ice loss from the surface at a place we thought was above equilibrium line altitude, where the surface would lose no ice in an ‘average climate’. The higher than normal melt rates allowed the impurities to concentrate near the surface in a process documented for snow surfaces by Doherty et al. (2013).

To avoid misinterpretation, black carbon is only part of the darkness, the rest is dust and microbes (See Dumont et al. 2014 and Benning et al. 2014). The photos are from the lowest part of the ice sheet’s elevation. The upper elevations do not get nearly this dark. This satellite image illustrates for west Greenland how dark the surface gets, down to 30% reflectivity.

Work Cited
  • Benning, L.G. A.M. Anesio, S. Lutz & M. Tranter, Biological impact on Greenland’s albedo, Nature Geoscience 7, 691 (2014) doi:10.1038/ngeo2260
  • Doherty, S. J., T. C. Grenfell, S. Forsstro¨ m, D. L. Hegg, R. E. Brandt, and S. G. Warren (2013), Observed vertical redistribution of black carbon and other insoluble light-absorbing particles in melting snow, J. Geophys. Res. Atmos., 118, 5553–5569, doi:10.1002/jgrd.50235.
  • 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



Photo by Jason Box
Photos by Jason Box

For the website Dark Snow GO HERE





This lecture is from January, 2013


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