Early August 2012 Greenland ice reflectivity dips again below 2 standard deviations
by Jason Box, Melt Factor blog, August 6, 2012
As in the mid-July case, the early August ice sheet albedo has declined to an average more than 5% (or 2 standard deviations) below the average of the previous 12 years (2000-2011). A “2-sigma” event has a probability of occurrence under 5% in a random climate.
The decline is again concentrated in the accumulation area above 1,500-m elevation where melting is less common as it is in the lower elevations.
The thermodynamic impact of widespread reflectivity decline is:
- more ice sheet solar energy absorption
- more erosion of snowpack heat content
- more preconditioning of future early melt onset cases
- more melting in 2012
The early August decline is similar to August declines in 2008, 2004, and 2001. What is different is that the decline is from a lower point.
The August 4, 2012, albedo is not as low as the lowpoint reached on July 15, 2012.
- Box, J. E., Fettweis, X., Stroeve, J. C., Tedesco, M., Hall, D. K., and Steffen, K.: Greenland ice sheet albedo feedback: thermodynamics and atmospheric drivers, The Cryosphere, 6, 821-839; doi:10.5194/tc-6-821-2012, 2012. open access