early-August 2012 Greenland ice reflectivity dips again below 2 standard deviations

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 1500 m elevation where melting is less common as it is in the lower elevations.

The thermodynamic impact of widespread reflectivity decline is:

  1. more ice sheet solar energy absorption
  2. more erosion of snowpack heat content
  3. more preconditioning of future early melt onset cases
  4. more melting in 2012

…all in a self-reinforcing feedback loop that amplifies melting (see Box et al. 2012, link below).

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 4 August 2012 albedo is not as low as the lowpoint reached on 15 July, 2012.

Work Cited

  • 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

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