Here's a link to Jason Box 2012 analysis of albedo over the Greenland ice sheet. The reduction of the albedo is a critical factor for enhancing melting over the Greenland ice sheet. The image on the left shows the ice sheet albedo time series updated through July 2012 by Jason Box. 

To better understand the importance of this mechanism you can check a recently published paper on the Cryosphere Discussion by Box et al. (2012) in which we focus on this problem or another paper (Tedesco et al., 2011) that we published on Environmental Research Letters focusing on the role of albedo and accumulation on the 2010 melting recording in Greenland. Both papers are also available in the Scientific Literature section of this site. 

Year 2011 Greenland melting remains well above the (1979 – 2010) average; close-to-record mass loss

Melting in Greenland in 2011 was still above the average (1979 – 2010 baseline period), exceptionally high over the west coast and reaching close-to-record simulated surface mass balance, bare ice exposure, albedo and runoff anomalies. See here for more details or go to http://greenland2011.cryocity.org