In the news yesterday NASA reported that 97% of the surface area of the Greenland Ice Sheet was experiencing melt according to satellite data. Normally the highest central parts of the ice sheet do not experience any surface melting.

The image was taken from the NASA website where a full press statement is also available:

http://science.nasa.gov/science-news/science-at-nasa/2012/24jul_greenland/

Interestingly, melt events at the highest location on Greenland from which an ice core has been taken show melt events occurring about every 150 years according to Lora Koenig, a Goddard glaciologist, so although its very unusual and unprecedented in the satellite era it is not unprecedented in the ice core records.

Field scientists have confirmed slightly positive air temperatures for a few hours, and the majority of the meltwater produced at the highest elevations will presumably refreeze rapidly almost in situ, but it will be interesting to see if that affects the evolution of the albedo of the ice sheet in the coming weeks, and if an impact from the large melting area can be detected in measurements of ice flow velocity in outlet glaciers nearer the margins. An interesting case study for the Greenland scientists.