Last January Dr. Jason E. Box. research scientist at Byrd Polar Research Center, reported on his Meltfactor blog that the Greenland ice sheet was getting less and less reflective. Albedo, the reflecting power of a surface that is defined as the ratio of reflected radiation, is high when the ice sheet is covered with white snow. But as temps go up this snow starts to get darker, more of the surface below gets uncovered and a vicious cycle starts: more snow melts, snow gets dirtier, reflects less solar energy, more melt, etc. Other factors that influence the albedo of the Greenland ice sheet, is total prior snowfall, rain, and snow impurities, such as dust and soot from wildfires and human-produced pollution. The sooner the snow starts to deteriorate in spring/summer, the less reflectivity and thus more melt there will be.
The image above comes from a more recent blog post on Meltfactor: Greenland ice sheet reflectivity at record low, particularly at high elevations. Albedo at lower elevations is lower, because temperatures are higher there and more of the surface below the snow/ice becomes bare.
Dr. Box writes:
Ice sheet reflectivity this year has been the lowest since accurate records began in March, 2000. In this condition, the ice sheet will continue to absorb more solar energy in a self-reinforcing feedback loop that amplifies the effect of warming. It’s not a runaway loop, just an amplifier. A record setting melt season is likely if this pattern keeps up this year.
Perhaps most remarkable about the 2012 pattern is how much darker the snow and ice is becoming, not only at the lowest elevations around the ice sheet periphery where melting is always most intense, but in the higher elevation net snow accumulation area.
Here are graphs showing the albedo since 2000 at different elevations (regularly updated here):
But it's not only visible on graphs or anomaly maps. We can see it with the naked eye as well. Look at these radar images for day 180 (h/t Chris Biscan):
Here I compare satellite images of the area behind Jakobshavn Glacier in southwest Greenland for the last three years (look at that snow line retreating):
Speaking of Jakobshavn Glacier, it appears that there has been more calvings in the past 12 months. Here's a CAD image that was made by commenter Werther that shows the calvings (in blue and red):
Those are pretty big calvings, but strangely enough, I haven't seen any reports anywhere (of course, the Cruise-Holmes divorce must take precedence). A big calving of 7 square km in 2010 received more attention. I did a blog post on it at the time, with more general info on Jakobshavn Glacier. Here's a spectacular image of Jakobhavn's calving front from April 21st 2012.
Here's an animation that starts with an image of June 30th last year, and June 4th and June 30th this year. Keep your eye on the south branch (lower left):
I finish this blog post with two images that show what things look like on the ground. The first image is again from Dr Box's blog with the following explanation: "This is how much darker the Greenland ablation area is than a fresh snow surface that blankets it in wintertime. Along much of the southwestern ice sheet at the lowest 1000 m in elevation, impurities concentrate near the surface and produce this dark surface. Not all of the ice sheet is this dark, only the lower ~1/3 of the elevation profile of the ice sheet is. However, as melting increases on the ice sheet, so does the area exposed that is this dark."
The other photo is from this NOAA ClimateWatch Magazine article and was made by Henrik Egede Lassen/Alpha Film, from the Snow, Water, Ice, and Permafrost in the Arctic report from the U.N. Arctic Monitoring and Assessment Programme.
We will soon find out if 2012 has yet again broken the Greenland ice sheet reflectivity record. I agree with Gareth Renowden at Hot Topic that it looks likely. As Jason Box says:
What I expect we will see if these low albedo conditions persist is 100% surface melting over the ice sheet. This would be a first in observations. It may not happen this year, but the trajectory the ice sheet is on, along with amplified Arctic warming, will have the ice sheet responding by melting more and more.