This article in the Guardian is deeply disturbing. It says that the dedicated CryoSat 2, has found that the rate of Arctic Summer sea ice loss is about 50% higher than most current scenarios suggested. Part of the "surprise" is the dramatic thinning of the ice, which is now able to be accurately measured.
With the loss of the white ice to reflect back some of the solar radiation, the area will warm faster. With the recently reported plumes of methane already showing, the big, scary worry is a massive loss of methane to the atmosphere as in the "clathrate gun hypothesis", followed by how the warmer summer water will affect the Greenland ice sheet. On a different, but also worrying note the likely rush for oil, gas as the region becomes more accessible is likely to have a huge negative impact on the region and add more to our burden of greenhouse emissions.
The arctic region has also offered a last sanctuary to some species of fish (like Cod), and as it opens up, we are likely to the usual overexploitation resulting in collapse.
With Rosneft, Shell, Exxon, Chrevron, Statoil, Cairn and all the rest lining up, backed by the appropriate governments, the outlook does not appear rosy.