I have noticed that the Arctic seems noticeably darker over the entire expanse than the last couple of years, so I thought I'd try to make that more obvious by doing the following:
- Take the seven day period of June 20-26 in each of the 2013, 2014 and 2015 seasons.
- Average the seven images from each year together to smooth out effect of weather.
- "Dark-blend" the seven images from each year to eliminate clouds as far as possible
- Boost the contrast identically for each year's image to make the differences easier to see.
Here's what the result looks like. 2015 is clearly less reflective than either of the last two years. This is confirmed by histogram analysis, which shows a significantly lower mode than 2013 or 2014.
I didn't do the same for 2012 because the original images for that year don't look like they were processed consistently.
Edit: I should explain what the darken blending mode in Photoshop does for those who might be unfamiliar with it. Suppose I have two similar images stacked on top of each other. Normally, the top layer would completely obscure the bottom layer. However, if I set the mode to "Darken", then each pixel in the visible image would reflect only the darker pixel from image A and image B, regardless of which is on top. So if image A and B were identical except for a cloud that has moved within the frame, the cloud would magically disappear. By the same token, if image A is white ice with the exception of a crack that has moved to a new location in image B, the crack would appear in both locations in the final image. So the "darken" mode exaggerates the degree of fragmentation of mobile ice under clear skies.