...it must be sea ice puzzle time. ;)
Here are four images of exactly the same location in the Arctic ice pack in four different years. They're from satellite infra-red, 3 are for roughly the same period, one is earlier due to a gap in image availability. The images have been selected for clear skies, ice state is typical, as shown by the persistent pattern of ice cracking. The location has been chosen as it should reveal changes in ice state being a mechanically 'interesting' location. The images have been rotated and/or mirrored, and land cropped out to hide the location, there has been no further manipulation of the images.
Which image is from 2013?