Compare the two Landsat images from June 24, 2014, and September 19, 2014. At this high latitude, the sun angle becomes very low later in the year.
The June 24 image is close to the summer solstice. The September 19 image is close to the autumnal equinox, when the sun angle is much lower in northern Greenland. This lower sun angle is very noticeable in the longer shadows. The shadows also provide hints about the height and shape of the mountain peaks along the glacier.
Landsat does not acquire images this far north during winter. In the Northern Hemisphere’s winter, it becomes too dark for satellite imaging.