Details, Beginning withing a few kilometers of the outlet of Jakobshavn there is a near linear features running very close to SE for 75% to 80% of the distance across the island. The feature is somewhat irregular in the lower, faster moving sections, from there it becomes quite liner and narrow for a considerable distance. When the feature reaches the upper elevations of the ice cap it becomes less liner and more variable in width. As it approaches an area of apparent irregular topography influenced by bedrock (or an area of clouds?) it appears to widen slightly into a fan shape, opening toward the high ground. Just east of this, assumed, high ground the feature may be seen again, slightly offset but still bearing SE. The feature fades before bedrock influenced topography is apparent, nearing the east coast.
Conditions appear to be quite clear as surface details are discernible both SE and NW of the feature. A vapor trail perhaps? This should be checkable. Conditions on the 29th are much cloudier, especially to the east. I saw this and headed to the forum to ask about it and was greated by those two old maps, very apropo. The feature is obvious at all pixel sizes from 4K to 250m. It looks like a giant slump.