According to Google Earth there is a steep canyon-like valley S of that "gap". It seems that the once "united" glaciers has been divided by the melting water of that little river which flows through that valley. Older, but not very precise photos from the 1990s show an intact glacier. Around 2005 a large melt water lake has formed N/NE of that now "orphaned" part of the glacier which had drained afterwards, leading to that "gap".
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[You can look at older photographs in Google Earth by using the "historic picture button"]
I saw a similar thing happening early this century back in Iceland. Many of you who have visited Iceland will have seen the Jokulsarlon lake where the calved icebergs float around and are even flushed out to sea.
To the west of this lake there are a couple of other similar lakes such as Fjallsarlon which I used to visit evey time I could from 1991 up to 2008, and more sporadically since.
The first image shows the three lakes, the glaciers are all retreating fast and the lakes are growing, but the really dramatic changes that I saw happening were finished by 2008, which is the last time that I stopped and had a proper look.
That visit in 2008 I had a GPS for the first time, and I noticed that according to the map on the GPS I was actually parking my car on the glacier itself! In the second image I've marked my usual "parking spot" with a red cross, and the appr. glacier edge as shown on the GPS with a green line.
The yellow path shows where I used to walk up onto the glacier itself, the last time I did that would have been around 1996 or 7. The glacier was very smooth and flat in that area, simply because it had stopped moving and was just melting down.
The area of interest for this discussion is marked with a black circle. The small glacier tongue to the left used to merge with the larger one, and did so until about 15-20 years ago. The material underlying these glacier tongues once they reach flat land is mostly a huge pile of gravel and mud that the glaciers have been carrying down from above, and once the ice was removed from the top of this pile, the waters coming from further up started to carve it's way down through the rubble.
When I was there in perhaps 2004 I noticed that a very large canyon had suddenly appeared in the middle of the black circle, the following year it was gone since the canyon walls were essentially just gravel and mud, and the whole pile had probably just been washed away.
The third attachment is a photo I found on the internet after a surprisingly long search, unfortunately if you search for "Fjallsarlon" you get pictures of "Jokulsarlon" instead, it takes a local to tell the difference. The position and viewpoint of the photo is marked with a couple of brown thin lines in the second image. 30 years ago, the photographer would have been standing on the ice itself.
