I thought this merging oceans or ocean borders was the most unusual thing I saw on the Alaskan cruise in the water. These two bodies of water were merging in the middle of the Alaskan gulf and there was a foam developing only at their junction. I thought this was an example of a Halocline, which is a cline caused by a strong, vertical salinity gradient within a body of water. However, a few people have commented that a Halocline is more of a horizontal phenomenon and this is more vertically oriented.
I am pretty confident that what you are seeing is a result of the melting glaciers being composed of fresh water and the ocean has a higher percentage of salt causing the two bodies of water to have different densities and therefore makes it more difficult to mix. I’m told they will eventually mix given enough time. Anyway, whatever it is, the merging oceans surely an amazing nature event.