As the massive amount of ice is in the water it releases a frozen energy constant which pushes any waves out to a point where the opposite temperature current meets it which gives it a calming look kind of like a slacktide in a bay where you have the water rushing in and the opposite water flowing out you will actually see a line between calmness and rough water.

THANX HUN! CRAZY 😁

You're welcome,
I see this all the time going over the Astoria bridge in Oregon. I will have to take a picture of it personally next time I go over.