What I am hearing is a series of short bursts of noise, almost like a burst of machine gun fire. The length seems to be from 4 to 6 "bursts" in a group, although some have been two groups of 4 or more in a row. I can also heard weaker stations followed by bursts from stronger stations. Sometimes the bursts are at a moderate tempo, and some seem to be very rapid compared to others.
Here are some short clips of what I heard. Turn the volume up when watching these:
At first I wasn't sure if these noises were intentional or just some form of interference, but after hearing them and listening to the patterns, I am guessing they are intentional usage of the frequency by the Coast Guard. As to what this is used for and why they are using this frequency remains a mystery. Anyone want to guess at what's going on here?