The Siren Board

I was streetviewing around tonight on the Midway Island and found what appears to be a Sentry. A newer sentry at that! I know the US Dept of Wildlife has some work on the island, but I don't know of any military activities that take place on the island anymore. Wonder what the siren is used for.

https://goo.gl/maps/1AOTt

Possibly used for wild fires?
Here is another view I found of it:

It's also a reasonable guess that it could be used for tsunami or hurricane warning.

Very interesting find, too - with only 60 people at most on the atoll it's surprising they'd need something of that size.