Nice observation, Terry. Yes, the sea is what the Gulf is -- "empty and desolate" is what its character is, indeed, at least here.
However, I don't find the Gulf claiming the old man -- he is driven by the Trades to a sleepy corner:
.  .  .  "Gull against the wind, in the windy straits 
Of Belle Isle, or running on the Horn,
White feathers in the snow, the Gulf claims,
And an old man driven by the Trades
To a sleepy corner."

--- On Thu, 3/11/10, Terry Traynor <[log in to unmask]> wrote:

>the phrase, "the Gulf claims," still is a puzzle.

Maybe because "the Gulf" seems to me to be a watery abyss, as in TWL's "Oed' und leer das Meer" (void and dark the sea), I read "the Gulf claims" as noun then verb, with three direct objects for the verb: the gull (both against and with the wind), the white feather in the snow, and the old man.