Al Jazeera notes the big Navy presence in the Gulf.:

[O]n October 31, two nuclear-powered carriers, the USS Eisenhower and USS Enterprise, arrived in Bahrain, accompanied by their carrier strike groups. And on November 9th, the USS Iwo Jima, and the USS Boxer also arrived.

Is President Bush up to something? Asked Rense.com

On October 11, American officials announced that the U.S., Bahrain and other states will hold their first naval exercise in the Gulf to practice interdicting ships carrying weapons of mass destruction and missiles.

The exercises, organized under the U.S.-led 66-member Proliferation Security Initiative and the first to be based in the Gulf near Bahrain, across from Iran, came as Washington and the European Union member states are pushing for imposing sanctions including possible interdiction of ships on North Korea, following its announcement of carrying out nuclear test, and on Iran, which the U.S., backed by Israel and the EU, claims is preparing to produce nuclear weapons.

Iran considers Washington- sponsored war games in the Persian Gulf, off the Iranian coastline as a provocation aimed at creating a situation of direct confrontation between the U.S. and Iranian naval forces in the Persian Gulf, although a senior U.S. official insisted that the exercise is not aimed specifically at Iran.

About the exercises, which experts say reinforces a U.S. strategy aimed at strengthening America’s ties with the Gulf states, which Tehran and Washington are engaged in a fierce competition to win influence over, the official, speaking on condition of anonymity claimed:

"It’s an effort to bring a lot of Gulf states together to demonstrate resolve and readiness to act against proliferation."

I don't know if a four carrier deployment is significant, but perhaps some old salt (or not-so-old salt) can compare this deployment with past exercises in the region.