Update, 5 p.m. Friday: An unmanned fuel barge adrift in the Beaufort Sea hasn’t run aground yet.

A Coast Guard aircraft from Air Station Kodiak got a visual on the small Canadian barge on Friday. Commander Shawn Decker says it’s about 20 miles north of Prudhoe Bay, floating west at three miles per hour.

"Right now, [based on] all of our computer drift models and after we actually saw it today, we are confident that it’s going to continue drifting past Prudhoe Bay," he says, "and it’s going to remain in open water for at least the next 12 to 24 hours." 

Decker says the Coast Guard is waiting to see whether it goes aground or gets stuck in winter sea ice before planning further response. He says the vessel may not spill its diesel fuel cargo -- about 950 gallons of it -- even if it does hit the coast:

"That part of the shoreline up there along the North Slope is fairly flat and it’s mostly gravel," he says. "So there’s not a lot of big jagged cliffs and rocks and things like that that could potentially puncture the fuel tanks."

Still, he says any fuel barge that’s out of control poses a threat -- so they’re notifying North Slope Borough communities of the situation. He says they’re working with the Canadian Coast Guard and the vessel’s owner, a large Canadian barging company, to keep an eye on the ship through the weekend.

The Canadian-flagged barge is 134 feet long, and was in Canadian waters when it broke loose from its tugboat amid high winds and seas. It’s carrying about 950 gallons of diesel fuel.

By Thursday, the barge had reached Alaska’s Arctic. U.S. Coast Guard commander Shawn Decker estimates it’s drifting west in ice-free water at a speed of three to four miles per hour. At that rate, he says it could reach Prudhoe Bay sometime late Friday -- and there aren’t any vessels nearby that could try to stop it:

"This time of year, on-water assets are very limited in that region," Decker says. "So right now, we’re coming up with other means to potentially track it, and then when it does -- or if it does come in contact with the shoreline, at that point, we can take action on it."

Right now, that means monitoring the barge visually, using Canadian and American aircraft. The vessel that was towing the barge went back to port in the Canadian village of Tuktoyaktuk after Monday’s storm, and is now iced in.

Decker says it’s not guaranteed the barge will run aground in Prudhoe Bay. It’s drifting between the Arctic coastline, and winter sea ice advancing from the north.

"One of the possibilities is the barge will become stuck in the ice," Decker says. "And if that happens, that’s going to create the next option for us to respond to it and to track it."

Either way, he says they weren’t able to visually locate the barge on Thursday, so they don’t know for sure where it’s drifting, or how fast. He says a Coast Guard aircraft from Air Station Kodiak will find the vessel again on Friday and try to drop a tracking device onto its deck.

This is the second drifting vessel near Alaskan waters in less than a week. The Russian cargo ship Simushir nearly ran aground on Haida Gwaii, an island chain off the British Columbia coast, last weekend. Stormy seas made it tough to get a tow line on that vessel, too.