Shell Alaska spokesman Curtis Smith was quoted by The Associated Press in an email as saying that drilling was stopped as a precautionary measure.
"As a precautionary measure and in accordance with our approved Chukchi Sea Ice Management Plan, Shell has made the decision to temporarily move off the Burger-A well to avoid potentially encroaching sea ice," Smith said.
"Once the ice moves on, the Noble Discoverer will re-connect to anchors and continue drilling.
"We’re using satellite images, we’re using radar images, we’re also using onsite reconnaissance to watch this ice so there are no surprises."
The company is monitoring ice measuring 30 miles long and 12 miles wide, about 105 miles away from the drill ship.
Shell has spent about $4.5bn on its effort to drill Arctic oil; it had recently won a temporary permit awarded by the US Department of the Interior to operate its drilling rig.
The company is awaiting its oil-spill containment barge, the Arctic Challenger, to be approved by the Coast Guard, without which the Department of the Interior will not allow Shell to proceed with drilling operations.
Shell has made a request to the government to extend its oil drilling season beyond the 24 September 2012 deadline, reports the Associated Press.
Image: Aerial view of the Chukchi Sea. Photo courtesy of: P199.