ANCHORAGE, Alaska: The grounding of an oil drilling ship on a remote Alaskan island has refueled the debate over oil exploration in the U.S. Arctic Ocean, where critics for years have said the conditions are too harsh and the stakes too high to allow dangerous industrial development.

The drilling sites are 1,600 kilometers from Coast Guard resources, and environmentalists argue offshore drilling in the Arctic’s fragile ecosystem is too risky. So when a Royal Dutch Shell PLC ship went aground on New Year’s Eve on an uninhabited island in the Gulf of Alaska, they pounced – saying the incident foreshadowed what will happen north of the Bering Strait if drilling is allowed.

For Shell, which leads the way in drilling in the frontier waters of the U.S. Arctic, a spokesman said the grounding will be a learning experience in the company’s yearslong effort to draw oil from beneath the ocean floor, which it maintains it can do safely. Though no wells exist there yet, Shell has invested billions of dollars gearing up for drilling in the Beaufort and the Chukchi seas, off Alaska’s north and northwest coast.

The potential bounty is high: The U.S. Geological Survey estimates 26.6 billion barrels of recoverable oil and 130 trillion cubic feet of natural gas exist below Arctic waters.

Environmentalists note the Beaufort and the Chukchi seas are some of the wildest and most remote ecosystems on the planet. They also are among the most fragile, supporting polar bears, the ice seals they feed on, walrus, endangered whales and other marine mammals that Alaska natives depend on for their subsistence culture.

Shell Alaska spokesman Curtis Smith said the company has a long, successful history of working offshore in Alaska and is confident it can build another multidecade business in the Arctic.

“Our success here is not by accident,” Smith said. “We know how to work in regions like this. Having said that, when flawless execution does not happen, you learn from it, and we will.”

The grounding in the North Pacific is not a wellhead blowout in the Arctic, and not a drop of oil has been detected in the water. But environmental groups say it’s a bad sign.

Arctic drill rigs could be affected by severe weather any time during the four-month open water season, said Marilyn Heiman, U.S. Arctic director for the Pew Environment Group.

“We know that in the Arctic and in the gulf it’s not uncommon to have pretty high seas,” she said. “You have to have strong, Arctic-specific gear and equipment and safety training. It has to be very vigorous, and I don’t think we’re there yet.”

Shell was fortunate in some ways, she said, that the Kulluk experienced problems near Kodiak.

The drill ship that operated in the Beaufort Sea, the Kulluk, a circular barge with a funnel-shape hull and no propulsion system, ran ashore Monday on Sitkalidak Island, which is near the larger Kodiak Island in the gulf.

The ship had left Dutch Harbor in the Aleutian Island under tow on Dec. 22. It was headed to a Pacific Northwest shipyard for maintenance when it ran into a vicious storm – a fairly routine winter event for Alaska waters.

The towline snapped on Dec. 27. Shell vessels and the Coast Guard reattached towlines at least four times. High wind and seas that approached 15 meters frustrated efforts to control the rig, and it ran aground on a sand and gravel beach.

Calmer weather conditions Wednesday allowed a team of five salvage experts to be lowered by helicopter to the Kulluk to conduct a three-hour structural assessment.

It was no accident, Smith said, that additional vessels had been standing by in Seward.

It’s too soon to know what led to the grounding, Smith said, but the failure of the Aiviq’s engines for a time after the initial separation and the inability to re-establish an ideal tow connection were factors.