WASHINGTON — As more of the Arctic Ocean becomes open for shipping, the United States isn’t prepared for potential disasters such as the Deepwater Horizon spill in the Gulf of Mexico, top U.S. Coast Guard and U.S. State Department officials told a Senate subcommittee Wednesday.

Coast Guard Adm. Robert Papp said that when the Deepwater Horizon explosion occurred in spring 2010, the Coast Guard was able to deploy manpower and resources from its numerous bases in the Gulf of Mexico to assist in cleanup and recovery efforts.

In the Arctic, the Coast Guard has limited resources and infrastructure, he told a subcommittee of the U.S. Senate Commerce, Science and Transportation Committee.

If a similar spill occurred in the arctic, “We would have nothing,” Papp said. “We’d be starting from ground zero.”

David Balton, deputy assistant secretary of state for oceans and fisheries, also drew a comparison between the Deepwater Horizon disaster and the U.S. response to a spill in the arctic. Federal agencies hadn’t anticipated how to respond to a worst-case scenario in the gulf and the same is true in the arctic, he said.

Environmental changes in the arctic, such as rising temperatures, melting sea ice and changing ecosystems, combined with new technologies, are opening new possibilities for human activity in the region, including ocean shipping, oil and natural gas development, mineral ore extraction, commercial fishing and tourism.

But the added activity creates risks. Greater shipping traffic through fishing areas and increased oil and natural gas exploration raise the risk of accidents.

Energy exploration is under way but the existing infrastructure is limited.

Pete Slaiby, vice president of Shell Alaska, which hopes to begin its exploration drilling in Alaska next year, said drilling, cleanup and well-control technology improved as a result of the Deepwater Horizon oil spill.

Shell vessels will respond to spills within 60 minutes. In the worst-case scenario, he said the company is prepared to recover 25,000 barrels of oil a day via mechanical skimming alone. Shell wells will be accessible by both divers and remote-operated vehicles.

“I believe we have the best oil response plan in the world,” he said.

The Coast Guard is examining what it will need in the next few decades to fulfill its roles in the arctic, Papp said. He said its most immediate need is a seasonal facility to base crews, hangar aircraft and protect vessels to mount a response.

Balton said it would take several years to meet minimum requirements of preparedness.