The U.S. two heavy-duty icebreakers are nearing the end of their useful lives, and there is neither enough money to maintain them nor a plan to replace them, according to a report from a panel of the National Academies, the country's pre-eminent scientific body. In a preliminary report requested by Congress, the panel said a lack of both money and a new generation of vessels could undermine the United States's ability to conduct defense, research and rescue operations in the Arctic and to open ice-clogged routes to supply American research stations in antarctica.

The report noted that commercial activity was increasing in the Arctic as summer sea ice melted. "This increase in human activity in more northerly latitudes will most likely increase the demand on the U.S. Coast Guard to have a greater presence in and around the ice margin to perform its many safety, security and law-enforcement missions," the report said.

The united states has three large icebreakers. The most powerful, the Polar Sea and the Polar Star, both built in the 1970's, can smash through floes more than six feet thick, but they were designed to last 30 years and need increasing amounts of maintenance. The third, the Healy, was built in the 1990's and is designed for ice about four and a half feet thick. The Polar Star, under extensive repairs in Seattle, is out of service until at least next fall. James Swift, an author of the report and an oceanographer at the Scripps Institution of Oceanography in San Diego, said of the Polar Sea and the Polar Star, "You're either going to have to invest a massive amount of money to basically rebuild the vessels or replace them if the U.S. is to stay in this game."