On 25 June, the US Coast Guard announced that its only operational heavy icebreaker, the Polar Sea, was operational no longer. The ship had suffered 'an unexpected engine casualty' and limped back to its home port of Seattle, Washington, where it will undergo repairs until January 2011. A refurbishment in 2006 had supposedly extended its operational life to 2014. The announcement underscored the decrepit state of America's ageing icebreaker fleet — a situation with many troubling implications for the United States, not least its ability to carry out Arctic and Antarctic research.

The Polar Sea and its sister ship, the Polar Star — which is also in dry dock, undergoing a refurbishment scheduled to last until 2013 — are the only US ships able to cruise through ice up to 1.8 metres thick. Both are past their 30-year design life and are increasingly expensive to keep in repair. Yet no funds are available to replace them.

There is no mystery why. The Coast Guard's parent agency, the Department of Homeland Security, is focused on terrorism. The Coast Guard itself is overextended by its responsibility to protect American territorial waters and US operations in the Gulf in the Middle East. And the US Congress, faced with the estimated US$2 billion replacement cost for both vessels, has routinely found sexier priorities for the money.

Yet icebreakers are essential for carrying fuel and supplies to the main US Antarctic base at McMurdo Sound, which in turn supports most of the American research activities on Antarctica. Icebreakers are also crucial at both poles to open the way for scientists to study water below the ice, including biological productivity and processes such carbon cycling.

The good news is that the Polar Sea's breakdown will have little immediate effect on research. Since 2006, the US National Science Foundation (NSF) has been leasing the Swedish heavy icebreaker Oden to keep McMurdo supplied. And the Coast Guard has been supporting Arctic science through its medium icebreaker, the Healy, ever since that ship was commissioned in 1999. The Healy can only cruise through ice up to 1.4 metres thick. But unlike either the Polar Sea or Polar Star, it has extensive built-in laboratory space and research instrumentation. In addition, the NSF operates two smaller research vessels with some icebreaking capability.

In the long haul, however, this make-do system is inadequate. Scientific interest in both polar regions is increasing rapidly — not least because of the profound changes being triggered there by global warming. And commercial interest in the Arctic Ocean is also growing as more of the water remains open for longer periods every year, and as pressure mounts for offshore oil and gas exploration. In that environment, the United States needs a robust, four-season, heavy icebreaking capability for essential duties such as supporting science, mounting rescue operations and helping to clean up Arctic oil spills.

This point has been made repeatedly in recent years by concerned parties such as the US National Academies, the Coast Guard and the Department of Defense's Pacific, Northern and Transportation Commands, all to little avail. However, a bill pending in Congress would authorize the Coast Guard to undertake a cost–benefit study of upgrading or replacing the nation's existing icebreaker fleet or of doing nothing.

Congress should pass that bill without delay. And polar scientists need to become active participants in the ensuing debates. They cannot expect a blank cheque; costs do have to be balanced against benefits. But they can try to ensure that the study includes a clear-eyed assessment of what the research priorities are, what icebreaking capabilities will be required to support those priorities and how to allocate costs and responsibilities between agencies such as the Coast Guard and the NSF.

Icebreaking is not a glamorous job. But it is essential to US interests and the long-term health of polar science.