The U.S. Coast Guard's last heavy icebreaker is leaving California after repairs to postpone its already overdue retirement.

The Polar Star is slated to sail away from the former Mare Island Naval Shipyard on Tuesday. Crews there carried out the latest maintenance to extend the life of the 38-year-old vessel.

Polar Star Capt. Matt Walker says the vessel is the only U.S. icebreaker still capable of breaking through the heavy ice of the Antarctic. The Polar Star in coming months will carry out the annual resupply of two U.S. research stations in Antarctica. Scientists there study the 1.5 million-year-old ice to learn the secrets of weather and climate change.

The Polar Star is eight years past its scheduled retirement date. Congress, the Obama administration and the Coast Guard have yet to agree on any possible funding for a replacement.