Our arrival in base coincided with the arrival of the USCGC Polar Star, the only heavy ice breaker in the US military inventory. It’s presence allows a channel to be formed through the sea ice, which allows the annual resupply of the station by both a container ship and tanker.
McMurdo Sound was chosen by Scott in his initial Discovery expedition as it was the furthest south that you could sail when the sea ice was broken up, before hitting the ice shelf. Even though it is the middle of summer now, the sea ice will not always spontaneously break up and therefore a channel needs to be made.
Ice breakers are specifically designed with rounded bottoms to force themselves up on top of the ice and then use the weight of the ship to fracture the ice. They can also ram in to the ice to try and pry it open, but if it is in a big continuous sheet, then the ability of the ice to move sideways is limited until broken into chunks.
As a heavy icebreaker, the ship is rated to break ice up to 29 feet (8.8m), and the thickest steel lies in the bow, at around 2 inches thick. Interestingly, despite the might and scope of the US Navy and miltary overall, it only has two commisioned icebreakers, with one further in permanent dry dock. The other newer version is not capable of the challenges of the Antarctic, instead spending its time plying the northern reaches of the Bering Sea and North Pacific. Therefore, this 40 year old ship has been refitted several times to extend its life past the anticipated lifespan. Recently, the Coast Guard Commandant Admiral announced plans to biold two further heavy icebreakers with a $1 billion dollar (US!) pricetag each. Not exactly pocket change.
We had a chance to meet the Medical officer on board the Polar Star, as well as the dive team that wanted to see the hyperbaric chamber that is part of the hospital. That meant that we could angle our own private tour of the ship, excluding the operational engine rooms. Things on board a ship are pretty cosy. There is the normal galley, mess, bunkrooms etc. There is also a lot of entertainment and exercise equipment for prolonged deployments at sea. The bridge is fully automated, with a dissappointingly small wheel to steer the ship from. Out the back, there is helipad with hanger to take two Dolphin helos, although there are non onboard for this deployment. It has two props each with two diesel engines, as well as a third that is powered by a gas turbine, and used for increaed thrust when breaking ice. It can burn a phenomenal amount of gas when at full tilt.
The divers managed to get in the water for a dive to check out the hull and prop condition. They were saying, even using full dry suits, after 20 minutes in the water at around -2 degrees C, it felt like there was a leak in the suit, even though there was none detectable. Pretty austere diving conditions!
The ship will remain in the Ross Sea until both the container ship and fuel tanker have offloaded and cleared the area, in case anything goes awry. In the mean time, hopefully some more of the sea ice that has been broken will disperse and allow the whales that the crew had seen further out, in within viewing distance of us! Time is tight though until we go to the Pole so heres hoping!