It is 0330, half an hour before change of watch. The sun low in the southeast glares painfully onto the bridge. Here at sixty-two degrees south icebergs abound, radar looks like a polka dot quilt, and a continuous layer of pancake ice with nasty growlers on the surface and a two meter port beam swell from a gale to the northeast rolls the Aurora Australis twenty-five degrees. No one has slept much for two days; eyes are gritty. It is a challenge to keep awake with vague nausea, so inky black coffee with TimTams are all the go. A glucose and caffeine fix. Smokers have to rug up and brave the outside bridge deck at minus twenty degrees centigrade.
Welcome to the trials of polar navigation. High latitudes bring a range of challenges, varying ice conditions, visibility grossly reduced by snow and high winds, ships course dictated by the direction of ice leads, and where the open water or thinner ice prevails, all the time keeping south for our goal: the ice at sixty-four degrees, one hundred miles east of the Australian Casey station.
The heavy ice is broken by the ocean swells coming from the northern sector. The swells will fracture the ice sheet along lines parallel to the swell, so floes will be rectangles in a rough grid pattern. The ship will make entry and exit obliquely chasing down the leads until either fast (solid) ice is encountered going south (or open water, when making north on the way home).
Backing and ramming gets the ship through the thicker floes, or between them; into the fast ice to get the ice scientists out onto the sheet for research purposes; and closer to shore stations for safe resupply on ice thick enough to support ice vehicles. She can crack a floe, provided there is space between floes for the ice to move aside and create a passage for the ship to move ahead to another lead. It may take several rams to smash through a large floe.
Ramming with the angled bow rides the ship up onto the ice, and her weight will crack the floe beneath, advancing up to half a ship length, dependent on ice thickness.
Ramming is done at a maximum speed of six knots, to avoid hull damage and lessen the likelihood of getting stuck. Small amounts of helm are applied as she commences the ram, so she slews slightly, creating a small open water space alongside, so she can slip backwards for the next ram.
The rudder must be kept free of ice clumps, so it is always amidships when going astern (some icebreakers have an ice-knife behind the rudder), and no more than ten degrees, when going forwards. Consequently steering in ice is fairly approximate!
Backing and ramming is aided by several innovations.
- Slippery antifouling on the hull and low friction paint decrease ice adhesion to the hull.
- Lateral ballast water pumping from side to side allows the hull to rock rhythmically as she pushes through, helping to push and crush the ice sideways, creating a wider passage, allowing easier pullback, and less likelihood of becoming stuck. The lateral ballast tanks are also used at sea to decrease rolling, a feature of icebreakers, with their flattish bottoms to aid riding up onto the ice.
- Ballast water can also be shifted fore and aft, to loosen if she becomes wedged after ramming.
- The portside bridge wing helm position on the Aurora Australis overhangs a meter outside the ship's beam, so crew can see how tight the ice is alongside the vessel.
This activity can only be done in good visibility, where the geometry of floes can be seen. At night, when stationary, the propeller spins slowly forward to keep ice clear from the stern, otherwise there will be no progress with the dawn, as there is no room to back up with a frozen-in stern!
An awkward problem is getting encased (beset) in thick ice, with no room to manoeuvre. This can happen when the northerly winds blow the ice southward, in behind the vessel, closing the pack (as happened with this trip in November 2012). Similarly, when navigating too close to an iceberg, as both to windward and leeward are congestion pressure zones for ice. These multi-million-ton-plus masses of slow-moving ice, with 90% of their mass below the water, generate dangerous forces. Ships have been crushed, as when Ernest Shackleton's Endurance was lost in 1912
Freedom comes from either waiting (until the ice blows out, melts, or fractures) or, if more urgent, by creating a small pond around the ship, then progressing the pond across the floe by butting the ice ahead and using the propeller to push that ice aft, and then doing it all again about 100 times. At ten minutes each to gain a ship-length, about 200 meters per day, it is hugely expensive on fuel and wearing on crew. That's how the Aurora Australis became free after being beset for six days in 2012. In two and a half days, 600 meters were gained by belting the ice to get free.
Outside the pack and floes is the Medium Ice Zone, where ships are limited to eight knots, for safety; captains cannot risk hitting an invisible growler (small ice floe) at full pelt.
Here we find massive floating icebergs, house-sized iceberg remnants, and car-sized chunks of low floating ice (growlers) that can damage or put a hole in a ship. A careful double watch is kept at night-time and powerful searchlights are used to spot and avoid 'bergs.
In the Medium Ice Zone the plankton flourish. Nourished by the algae that grow within the ice, plankton use sunlight, with almost twenty-four hour daylight, and carbon dioxide from the atmosphere for photosynthesis. Frequent tiny ice channels, formed by the salt exuded from freezing water, makes for a rich pasture and provide the whales with their plankton diet. Whales are found in abundance at the ice edge, as the whalers of yore knew. This is the feeding grass of the world's oceans. This nutrient rich water will surface in the northern hemisphere, in a year or three. However, global warming may be killing it as the sea ice retreats.
Coming home, we are soon in open water, travelling northeast for Hobart, with the westerly swells pushing us along effortlessly at sixteen knots, accompanied by albatrosses, petrels, fulmars, and the occasional skua, another type of seabird.
We soon cross the convergence at fifty-six degrees south, with its dense fog banks created by warmer (seven degrees) seas meeting cold (zero degree) air, and then it is three days to landfall at Pedra Branca, a dramatic rock, twenty miles south of Tasmania where the smell of eucalyptus excites (one of the joys of returning from an Antarctic year), then the South Bruni light, and the Friars Rocks at dawn. Home on the Derwent, passing the John Garrow beacon, guarding Sandy Bay shoals, then Macquarie wharf, the bizarre customs and immigration inspection (where have we been!) and home at last.
So what is the medical practice like? Its mostly preventive stuff, seasickness on the way down; sunscreen as the ultraviolet is extreme and at a low angle; liaising with expeditioners to check that all five layers of clothing are worn and goggles for preventing snow blindness; doing regular recces (reconnaissance) on the ice; and checking for hypothermia (expeditioners often use bare hands for manipulating instruments), exhaustion (hand drilling meter thick ice), and dehydration. Hold evening clinics to deal with minor issues, and sail around the dining room to get any information on ailments.
We have two helicopters aboard, for ice science and ship reconnaissance. Pilots need extended first aid kits in case of a remote crash, where they may be stranded for days on ice.
A brilliantly equipped operating theatre, and a two bed ward complete the medical suite.
Previous expeditions have encountered multiple trauma from helicopter crashes, serious burns from engine room fires, compound fractures from closing watertight doors, appendicitis, pneumonia, frostbite, and penetrating injuries. Eternal vigilance begets prevention, as there is no assistance or evacuation from south of fifty-five degrees.
Satphone and twice daily email access allow contact with on-call personnel at base in Kingston, Tasmania, and digital photography helps with second opinions.
It is a wonderful seven-week voyage to a wonderland of ice, whales, seals, birds, stormy weather, and stunning sunsets in a part of the world unchanged for millions of years.
Bryan Walpole, MD, FACEM DTM&H, was the Expedition Medical Officer "SIPEX 11" on the SV Aurora Australis with the Australian Antarctic Division, November to December 2012. He graduated Monash University, Melbourne in 1967. He was initially qualified as a surgeon, then switched to emergency medicine in 1974, and was part of the founding of a college for Emergency Medicine in Australia and New Zealand. He directed three emergency departments in teaching hospitals, and in 1991 took a qualification in tropical medicine and was medical officer on scientific expeditions to the Antarctica and the North Pole. He currently practises in diving and hyperbaric medicine, and crisis work for companies with medical problems.