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Tour of duty Breaking ice big time in the Antarctic December 20, 2000 One of the largest icebreakers in the US Coast Guard fleet, the Polar Sea, is off the coast of Antarctica as the sea ice begins to melt around this icy continent. Every year either the Polar Sea, or its sister ship the Polar Star, heads south primarily to break a channel through the ice to McMurdo base on Ross Island. But along the way these ships, which play host to National Science Foundation academics and their projects, repair a string of automatic weather stations along the Adelie Coast and carry out experiments which help scientists understand the wild nature of earth's most southern continent. The Seattle-based ice breaker Polar Sea doing what it knows best: busting pack. Hard to predict "The weather in Antarctica is hard to predict at the best of times, yet there are fewer data input stations there than for a city the size of Boston," says Polar Sea's commander Steve Wheeler - a native of Medford Massachusetts. Satellite pictures help, but 'you can't tell everything from satellite photos', says Wheeler and, besides, the satellites that service Antarctica shut off over the continent to save battery power. The result can be clearly seen on composite Antarctic satellite photos, visible as a black wedge rotating around the continent. "It's just one of those things," says Wheeler, a vetaran of 10 years of Antarctic duty and equally experienced in the high Arctic. "There are so few users, greater coverage can't be justified. It's the same with nautical charts. The coverage for down here is terrible, but there are so few users ..." Sailing south From Hobart on December 14, the 399 foot icebreaker sailed south, passing behind a deep low south of the island, but feeling the affects of the storm's 5-6m swell. Sailing beam on, the ship rolled something fierce. Another weak front passed over the ship a day and a half later, with moderate effect, but a deep low three days behind and coming in from the west was too far north by the time it passed south of Australia and New Zealand to affect the Polar Sea's passage: At a speed of 17 knots, the 1200 nautical mile crossing only takes the Polar Sea four days. For 10 days from December 18 the Polar Sea ran east along the Adelie Coast, working close to the pack ice and flying its two on-board helicopters to each weather station, up to 60 miles further south to carry out repairs. Wheeler says these stations - built along one of the windiest coasts on the continent and home to the famous Katabatic winds - take a severe hammering every winter. One station blew away completely, with engineers finding only a few nuts and bolts. Regular maintenance always includes replacing anemometers, which get blown away after winds routinely reach speeds of more than 130 knots. Rough sledding The real fun starts after the ship rounds Cape Adare. By December 28 Wheeler aims to have pushed through 200 miles of rough sea ice (rough sledding, as he puts it) to lie at the edge of fast ice some 30 miles north of McMurdo at the edge of the Ross Sea Ice Shelf. But the real issue for the Polar Sea is negotiating the sea ice band surrounding Antarctica. "There is a LOT of ice banded from about 145E, out further than the Balleny Islands, and extending clear across the opening to the Ross Sea," says Wheeler. This is the stuff we have to push through (usually right down the dateline) just to get into the Ross Sea. "This year seems thicker," he says. "Maybe there haven't been as many coastal storms to push the ice around. It might have been a calmer winter and more chance for the ice to form. But it's nothing we can't handle." As the ship heads south, it encounters the Ross Sea, an area of recurring open water (about 60 per cent ice, 40 per cent open water). "You push through the sea ice headed into the Ross Sea, and you actually reach more open water the further south you get," Wheeler points out. "The Ross Sea phenomena is called a recurring Polynya - a non-linear opening in the ice due to warmer water, faster moving water, or anything that will inhibit ice growth: North facing cliffs reflecting heat into the surrounding bay; upwelling currents carrying warmer bottom water, localized continuous wind, etc." About 30 miles from McMurdo base, the ship will meet ‘fast ice’. Fast ice is "made fast" to the land, says Wheeler. In the southern Ross Sea, there is a shelf of fast ice that lies between Ross Island (where McMurdo is) and the Antarctic continent, about 40 miles to the west. At this point pure grunt is all that will get the ship through. While the ship runs on diesel-powered electric motors in open water, once in the ice she fires up three gas turbine engines to produce 60,000 horsepower. Now that’s a lot of grunt. But there is something in the ship’s favour this year: Wheeler says fast ice coverage surrounding McMurdo and the sea ice coverage in the Ross Sea are running slightly lower than average. He notes that at that latitude - about 77 degrees south - there have been lots of storms to break it up.
Tricks of the trade Getting through the ice band surrounding the Antarctic continent involves plenty of experience, and more than a few traditional tricks. It is not just a matter of looking at a satellite image and opening the throttle. Satellite imagery is great, notes Wheeler and it has saved his ship a lot of money finding holes in the ice. In fact, the last upgrade of download equipment - the ships takes images direct from satellites and manipulates the image data on board - cost the ship US$120,000. However, Wheeler recalls spending US$60,000 in fuel driving his three gas turbines for 20 hours ploughing into a 'sucker hole' on one expedition north of Norway, so Satellite imagery certainly saves money. "But you've got to look at satellite information as a strategic thing," he says. Satellite pictures are good for showing flaws in the ice, the orientation of ice floes, leads in the ice and where polynyas (the 'secret seas' of open water where whalers of old hunted their prey) are likely to open up. "When you actually get into the ice, it is very dynamic," Wheeler says. "It moves all over the place. I've had the opportunity to travel 50-60 miles away from ship and have the helicopter fly away leaving me on the ice and it is noisy as hell. It groans. The ice moves all over the place. A lead showing in a satellite image that is six hours old may not be there anymore." In the old days, the ice conning tower was the best place to look for ice leads. Now helicopters are used to great affect - when they can get out and fly. "We do ice recon all the time," says Wheeler. "we pop up to 1000 feet and you can see each distinct ice flow. In the conning tower it is hard to pick out the difference between ridge lines and ice floes, and you may not see the open water behind. Whaling tricks Of course, the whalers of old did know a heck of a lot about ice navigation and their tricks still work well today. Two old favourites spring to mind: 'Ice blink' and 'water sky', both of which only work when there is low cloud and adequate visibility. Ice blink is the reflection of white ice and snow onto cloud above, showing the presence of pack ice, and even large bergs before they rise above the horizon. Water sky is the dark reflection of open water within pack ice, showing up as a dark line within the ice blink. Wheeler reckons these tricks of old work well and all of them are used by ice sailors in their quest for speedy transport through the ice. Know the future, know the past ... Trend, according to Wheeler, is essential. "You can't dump someone into a field of sea ice and expect them to meander their way into it," he says. Wheeler says his greatest challenge is getting into a polynya, any recurring opening in the ice, where sailors can expect a zone of six-tenths ice coverage surrounded by solid pack ice. Whalers of old called these polynyas the secret sea and counted on them to open before the surrounding pack in order to hunt their prey. Wheeler notes that the Inuit at Thule, Greenland, call their local polynya the 'north water' and relied on it for fish and, ultimately, survival. "It is real easy to find recurring polynyas in the Arctic - look for any old established Inuit or Eskimo settlement. Great places to hunt seal or fish," he says. The Ross sea is a polynya - and the Polar Sea will count on getting through pack ice by punching into these loose pools in order to save time and energy. Wheeler says he uses satellite photos to find early indications of where the recurring Ross Sea polynya will open up. He looks for small indentations along the edge of the pack, where ice may be only six tenths in concentration. Further south there might be solid pack and a little further on another patch of seven to eight tenths, and so on. Wheeler says he uses those patches of relatively open water to navigate quickly, and can afford to crunch through the solid pack knowing that easier 'sledding' is not too far away. Bowling down the date line: Right or wrong? Typically the Ross Sea polynia opens a couple of degrees either side of the date line, at 180 degrees of longitude. But not always. Wheeler says the polynya appears to be opening about 175 degrees west this year, and ice navigators must use their nose when it comes to successful transit. For instance, Antarctic explorer Robert Falcon Scott firmly believed that the polynya would open at exactly 178 west - where it did during an earlier expedition (Discovery, 1902). His passage through the ice in 1911 took him three weeks. To give him credit, there was very little historical data for him to use. However, the great Norwegian explorer Roald Amundson realised that the polynya opening changes from year to year. Perhaps his whaling friends had passed on some of their knowledge. Whatever the case, Amundson steamed along the edge of the pack until he found what he was looking for - a 'soft' indentation in the pack offering an indication of an opening and he took it. His passage to the coast took just three days! Studying history Wheeler has been studying modern Antarctic expeditions since the US sent a fleet down to McMurdo in 1947, called Operation High Jump. "I looked at that operation and they had the right idea based on meteorological background. They tried to bowl straight down the dateline. But you try to bowl your way around Cape Adare and if I'm running three gas turbine engines I can burn 60,000 gallons in 20 hours. That a lot of fuel if you find you're not getting where you want to go." Indeed, Wheeler found himself burning those 60,000 gallons after he accidentally meandered into a rubble field north of Norway, where there was no satellite coverage. He had no choice but to bowl his way out of it with grunt. "To navigate ice you need savvy and patience," he says. "If you can't find your way shut the boat off and wait for ice conditions to change." Weather on the world's largest iceberg One of the projects supported by the Polar Sea is to monitor the world's largest iceberg, B15, which broke off the edge of the Ross Ice Shelf last March. Wheeler says scientists aim to place a weather station on the berg itself, to see how local climate is affected by an intrustion of many mega tonnes of frozen fresh water. Iceberg ice is frozen fresh water, and millions of gallons melt off the underside of a berg every day in the open ocean. All that fresh water welling up alongside the berg must affect the surrounding salt water environment, but how? As well, fog is typically created on the lee side of large bergs, after moist maritime air blows across their icy surfaces. In cases of large bergs, that lee-side fog is clearly visible in satellite photos.
Katabatic winds Commonwealth Bay on the Adelie Coast is where Australian explorer Douglas Mawson over-wintered and eventually named the place 'home of the blizzard'. And with good reason, katabatic winds up tear down glacial valleys from the ice plateau 10,000 feet up creating wind speeds up to 150 knots (300kph), much like cold air dropping out of an open freezer door. Commander Wheeler recalls servicing an automatic weather station at the base of the Mertz Glacier a little to the east of Commonwealth Bay, and relaying a gut feeling to the ship's captain: 'Don't fly the helicopters today', he said. A thin black line was just visible way up the glacier and Wheeler, who swears he has an internal barometer, knew something was up. With limited flying time down on the Antarctic coast, the captain was rightfully keen to fly, especially considering the day: Clear, sunny and winds no more than 15 knots. But Wheeler persuaded him: That thin black line was getting thicker by the minute. It was a katabatic wind event, barreling down the glacial valley and kicking up dust and debris as it traveled. By the time the crew folded the chopper's blades, that black line had descended upon them and it was blowing 45 knots. By the time the crew pushed the chopper into the ship's hangar some 20 metres away, it was blowing 90 knots and they couldn't close the hangar door. Two hours later it was all over. "Antarctica is a place like no other," says Wheeler. "It gives you a real kick in the ass." The biggest, bad assed storm of all Commander Wheeler recalls one cold core hurricane which caught the Polar Star unawares on a voyage into pack ice. The centre of this low was south of 60 degrees and its frontal tail touched the Chagos Islands in the northern Indian Ocean. It was bad. So bad, in fact, that 10-12 foot waves were running through the pack ice, dropping chunks of frozen water on the foredeck. Crew frantically levered the ice back into the sea, and all the while floes and small bergs rushed past the ship. All three gas turbines were operating at their limit and despite the appearance of the ship travelling through the water, GPS readings proved otherwise: She was travailing at three knot backwards and continued to do so for three days. Did You Know? The Polar Sea is powered by diesel electric in open water and gas turbine powered in ice. With the three turbines going flat-chat, they produce 60,000 hp. Ice coverage is measured in tenths. Cloud coverage is measured in eighths. The clear, dry air of Antarctica creates a condition known as looming, when land over the horizon appears above it as light waves are bent around the earth's atmosphere. Wheeler saw looming first hand when the Antarctic coast was sighted 150 miles from land on one voyage south. This was in the days before GPS, so the navigator did some quick thinking before he realised what was going on! More great reading: Follow the Polar Sea’s progress through the Antarctic ice and its return voyage to Seattle. The captain's log is full of interesting observations!
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