Summer’s cruising — sultry days, balmy waters and a cool sundowner every afternoon. Well, not exactly.
Here we’re lucky if the temperature reaches the 30s each day; the water (where it’s not frozen) is 28° F, and there’s no liquor on the ship … which doesn’t matter anyway, since the sun never sets. Welcome to the Antarctic! With record temperatures as low as minus 128° F, wind speeds to 200 mph, and enough ice to raise the world’s sea level by 200 feet if melted, the Antarctic is a remarkable cruising ground — for the right ship.
I’m aboard the U.S. Coast Guard Cutter Polar Sea — one of three polar-capable icebreakers operated by the Coast Guard — for Operation Deep Freeze ’03. Based in Seattle, Polar Sea shares annual responsibilities with its sister ship Polar Star in logistics support of the U.S. Antarctic Program’s base at McMurdo Station.
Located at almost 78° S on the southern tip of Ross Island deep in the Ross Sea, “Mactown” is the home for much of the Antarctic research supported by the U.S. National Science Foundation. Although some operations continue here year round, the base’s primary activity takes place during the short Antarctic summer, from November to February. During this time also, two resupply ships — one cargo, one tanker — bring the bulk of the yearly supply of everything from paper clips to JP-5 jet fuel.
These ships have no capacity for icebreaking, so a polar icebreaker must make the annual trek from Seattle to McMurdo — about 8,170 miles direct — to open a navigable channel in the ice for the ships and to provide escort duty while the ships transit the channel. Last year’s exceptionally heavy ice conditions warranted a second breaker to be dispatched as well. While not engaged in the actual icebreaking tasks, the icebreaker also provides a platform for Ross Sea research projects, taking marine-science parties onto the Ross Sea — whether iced over or not.
Although home-ported in Seattle, the 157 crew of Polar Sea spend much of their time afloat on long-term missions like Deep Freeze ’03. For this operation, the icebreaker left Seattle on Nov. 4, 2002. Ports of call enroute included Honolulu, Sydney — where I joined — and Hobart, where the rest of the science team came onboard. After two months of continuous ice operations in the McMurdo Sound area, the ship returned to Seattle, arriving in late April — a total deployment time of almost six months! Mark Miller, captain of Polar Sea, quoted the ship’s motto: “The world is our op-area.”
Since commissioning in 1977, Polar Sea has seen duty in both the Arctic and Antarctic regions in support of science missions. In fact, on Aug. 22, 1994, the vessel became the first U.S. surface ship to reach the North Pole.
Polar Sea alongside the ice pier at McMurdo. With a hull thickness of almost 2 inches of low-temperature-resistant steel on the ice belt, the cutter is capable of breaking ice up to 21 feet thick.
Built by Lockheed Shipbuilding of Seattle, Polar Sea is 399 feet and 13,190 tons of icebreaking steel. Considerable strength is derived from the close &mdash about 16-inch &mdash spacing of the hull frames. With almost 2 inches of low-temperature-resistant steel on the ice belt, the ship is capable of breaking ice 21 feet thick.
The hull form of an icebreaker like Polar Sea is rounded to facilitate riding up onto ice during breaking operations and to protect the ship from ice pressure. Unfortunately for the crew, this round characteristic also gives the ship a particularly rolly ride, earning the ship the nickname “Polar Roller.”
The ship’s main propulsion is diesel-electric &mdash diesel generators powering electric motors. For each of the three shafts, a 16-cylinder Alco 251F 3,000-hp diesel engine turning a Westinghouse AC generator produces electricity, which is rectified to power a massive Westinghouse DC electric motor, whose rotor is the shaft itself. Drive thrust comes from three four-blade controllable-pitch propellers, each 17 feet in diameter and weighing 46 tons. In this 1-1-1 configuration, the ship cruises open water at about 11 knots. Speed and direction of propulsion are varied by adjusting prop pitch while shaft rates are held steady around 110 rpm. If less power is required, the wing shafts can be taken offline and the ship driven on the centerline alone. If more power is required, a second Alco/Westinghouse diesel generator can be powered up for each shaft. The 2-2-2 setup yields 18,000 hp and allows a cruising speed of 17 knots.
While this mere 18,000 hp may be sufficient in open water or light ice conditions, for serious icebreaking, Polar Sea fires up its three Pratt & Whitney MPL-4 20,000-hp (continuous) diesel-fired gas turbines &mdash essentially jet engines. With these powerhouses running, there’s a constant, muted background roar throughout the ship, similar to riding in a jet airliner. Each turbine drives a shaft through a massive Philadelphia 75 VMGS reduction gear. At peak power with “three turnin’, three burnin’,” the ship is breaking ice with 75,000 hp &mdash it is the world’s most powerful non-nuclear icebreaker. Little stands in its way.
While Polar Sea can break through the most difficult multi-year ice running on turbines, it can only do so for a limited time. In this configuration, the ship is burning 4,600 gallons of diesel fuel each hour &mdash keep this up all day and it amounts to almost 10 percent of Polar Sea’s total 1.3-million-gallon capacity. Since weight plays an integral role in icebreaking, fuel management is a consideration in the methods and power used at all times. Using combinations of diesel and/or turbine power among the three shafts, the ship can be configured in the most economical way consistent with the current ice conditions. Still this is not a fuel-frugal endeavor. Miller noted, “I’ve burned more fuel in a day here than I did in a month on my last assignment.”
Icebreaking 101: light duty
The strategies for icebreaking are as varied as the types of ice encountered. According to Operations Officer Lt. Cmdr. Tom Wojahn, “Strategy number one is avoid the ice in the first place.” At the outer reaches of the pack ice &mdash sea ice broken off from the continent and blown northward each summer &mdash large openings, called leads, form between adjacent floes. Depending on the density of the pack ice, leads can be anywhere from a few feet to hundreds of feet wide, and the ship will go several miles off its planned course to find the easiest route through this area.
When the icebreaker is in the ice, the ship is driven from 104 feet in the air, atop the mast in the aloft conn. The view to the horizon is 12 miles from this height, and the ship is constantly being steered toward the best-looking leads or the most vulnerable-looking floes. One of the two Aerospatiale HH-65A Dolphin helicopters is dispatched on occasion to search out the most promising-looking routes. But eventually, the ice closes in.
|The author at the rail of Polar Sea. A voyaging sailor, he was assisting the science team onboard.|
Generally speaking, the farther south one gets, the denser the pack becomes &mdash floes get larger and more tightly packed; leads get shorter and narrower; and blind leads are more prevalent. Although this area primarily has individually floating floes, there are places where one has been forced atop another through the natural movements of the ice pack, and in some large floes, pressure ridges form. These areas multiply the difficulty of the ship’s task in close pack ice, making maneuvering more difficult and slowing the ship as the actual icebreaking takes longer to effect.
Dec. 20 &mdash The sounds and sensations of icebreaking fill the ship as the bow slices through floes. The broken halves, 4 feet thick and up to 20 feet square, grind their way up the sides of the hull and surface about two-thirds of the way aft. The ship is essentially forcing itself between two solid ice masses, grinding steel against ice all the way. Sleep is a challenge. We entered the pack ice at about 69ï¿½ S and are working our way down more or less along the dateline. Floes of ice &mdash in sizes ranging from pianos to city blocks &mdash float on the sea surface, gaps of varying size in between. We pretty much drive right through this open pack ice at 6 to 10 knots, occasionally spotting AdÃ©lie penguins and Weddell seals.
The one exception to the “more south, more ice” rule is a polynya &mdash an area between the pack ice, which is being blown north, and the more stable fast ice that is still more or less attached to the continent to the south. This area is a vast sea of open water that changes with the weather and the season as fast ice breaks out and drifts north to join the slowly melting pack ice.
Icebreaking 102: heavy duty
South of the polynya comes the fast ice &mdash miles and miles of frozen sea surface. The fast-ice area varies considerably from year to year and will decrease naturally over the Austral summer. At this time of year, the outer edge is thinner first-year ice &mdash ice formed during the previous winter. Closer to land, the ice thickness increases continuously, transitioning to multi-year ice: older, thicker, less saline, inherently stronger and considerably more difficult to break.
In thick, multi-year ice there’s little subtlety to icebreaking. The technique is called backing and ramming, and it is the most forceful icebreaking method the ship can use. As the name implies, it’s a simple, repetitive procedure: Get a running start; hit the ice; ride up onto it until you stop, letting the weight of the ship break through; then back up and do it again right on the bow’s old imprint. The technique is costly, as the turbines gulp down fuel, and the ship’s machinery, systems, hull &mdash and crew &mdash are subjected to the constant beating, all for the sake of progress measured in fractions of a boatlength.
The ice channel
Grab a harbor chart of any commercial port, and you’re likely to see a deep-water shipping channel neatly delineated, properly sounded, buoyed and lighted. If you take a look at the McMurdo Station and Vicinity chart, all you’ll see is the open water of McMurdo Sound with some sketchy soundings. What’s missing of course, as of our arrival on Dec. 21 this summer, is that the navigable waters stopped 52 miles from McMurdo Station. Satellite images and limited coring suggest that the first 17 miles will be first-year ice less than 3 feet thick. Beyond that, the ice thickness will increase to about 10 feet and transition to multi-year ice. The last 5 miles to Winter Quarters Bay is all multi-year ice about 11 feet thick and topped with snow.
The thinner, outer ice yields easily to the icebreaker’s advances, and the progress is initially measured in miles per day. The deeper into the fast ice that we venture, the more tedious the task becomes. We are trying to cut a straight channel on a bearing of 143ï¿½ T straight to Hut Point, so we no longer chase openings or vulnerable spots. After 31 miles of relatively quick progress, we’re slowed dramatically and the brute-force backing and ramming begins.
Jan. 15 &mdash Each evolution into the ice channel takes about 10 minutes, beginning smoothly as the ship gains momentum, aiming for the imprint in the ice that marks the last thrust’s progress. The ship hits the ice at about 7 knots, and the bow is forced up and onto the ice surface. We slow noticeably, and under the weight of the massive bow, the ice breaks from flexure; broken floes are forced under the ship only to surface alongside. The whole of the ship shudders and shakes as the propellers find the remains of floes and mill them with huge blades; Polar Sea slews sideways and lists and hops around enough to move equipment around on lab benches. As the engines whine and the shafts rumble and the propellers churn, the sounds of grinding hull against ice emanate from everywhere. Anything not bolted down starts to pound with the vibration as the combined power of the three turbines force 13,000 tons a few more feet across the resisting ice. This is heavy-duty icebreaking. In two minutes we’ve made about a half-boatlength of progress. Then it’s calm and quiet; the props are reverse-pitched, and we back up into the brash of our recent handiwork to get the next running start.
After so many years of avoiding shallows, rocks and shoals, I can’t get used to the idea that we’re purposefully ramming this ice pack. Over and over and over.
At the end of the ice channel in Winter Quarters Bay, a turning basin is cut to allow the resupply ships to maneuver for their final approach and to turn around when leaving. This is initially cut as a circle about half a mile in diameter and then worked around and across until the entire interior is broken into smaller brash.
Then a final short channel is cut up to the pier. Not your average pier this. It’s called the ice pier &mdash a 200-by-540-foot solid mass, made from layers of freshwater ice and gravel reinforced with rebar, remelted and fused, floating in 60 feet of water, rising and falling with the tides.
With the initial cuts finished, the difficult task of grooming begins. At this point, the channel is 20 miles long, a ship-width wide, and filled with the large remains of ice broken on the initial passes. The icebreaker must widen the channel and break up the chunks into brash small enough for the resupply ships to pass through.
Seven miles from McMurdo, the channel narrows to about 150 yards; the ice too thick and the pressure too great to warrant breaking it out any wider. In these confines, maneuvering even the few degrees needed to attack the channel edge exposes the outboard wing shafts and propellers to unbroken ice. Turning is performed carefully, and power is applied only when the wings are certain to be clear to avoid potential damage. In spite of the best precautions, Polar Sea’s starboard-side propeller is damaged catastrophically as a blade is sheared off. The final channel grooming has to be performed on two shafts, aggravating the task of steering the ship in ice and limiting the power that can be brought to bear. A second polar breaker is dispatched from Seattle. It will take weeks to arrive.
Feb. 7 &mdash For 10 days now, we’ve been continually running the 7 miles of the ice channel. The whine of the turbines and the constant grumbling and shaking of the ship have become commonplace and are noticed now only in their absence when we stop for helo-ops or due to a breakdown. The Coast Guard cutter Healy has joined us now, and we both groom the channel and turning basin 24-hours a day, seven days a week. The cargo ship American Tern has been waiting for several days, neatly tucked in a parking space of ice cut earlier by Polar Sea.
The weather hampers the operation’s progress. The approach bearing of the channel is based in part on the prevailing southeast winds, relying on them to blow out brash and to reduce pressure in the outer pack. This year, steady easterly conditions and extremely cold temperatures continue to cause the broken ice to refreeze into ice breccia, demanding continual grooming all along the channel, basin and pier. Foggy days may be the worst, though; not because of limited visibility, but because the intake stacks for the turbines ice up, the reduced air flow effectively choking our main means of propulsion.
Miles to go
Although the resupply route is now cut, the refreezing of the remaining ice still makes the channel impassable for the conventional ships performing the resupply operation. The 521-foot, 17,000-ton containership American Tern and the 615-foot, 39,000-ton T-5 tanker Richard G. Matthiesen are both ice-strengthened, but they are not icebreakers. Though they have features like hull strengthening, protection for propellers, and heating elements to prevent ballast tanks from freezing may be present, but these ships can easily be beset if the ice conditions are too dense in the channel or too much refreezing occurs.
A modern ice-strengthened ship can suffer being beset in ice without incurring significant damage, provided of course that it has sufficient fuel to keep generators operational and sufficient food to keep crew operational. The greatest risk is being forced into shoal grounds by the constantly moving ice. On June 14, 2002, the German cargo ship Magdalena Oldendorff, with over 100 persons onboard, was beset in ice off the Antarctic coast while returning from a resupply mission for the Russian Antarctic base. To effect rescue, the Argentinean icebreaker Almirante Irizar was dispatched. The Chilean vessel was also subsequently trapped in the ice, but not until after it refueled and resupplied Oldendorff. Helicopters from the South African icebreaker Agulhas eventually rescued the science party and part of the Oldendorff crew. Irizar freed itself on Aug. 7, but it wasn’t until Nov. 25 that the ice loosened enough to permit Oldendorff to sail away.
The consequences of American Tern or Richard G. Matthiesen becoming beset and unable to fulfill their missions could be devastating to the U.S. Antarctic Program. Tern has onboard about 85 percent of the annual supply needs for the McMurdo and South Pole stations; Matthiesen brings essentially all of the annual fuel requirements. These ships are the lifeline that keeps the Antarctic program operational.
After much work, including a tow at one point, American Tern is safely secured to the ice pier. There’s a palpable sense of relief and accomplishment on the bridge of Polar Sea as well as a round of well-deserved congratulations, thanks and the VHF-radio equivalent of backslapping before both icebreakers motor out and heave to for the first quiet night in weeks.
Eventually Polar Sea’s mission is complete. American Tern is escorted out and Matthiesen, made fast to a temporary ice mooring, is offloaded through four miles of pipeline before being escorted north through the rethickening pack ice. Then and only then, a tired but proud crew points Polar Sea’s bows northward, away from the crepuscular Antarctic sky &mdash and the impending winter &mdash and toward the tropics and home.
The author would like to thank Capt. Miller, the officers and crew of USCGC Polar Sea for their unreserved hospitality during Operation Deep Freeze ’03 and for freely sharing their knowledge of the ship and its operations; and Dr. Vern Asper of the University of Southern Mississippi for the unique opportunity to join the research team for this deployment.
Jeff Williams and his partner Raine Williams are midway through a circumnavigation aboard their J/40 Gryphon. When last seen, they were headed west from Australia.