Tuesday, 21 April 2015

Overwintering in the ice in a small vessel


This post was originally written as a supplement to the Royal Cruising Club Pilotage Foundation / Imray publication Arctic and Northern Waters and so deals with the challenges of wintering in the Arctic. However almost everything is equally relevant to a vessel wintering in Antarctica. The chief exception is that there is little opportunity to ferry fuel to the winter site due to the distance of any part of Antarctica from the nearest source of supply. Another difference is that except for a few weeks in summer, all water will have to be melted from ice or snow. The extra fuel this requires must be allowed for.

The post is based on my experience gained during three polar winters on Iron Bark. One was alone in Antarctica, one in Greenland with Annie Hill and another in Greenland alone. Most of the information in this post can be gleaned from elsewhere in this blog or from the writing of a few other people who have spent a winter unsupported in polar latitudes. However I have not seen it summarised in a single article, so thought it worthwhile to do so.

It was possible to ferry fuel from a settlement to both winter sites in Greenland and on each occasion this amounted to about 1000 litres in total for cooking and heating. Ferrying fuel in Antarctica was impossible due to the long approach voyage in the Southern Ocean so I was limited to about 350 litres of fuel for all purposes. As a result Iron Bark was unheated in Antarctica for most of the winter; see Antarctica, Winter

Here is the original article.


Probably the best reason to spend a winter on a yacht in the Arctic is to see the full round of seasons, something that a vessel making a short summer dash to the north misses. Another reason is that ice conditions prevent a vessel completing its proposed voyage in a single season and the crew decides to spend the winter aboard and continue on the following year. A yacht that has decided in advance to spend a winter frozen in somewhere remote from a settlement can scout out a good location and perhaps ferry fuel from a settlement to the wintering site. However if caught by an early freeze-up, the choice of where to spend the winter is going to be limited to finding the safest cove in the vicinity with little chance of getting extra fuel supplies.  Either requires complete self-sufficiency for at least eight months. Wintering near a settlement is much simpler as food and fuel are available locally and help is at hand if the vessel is damaged or lost or if medical assistance is required. Having people around provides company through the long winter night, but at the cost of missing the experience of the remote, untouched icescape and its wildlife.

Many of the issues of choosing a site for the winter, preparing the boat, getting through the winter and breaking out of the ice at the end are similar whether near to or remote from a settlement. The rest of this section assumes the wintering site is remote, so some parts can be ignored if near a settlement.

The potential for crew problems when living in a cold, dark vessel through the winter should not be underestimated. Antarctic bases spend a great deal of effort screening numerous applicants for a few winter positions but still have a significant failure rate, and their living conditions are palatial compared to a yacht frozen in a remote bay. A single-hander is not going to have difficulties with crew but has to cope with whatever problems arise alone and may find the long, dark winter’s night hard on the mind. A larger crew on a bigger vessel has more comfort in the way of heat and light and people to solve any problems, but with a higher chance of conflict within the group. A couple who have lived and sailed together for long enough to be used to one another’s quirks is undoubtedly the best crew for such a venture.

Provisioning for an unsupported Arctic winter is different to provisioning in for an ocean passage. The minimum length of time between shopping opportunities will be about eight months and the amount of food required in the coldest months will be nearly double that usual in a warmer climate. Fresh vegetables, including potatoes and onions, turn to mush in the freeze-thaw cycles of autumn and few small boats can store enough refrigerated meat to last a year. This means the menu is going to be heavy on grains, pulses, legumes, rice and pasta and light on steaks, onions and potatoes. Vitamin supplements are a good idea, as is a well-stocked spice locker.

The menu will vary with personal taste, the size of the boat and how the food is stored, but some things are universal. It is going to cold, requiring as much as 5000 calories a day in mid-winter. A generous ration of carbohydrates and fats will give this. Rice, pasta, flour and oatmeal keep well and are easy to cook. There are many fats to choose from, but vegetable oil, butter and full cream powdered milk are a good start. If the use of tinned food is kept to a minimum but without resorting to dehydrated food, a winter ration will amount to about 1kg per person per day.

Cooking through an Arctic winter takes a lot of fuel as the ingredients are cold and appetites large. The amount of fuel will depend on the boat and on individual practice, but is likely to be about 120 litres of kerosene or the equivalent in propane per person, increased to 200 litres per person if it is necessary to melt ice or snow for water. If using propane, a kerosene backup stove is wise as propane stoves fail at –42°C. Butane is of no use at all as its boiling point is about 0°C. All diesel oil must be winter grade. Any summer grade fuel left in the tanks will gel to an unpumpable sludge during winter.

The pile of gear necessary to survive unsupported through an Arctic winter is considerable when added to food and fuel for cooking. It will include clothes, gloves, mittens and boots, long mooring lines with chain slings to secure to rocks ashore, shovel, pick, crowbar, ice auger, pitons, a sledge, snowshoes, tent, extra sleeping bags, candles and a comprehensive medical kit. Only a large vessel is likely to be able to stow all this and still be able to carry enough fuel to run a heater all winter. Given enough notice, a small vessel may be able to ferry fuel from a settlement to its wintering site, but finding suitable fuel containers in a small settlement can be a problem.

The ideal cove for a wintering site has an entrance only a little deeper than the vessel’s draft to keep out the bigger bits of drift ice, is small enough to run lines ashore to moor the vessel securely without aid of anchors and is surrounded by rocks to hold the winter ice place. It must be deep enough that it does not freeze to bottom as this will cause pressure ridging. The vessel should not be moored directly to a dock or rock face where it may be caught in the shear zone that develops between the floating bay ice and the fixed ice foot attached to the shore. If possible the bay will have interesting wildlife and scenery and a sunny southern outlook. The effects of flash flooding when ice dams up the valley burst in spring needs to be considered if a stream flows into the bay.

Having chosen the winter site, moor with lines ashore so that the vessel is head to the prevailing wind and retrieve the anchors. If an anchor chain is allowed to freeze in, the vessel may be towed out to sea by it when the ice breaks up. The mooring lines need to be kept from freezing in for the same reason. While the ice is thin, the mooring lines can be broken out by hauling a dinghy down them. Once the ice is thick enough to walk on, lifting the lines on top of the snow each day will stop them freezing in. The time between the beginning of freeze-up and being able to walk on the ice is more difficult. All that can be done is to stand on deck and flick the lines clear of the ice for as far as possible and similarly from the shore if it is accessible. The middle section of each line will freeze in and needs to be chipped out as soon as the ice is thick enough to walk on. The rope will be near the bottom of the newly formed ice and will remain there, sinking deeper as the ice thickens, so the sooner it is freed, the easier the job will be. If a rope is left frozen in, it will end up at the bottom of 1.5 or 2m of ice and will have to be cut when the ice breaks out, just when it is most needed.

Tracks in the snow made by walking along each line and pulling it up to prevent it from freezing in.

Once safely moored, the boat can be prepared for the winter. Exactly how the engine is laid up will depend on the installation. A keel-cooled engine with a dry exhaust requires nothing more than an adequate amount of anti-freeze in the coolant and can be run every week or two to keep the batteries full charged. A fully charged battery will not freeze and split its case. An engine with a heat exchanger and wet exhaust cannot be kept in commission once the cooling water inlet freezes and should be winterized by draining the heat exchanger, fogging oil into the cylinders and perhaps draining the block. The body of a seacock should be able to resist the pressure of water freezing in it, but using a dinghy pump to blow air through the line while closing the valve eliminates the problem entirely. Water tanks are best pumped dry before they freeze. Tanks freeze from the outside inwards so there is no problem in the autumn provided there is a small airspace to allow for expansion. However in the spring the tank melts from the outside, leaving in a large ice block surging around in the tank. This is noisy and detrimental to tank baffles and lining.

Poles marking a shore depot - the top of a fuel drum is just visible
It is prudent to have a depot ashore to retreat to if the boat is lost, fire being the chief hazard. The cache will need tents, food, stove, fuel and clothes to keep the crew alive for up to eight months, depending on how far the wintering site is from the nearest settlement. The depot needs to be marked by tall spars so it does not become lost under snowdrifts. Tents should not be erected lest they be damaged or lost in winter storms. The food should to be stored in containers strong enough to keep out an Arctic fox. A good quality plastic box will do. By repute, if there are bears or wolverines around, nothing will keep them out for long, but I have no personal experience with this.

Arctic foxes are common across much of the Arctic. They are inquisitive animals and soon accept a yacht and its crew as part of their landscape, especially if fed occasionally. Arctic foxes are omnivorous and will gratefully accept offerings such as porridge, rice, stew or mouldy eggs (which they always cache). They are timid little creatures that become confiding in time. Rabies is endemic in the Arctic and any fox acting aggressively towards humans should be strictly avoided.

A fox will probably adopt the boat. They are appealing but be cautious as rabies is endemic in the Arctic 

If it is not feasible to ferry fuel to the wintering site for some reason such as an early freeze-up, it will be necessary to do without heating for much of the winter. Living in a well insulated but unheated boat is not particularly difficult; certainly easier than it was for the Inuit who until recently spent their winters in relative comfort in snow houses heated by nothing more than a stone lamp burning seal oil. A small vessel with a snow cover is quite habitable even when heated by nothing more than a couple of candles and the intermittent use of the cooking stove. How habitable will depend on insulation, size of the boat and numerous other variables but the temperature will probably rise above freezing once the cooker and candles have been lit for the breakfast and stay there for most of the day.

All portholes and hatches except the main hatch need to be double-glazed. Temporary double-glazing can be made using acrylic sheeting screwed in place or even more simply and equally effectively from cling film plastic stretched across the opening. To conserve heat, decide how much of the boat is going to be lived in through the winter then bulkhead off the rest and let it freeze. The ends of the boat are the obvious areas to isolate. This is best done with purpose-made sheets of foam but an effective insulated barrier can be contrived using cushions from the cabins that are being closed off. The smaller the living area left, the warmer and more comfortable it will be.

Bulkhead off the ends of the boat and let them freeze. View looking aft from galley with the foam barrier removed.

Before letting a compartment freeze, open all its locker doors as it is difficult to do this without damage if they are allowed to freeze shut. If possible empty these lockers of everything that is likely to be required during the winter as it will be hard to do so once the locker is encased in ice. Equipment and supplies that will not fit in the warm section of the cabin are better stored ashore than left in the frozen sections of the boat. Cooking and breathing will produce enough condensation for everything in unheated part of the boat to be thickly encased in hard ice. Anything stored ashore will need to be dug out from under the snow but as it is in a dry environment, will not be frozen into a solid mass as it would be in the frozen ends of the yacht.

As a lead acid battery’s capacity drops quickly as the temperature falls, it is essential for the battery compartment to be heated if the domestic electrical system is kept in commission through the winter. Few small vessels can carry enough fuel to do this and also run an engine to generate power, leaving no option except to shut down the domestic electrical system for the winter. Candles and kerosene lamps give safe and reliable light together with some heat. Depending on latitude and thus the length of the polar night, 300 candles or 20 to 30 litres of lamp oil (kerosene) per person should do, varying with individual preference and tolerance to discomfort.

Candles vary dramatically in quality and it is worth trying a couple before buying a large quantity. The best burn all the way to bottom with a steady, nearly smokeless flame that does not vary in height and do not leave a puddle of wax behind. Puddled wax can be recycled by melting it into a shallow tin such as a small tuna can and burned using a wick made from a twist of toilet paper. A candles in proper holders is safer and more convenient than one stuck to a saucer or in a bottle. Even the best candles and most carefully trimmed lamp wicks eventually make the deckhead sooty, something that becomes obvious when the sun returns in the spring. Two candles or an oil lamp with a 25mm wick is usually enough to read by without strain, but eyes need more light as they get older.

Electric pumps and similar paraphernalia will of course be irrelevant for most of the winter so any essential for running the boat must have a manual backup. In fact no pumps except those used to transfer fuel are likely to work in midwinter. All critical systems must be able to run without electricity, which rules out Espacher-type heaters and Wabasco or Wallas types of cooking stoves unless they backed up by a system that does not need electric power. Preferred heaters are the drip fed type such as those made by Sigma, Reflecks or Dickinson. They require no electricity and, having no electronic components, can usually be repaired if they fail.

Good ventilation is critical. Ideally there will be a dedicated air supply led directly to the heater. In addition the cabin needs a permanent vent that keeps out drifting snow without restricting the flow of fresh air. Dorade vents are not likely to work unless they have cowls at least 60cm high to keep them above the snow.

Great care is needed on the installation of any generator set, especially regarding its air supply and exhaust system. This seems elementary, but has been the cause of a depressing number of incidents of carbon monoxide poisoning on boats in the Arctic. Candles are safer and as they dim and gutter long before the oxygen levels fall to levels critical for humans so giving early warning if the air supply becomes restricted. Unfortunately they do not give warning of accumulating carbon monoxide. 

As winter approaches, ice will form around the boat only to break out again in the next strong wind. Ice bumping around the hull is noisy and sometimes alarming, but rarely a serious problem. There is little point in wasting energy fending drifting ice off the boat with an ice pole as anything small enough to push away will not put any significant strain the hull or mooring lines. Ice snagging on the mooring lines is more of an issue as a rope stretching perhaps 100m to the shore can catch a lot of drifting ice, which puts it under great strain. Mooring lines can be partly cleared by flicking them over the drift ice nearest the boat. Ice caught on the mooring lines further from the boat can be cleared from a dinghy but this is difficult in strong winds, just when the problem is most acute. Using masthead halyards to lift the mooring lines above the ice generally causes more trouble than it saves.

As the ice thickens, getting ashore by dinghy becomes more difficult. Hauling a dinghy down a mooring line while chopping with an ice axe works for a while, but there will be a few days where the ice is too thick to break with a dinghy and too thin to walk on. When the ice is 75mm to 100mm thick, it will probably be strong enough to stay in place in a gale and should support a person’s weight. For the first few weeks when walking ashore on the ice, the intertidal zone ice will be thin and broken, requiring use of a dinghy either as a bridge or for a short ferry ride to cross it. Care is needed if using an inflatable dinghy for this as some, particularly the PVC type, become brittle and easily damaged at low temperatures.

It is worth building a snow cover over the vessel as soon as the ice will support one. The difference in comfort this makes is dramatic. Shovelling a pile of snow over the decks and around the hull works well, but in much of the Arctic there will not be enough snow on the ice to do this early in the winter. If the snow around the boat is scarce, it can be insulated by building a crude igloo with snow blocks cut from drifts ashore. Not all snowdrifts are sufficiently well packed for the blocks cut from them to be carried or sledded to the boat without crumbling. The Inuit can tell a drift’s suitability for building a snow house by plunging a stick into it, but the same information can be had by trial and error. A pruning saw makes a good snow knife and in summer is useful for cutting kelp off anchors. Alternatively a machete or something similar can be used. Building an arch of snow blocks over each porthole to let in light makes the boat a much more cheerful place.

A snow cover with openings over the portholes to let in light.

Cross section of a snow cover made of a combination of shovelled snow and cut snow blocks.

By mid winter all openings in the hull will be frozen shut rendering the toilet and galley sink useless. A stout bucket in the cockpit makes a good toilet with a similar one in the galley for slops. The contents of the toilet bucket will freeze solid in a very short time and can be emptied in down a tide crack, preferably a good distance from the boat. The best buckets for this are made of high density polyethylene (they have HDPE in the recycling information on the bucket’s bottom) as they do not become brittle at low temperatures. 

Streams continue flowing below the snow for a considerable part of the winter and getting water from them is simply matter of digging through the overlying snow towards the sound of the trickling water. HDPE buckets with clip-on lids are by far the best for collecting and carrying water. Jerry cans are slow to fill, allowing ice to build up around the top and preventing the cap from being screwed on. In cold weather, ice will completely block the neck before the can is full. Water buckets must of course be stored in the cabin to prevent them freezing solid.

After the streams freeze completely, probably in January, it will be necessary to dig a water hole in a lake. In midwinter a lake will have a variable thickness of snow over one to two metres of hard ice. The snow cover is no problem but digging a hole through the ice is hard, slow work. The minimum tools required are a shovel and pick, with a heavy crowbar and an ice auger highly desirable. A lanyard attached to an eye welded to the crowbar allows the crowbar to be retrieved if it slips through icy mittens into deep water. A water hole can be preserved for a couple of weeks by letting it freeze to a depth of 25mm or so then shovelling about a metre of snow over it for insulation. The next time water is needed, all that is necessary is to shovel the snow off and break through 100 or 150mm of ice. Eventually the bottom of the water hole, which is necessarily smaller than the top opening, will freeze shut and a new hole has to be dug.
A simple sledge is useful for hauling water

Digging for water and hauling it to the boat is hard work but the saving in fuel compared to melting ice or snow is considerable. Cooker fuel usage will nearly double if it is necessary to melt ice for water. The conventional wisdom that melting snow for water takes more fuel than melting ice is incorrect. Ice requires less attention to melt as the pot does not need filling nearly as often, but a pot kept full of compressed snow requires no more of fuel to produce a litre of water.

Dramatic photos like those of the crushing of Shackleton’s Endurance have lead to the expectation that any vessel in ice will be subject to pressure and forced upward. In fact the opposite is true. Provided the yacht is in a sheltered bay and protected from the pressure of drifting ice, it will be dragged down as the ice thickens. If the vessel is moored far enough from the shore to be clear of the shearing pressures of the tide crack and in deep enough water that the sea does not freeze to bottom and cause pressure ridging, there is little lateral pressure on the hull.

The sea ice thickens from the top by freezing seawater-saturated snow lying on the surface of the floe, so the oldest ice is at the bottom. Unless a yacht can emulate the Fram and withdraw its rudder, propeller any other underwater projections, these will become embedded in the first-formed, lowest ice and pull the boat down as the ice thickens. Fortunately it will not be pulled down by the full thickness of the ice. Initially the ice is thin and relatively weak so the vessel’s buoyancy will break the ice and it will float near its usual lines. As the ice is thickens and envelopes the propeller, rudder and other underwater appendages, the vessel will be dragged down until its buoyancy exerts enough pressure on the ice to allow it to rise a limited amount through the ice by pressure solution. Typically a yacht will be drawn down by 30 or 50 cm in the course of the winter, depending on the hull shape and depth of appendages.

Keeping the bow and stern clear of ice and turning the propeller regularly may stop the yacht from being drawn down at all, but breaking the ice under the flare of the hull is a miserable job. Ice has to be broken from the bottom of a pool of water while working in a kneeling position using a pick or crowbar and the ice fragments then scooped from the pool. Every stroke with the pick or crowbar sends up a shower of water that instantly freezes to clothes, mittens and the boat. It is an exercise best avoided.

Living in winter on a small vessel with marginal heating requires a little fortitude and much patience. The alcohol for preheating the kerosene stove will itself need preheating before it will burn, pens do not write and toothpaste will not squeeze from its tube until warmed in an inner pocket, butane lighters are useless, liquid detergent freezes and rum is a slushy solid. However these are merely time-consuming inconveniences, not real problems.

Thin polypropylene gloves are a great comfort working in a cold cabin and also make a good base under two layers of mittens for working outside. These gloves get grubby when working in the galley and wear out quickly, requiring frequent darning. At least ten pairs per person are a good idea.

A vessel with a pressurized hot water shower will find the system frozen for most of the winter and needs to make other arrangements for the crew to wash themselves. Less mechanized boats will probably already have a system that can be adapted to a cold environment. Simplest of all is to sponge bath in a large plastic tub. Alternatively a shower can be had using a sun shower suspended from the deckhead or using a pressurized garden spray. There must be a method of collecting the wastewater from these manual showers so it does not run into the bilges and freeze there.

Laundry is a nuisance but should not be neglected as dirty clothes quickly lose their insulation properties. It is easiest to carry the laundry to the water source and do it there but this is only possible down to –10°C. Below that clothes freeze to the side of the washing and rinsing buckets almost instantly and tear when pulled free. When that happens there is little option but to carry water to the boat and do the laundry there.
Doing the laundry beside a water hole in a frozen lake. This is only possible when the temperature is above -10°C. (Photo credit Annie Hill)

Drying clothes is equally problematic. There is an urban myth that clothes hung out in cold condition will dry by ‘shaking the ice out’. Nothing of the sort happens to anything more absorbent or tightly woven than nylon fishing net. At temperatures just below freezing, clothes will dry by sublimation when ice evaporates without going through a liquid phase. Sublimation slows as the temperature falls and is imperceptible below –10°C. At this point clothes have to come inside to dry, to the detriment of the cabin’s habitability.

Fortunately only the layers of clothes against the body gets grubby, so the only things that need to be washed on a regular basis are underclothes, gloves, socks and hats. Silk long underwear has much to recommend it as an inner layer, being comfortable and having less odour than polypropylene, but polypropylene is easier to wash and dry. A silk sleeping bag liner to protect the bedding is worthwhile and also saves a lot of washing. A coat dedicated for galley wear (or an apron) will protect other clothes from getting greasy and losing their insulation.

The length of the polar night depends on latitude. In most locations the sun will return before the coldest part of winter, which is usually in February. Despite this, with the return of the sun the hardest part of the winter is over. The joy the first sunlight brings is difficult to explain to anyone who has not spent a polar night isolated on a small vessel.

After sunrise, the days get quickly longer until the first drips of water on south facing rocks herald the approach of spring. Sometime in May it will be warm enough to clear the snow cover from the boat which shortly afterwards will float free of the ice with a narrow moat all around. The stern may still be held down because the rudder and perhaps the propeller are caught in the ice. This is hard on the rudder pintles and uncomfortable for living aboard. If the propeller is free of ice and can turn, running the engine in gear will send (relatively) warm water across the rudder and should eventually free it. If the propeller is not free or if it is likely to strike fast ice when the boat jumps up to float in its normal lines the ice will have to be broken away using a crowbar, pick and ice saw.

Once the boat is afloat, the toilet will pump out, the sink will drain and the water tanks can be refilled. As the hull warms up, the condensation frozen to the hull behind the linings and in the unheated bow and stern will begin to melt. The bilge pump suctions will still be frozen so there will be a period of several weeks during which this meltwater has to be bailed by hand. The amount will depend on the exhaust arrangements that were in place in the cabin and galley during the winter, but about 200 litres per person is likely.

Once the sea ice starts to puddle, the yacht needs to be converted back to being an ocean-going vessel in preparation for breaking out. The shore depot has to be brought aboard, sails bent on and hoisted, rigging checked, anchors and chains overhauled and machinery recommissioned.
 Sails dug out and hoisted to check them and the running gear prior to breakout.

Breaking out of the ice is potentially dangerous. Ideally the ice will melt around the boat and gently drift away as small, harmless pans. However a gale may send the ice out with a rush, buffeting the vessel on the way, or the bay ice may break out as a single large floe weighing thousands of tonnes with the boat still embedded in it in. Each situation will require a different solution and it is difficult to know in advance what it will be. All that can be done is have the dinghies ready to go, ice poles and spare lines to hand, anchors ready to run and the engine on standby.
Summer: this ice is rotten and about to break out.

The crew’s immune system will take a while to get working again after its winter-long germ-free holiday. Everyone will probably come down with a respiratory infection when they first make contact with the outside world. Not much can be done about that other than to allow a few days for recovery before continuing with the new season’s venture.


  1. best info online, hard to find info for wintering aboard, looking forwards to next blog.
    cory eastern ontario canada

  2. Best information I have seen on this subject. Forty two years ago I did a trip with HW Tilman and he spoke of his long standing wish to over winter in high latitudes, but he never got round to doing it.

  3. Fascinating account of your experience. No doubt that your 3 trips were amazing endeavors! Just a caution to your readers regarding animals; rabies is 100% fatal unless treated, and can be transmitted by saliva not just a bite. Had a friend bitten by a wild dog overseas, completely unprovoked and without warning.

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