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HomeNL-2015-12 Coping with Cold Water


Coping with Cold Weather
1988
by
John Ohrt

With cold weather coming upon us, now is a good time for a reminder about special considerations for cold-weather paddling.  This article is re-printed from a 1988 HCC newsletter article, written by John Ohrt 27 years ago, but is still just as valid today.


 
The human body tries to maintain itself at a temperature of about 99°F. if the body gives up any heat to the environment it feels "cold". One way to look at the problem of being cold, is to think in terms of the presence or absence of heat. Cold is the name we give to the absence of heat, and to stay warm we must study the ways our bodies lose heat to the environment, and learn techniques to prevent this loss. Body heat is lost by radiation, convection, conduction, evaporation, and respiration.

Radiation is the loss of heat from a bare surface. This is the principle that explains why the coldest nights are the clear ones. Our unprotected bodies radiate heat into the environment, and this must be prevented by wearing insulating clothing. One area that is often overlooked is the head. The uncovered head can lose up to 1/2 of the body's total heat production at 40° (3/4 at 5°), so it is essential to carry and wear a warm hat in cold weather. One should even sleep with a hat on very cold nights for extra warmth. There is an outdoor saying, "
If your feet are cold, put on a hat". While I have never found this to be exactly true, it points out the idea that by preventing sizable heat loss from the head, you save that heat for other parts of the body. A warm hat should be standard equipment on any winter trip.

Convection is loss of heat from the body to moving air (wind). In the outdoors wind is one of your greatest enemies, quickly stealing body heat and energy. Our bodies warm a thin layer of air next to the skin, and it is a primary function of clothing to retain this warm layer of air. If wind constantly removes this warm layer, we feel cold. The extent of this can be seen on a wind chill chart. If the temperature is 40° with a 15 MPH wind, it is effectively 22°. This wind chill vastly increases if the body or clothing is wet. Being wet in a cold wind is a seriously dangerous situation that must be recognized and dealt with quickly. Windproof outer clothing protects against convection. Also one can use rocks, walls, bridge supports, and even canoes as wind breaks.
Do not underestimate the power of wind in accelerating heat loss, and do whatever you can to protect yourself in windy conditions.

Conduction is heat lost from direct contact with a cold surface ( rocks, metal, water, etc). An example of this would be sleeping without an insulating pad underneath you, which can feel as if your body heat is flowing directly into the cold ground. Because of this principle, it is best not to have direct, uninsulated contact with surfaces colder than your body. Another example would be a passenger sitting on the bottom of an aluminum
canoe. The direct contact with the cold water, through the metal, would cause this person to lose lots of heat quickly. Also, if your sleeping pad is not full length, make sure that your feet are up off the ground, or else they could become cold through conduction. Be aware and creative in insulating yourself from colder objects.

Waterchill is a particularly dangerous form of conduction, because the thermal conductivity of water is 240 times as great as that of still air. Water of 55° can extract heat from your body up to 240 times faster than 55° still air. This is why dry suits, wet suits, and pile or wool clothing are worn in cold water conditions, even if the air temperature is quite warm. Also be aware that clothing, especially down and cotton, loses insulating value when wet. Wool and synthetics are the clothing of choice for wet conditions. Be especially careful of any
situation that can combine wet clothing with a cold wind, as this can cause you to lose more heat than you can produce and lead to hypothermia.

Evaporation is heat loss from evaporation of sweat or moisture on the skin. This loss can be significant, but about all you can do about it is to adjust your pace to avoid excess perspiration. If you work too hard, you can produce too much sweat, which can soak your clothes and cause you to become chilled when you stop exercising. Take off clothes, open vents, and adjust your pace to prevent this from happening. In extremely
cold conditions, perspiration can condense and freeze in outer garments or sleeping bags causing them to become very heavy This principle can be reversed in the summer by pouring water over you and being cooled by the subsequent evaporation.

Respiration is the heat loss caused by inhaling cool air and exhaling warm air. There is not much you can do to prevent this type of heat loss. Breathing is not optional.

Remember that openings in clothing can lose a lot of heat, especially with the pumping motion caused by exercise. Buttoning the top button of your shirt, closing up zippers, and tucking in shirttails, can conserve a great deal of heat. The head and the back of the neck are also very vulnerable to cold, so wear a warm hat and turn up your shirt collar or wear a turtleneck or a scarf to protect these areas. Food is a source of energy and heat, so eat regularly and well; drink plenty of water also, to avoid dehydration. Don't overlook external heat sources such as fire and hot liquids. A quick fire can perk you right up on a chilly day, and a butane lighter, waterproof matches, and wax-paper for starter make a good fire kit. I have even seen flares used to start bankside fires. Hot liquids can be carried along in thermos bottles. A waterproof rain suit that can double as wind protection should be considered required equipment in the winter. Remember that shivering is the body's response to cold, and while it produces heat for the body, it also uses up a lot of energy and can wear you down to dangerous levels. Shivering

is a sign that you are too cold and need to warm up. Try to dress in several layers of loose clothing to trap insulating air; tight fitting clothes block blood supply and heat. Avoid cotton and rely on wool or synthetics for protection in cold, wet conditions.

Pay attention to the weather forecast, and take the necessary equipment, plus enough extra to handle a little worse weather than is expected This safety cushion should see you through any sudden weather shifts. You can always take clothes off, but you can't put them on if they're left at home or in the car. In Texas the winter weather can change dramatically; drops of 20° over two hours with high winds and hard ain are not uncommon. Go on trips prepared for the cold, and be alert to changing weather conditions and heat loss in yourself and your companions.
 
 


The author, John Ohrt.