Articles - Winter Climbing Skills - Part 1: Judging Weather Hazards.
Photo: Glenmore Lodge
by George McEwan - Glenmore Lodge
Winter Hazards Test
Scotland’s winter weather is extreme and unpredictable. When it’s bad it compares with any arctic storm, and can be just as lethal. Yet on other days, when not a breath of wind disturbs the snow, blue skies stretch endlessly overhead and the sun is shining it can be difficult to imagine that only yesterday you were working hard just to survive.
Some of the ingredients that make climbing in winter that bit spicier are short daylight hours, poor weather, avalanche risk, cornices and winter medical conditions such as frostbite and hypothermia.
Scotland’s wildly variable weather is the key element in determining the unique and extremely variable climbing conditions we get. One minute we can be wallowing in slush, then several hours later, as an arctic front passes through, the same slush can very quickly freeze to iron-hard névé. Yet it can also work the other way. Its possible to be climbing a route only to have the ideal mixed climbing conditions melt out to the extent that by the time you reach the top, the whole climb has been stripped of its snow cover. What was once pristine white rimed-up rock is now dripping wet. It is this unpredictable variability that makes mountain weather such a key to success, or failure, on any climbing trip.
On Cairngorm summit the average wind speed through the winter months is around 35mph, but wind speeds in the range 60 – 80mph for long periods are not uncommon.
Strong winds combined with falling, or wind eroded snow, produce a winning winter phenomena, the white-out. In a white-out all sense of up, down, steepness etc just disappears. Your world, in this sensory deprived environment, is limited to little more than an arm’s length in front of you. Add to this the following:
Avalanche and Cornice
The strong snow-bearing winds that were buffeting our two climbers in the opening paragraph can produce one of the most common avalanche phenomena in the mountains – windslab. Windslab builds up on lee slope i.e. the side sheltered from the wind.
Another result of this snow bearing wind is cornice formation. Cornices occur when the same snow-bearing wind blows over a steep lee slope creating an overhanging snow build-up. Cornice development is more likely within the wind speed range of 15 – 45mph. At such comparatively low wind speeds the snow crystals attach themselves to the existing snow pack and resist further removal thereby creating a cornice built from soft packed snow . An eddy is created where the snow circulates with the up-draught building the ‘roof’ of the cornice. A newly-formed cornice should be treated with caution: at this stage it is still unstable and collapse can be spontaneous or victim-triggered e.g. as a climber attempts to climb over or through it.
The eddy also deposits windslab on the slope (known as the scarp) directly underneath the cornice. Many climbers have come to grief on this section by triggering the slab as they attempt to access the cornice.
Only after a period of thaw/freeze (where the freezing level rises and falls thereby stabilising the snow pack) do cornices become more stable. Ben Nevis at the end of the season can sport some fantastically huge cornice features that, having gone through so many thaw/freeze cycles, are more ice than snow. When there is a big thaw e.g. heavy rain or the freezing level is above the summit, watch out for cornice collapse. Tell tale signs are the cornice slumping and drooping over the gully, with water dripping off it.
TOP TIP Avoid cornices if you can! At the top of gullies there is often a bowl, above which cornices will build, given a particular wind direction. You may be able to outflank the cornice by moving out onto one of the crests formed by the sides of the bowl. You’ll usually find some wind-scoured snow here which will allow easier access up or down. If descending you can always set-up an abseil using a snow bollard (see Winter Belays).
Hypothermia is an insidious medical condition that can affect all winter climbers. In fact you will almost certainly have been hypothermic at some time when you have been out on the hill. Hypothermia results when the core temperature of the body drops below 37ºC (i.e. the human body’s normal temperature). When your core temperature drops to around 36ºC you will start to shiver, as the body attempts to stimulate heat by muscle effort. Another symptom, but more subtle and potentially more lethal, is that our capacity to make judgements is reduced. A short slide down to just above 35ºC sees apathy and confusion set in.
Put these physiological responses into a climbing situation and you can quickly see the huge scope for disaster developing. Navigation errors become more likely, you may not be bothered to stop and change your gloves, letting your hands start to freeze, limiting your dexterity and thus your ability to open your rucksack to put on some extra clothing, maybe eat some more food. Not taking time to look after yourself sets up a spiral of decline. If you do not sort yourself out and your core temperature continues to drop to around 30ºC you will stop shivering and will start to lapse into unconsciousness. Not that you will be aware this is happening, you’ll be so out of it by this stage you will not realise you are dying.
Stop this spiral of decline early on. Mild hypothermia is very easy to deal with. Basically you can reduce the cold challenge by putting on a hat (we lose around a third of our body heat from our heads), pull on your belay jacket and get some high energy food into you. If you do not deal with the problem early on, and wait till someone is dropping onto the ground then the situation literally becomes one of life and death which will require specialist rescue help.
Frostnip (actually superficial frostbite) is also fairly common. Especially if you are walking/climbing in very strong cold winds. The commonly affected areas tend to be the exposed sections of the face e.g. nose and cheeks. To avoid this ensure your face is well covered up e.g. wear a neoprene ski mask. Failing that ensure you and your buddy keep an eye on each other’s faces. Frostnip affected tissue can be recognised by it being numb, and white or waxy in appearance.
Frostbite is a far more serious condition, although it tends to be relatively rare in this country due to our wetter, warmer winter climate. Some of the key signs to look for are:
- the affected body part (commonly in climbers the fingers or toes) will lose sensation and feel numb
- flesh will appear hard to the touch and the skin will be white and waxy.
Don’t be tempted to thaw the affected part out, protect it from further freezing, and seek urgent medical help.
How to avoid the deep freeze
The main factors that can lead to hypothermia are: low temperatures, wind-chill, wet conditions, inadequate diet, the climber’s morale, and exhaustion. Exposure to any or all of these factors can lead to the onset of hypothermia and pre-dispose the mountaineer to making potentially fatal mistakes. Preventing heat loss can be dealt with by being adequately prepared mentally, physically, and technically. So ensuring your personal clothing and equipment is up to the task is extremely important.