Tag Archive for: glaciers

I have received an incredible amount of very positive feedback about my recent essay, and it motivated me to address some of the questions that came up both in direct response to it and in other discussions.

This article is intended primarily for visitors who are concerned about various planned activities, and deals specifically with the situation in Iceland. A discussion detailed enough to satisfy glaciologists and outdoor professionals is clearly outside the scope of a simple blog post!

What makes ice cave tours different from other glacier excursions, such as glacier hikes or ice climbing? Or are they all equally dangerous?

The answer, as one would expect, is complicated and depends on many factors. One could (and possibly should!) write an entire book on the subject, but we can certainly examine some general aspects. Here I will focus on the glacier itself, and particularly on the areas most commonly visited for tourism activities, which are snow free in the summer months (the ablation zone).

Let us begin by examining how a glacier evolves throughout the seasons. In summer, the glacier is exposed to near 24 hour daylight, warm temperatures and rainfall. This deteriorates the upper layers of the glacier in a way commonly called sunbaking – essentially each of the individual crystals melt along their boundaries until they entirely lose adhesion and become what is perhaps best described as a brittle set of loose puzzle pieces. Importantly, this does not only happen at the surface, but because the sunlight penetrates into the ice also progressively occurs into greater depths forming a layer that is called the weathering crust. This means that as this process continues throughout the summer, the glacier not only melts at the surface but also deteriorates internally, while at the same time loose fragments on the surface get entirely eroded away or dislodged by gravity, surface water, or other effects. Surface water also continually seeps into surface defects and can further affect the ice in ways not easily observed from the outside.

There are noteworthy exceptions, of course. For example, any glacier that is covered with substantial amounts of debris (such as volcanic ash in the case of Kötlujökull) may be protected from much of this effect and exhibit slower rates of change.

In winter, the glacier is either protected by snow cover (which entirely stops erosion) or is exposed to very little sunlight – this causes the weathering of the glacier in the winter months to primarily occur at the surface level, leading to the highly polished, smooth and glass hard winter ice.

With these basic processes in mind, we can now examine their consequences for various types of excursions on the glacier.

Surface Activities

Consequently, if a glacier activity remains on the surface of the ice (such as a glacier hike), the loose and relatively soft summer ice is in many ways preferable. There is great traction with crampons, and the roughness of the sun baked crystals means that a person that fell down would just remain put in most normal terrain – although they may cut their hands on the sharp edges if not wearing gloves. Any degradation of the ice into greater depths is not a concern since we will generally walk on top of many meters of ice that is at no risk of collapse under our weight, and it is still very strong under the negligible compression of our body weight. Loose ice can be easily removed to access solid, blue ice underneath for building reliable climbing anchors.

In contrast, winter ice can be so hard that especially lightweight clients will have a difficult time finding good purchase with their crampons. The exposed ice is much harder, and even if the crampons have been sharpened to a sharp point do not penetrate very well. A stumble may quickly lead to a slide that is very difficult to recover from – so even otherwise very benign terrain may need to be protected.

A light snow cover greatly diminishes this risk once it has bound with the ice underneath. However, a more substantial layer of snow causes traveling over the glacier to become more hazardous, because windswept snow can easily obscure any dangerous spots in the surface. Larger moulins are likely to remain somewhat visible, but even a misstep into a smaller void underneath the snow could easily result in a sprained ankle, knee injury or other harm.

To protect from these fall hazards, good route choice and the use of fixed or temporary ropes are generally sufficient and easily managed.

Overhead Hazards

Once we are exposed to any overhead hazards, the picture changes. In the summer, we routinely see smaller fragments coming loose under their own weight and harmlessly tumbling down surprisingly moderate slopes, and if the structure becomes steeper the chances of larger pieces breaking off increases dramatically. In particular, if a feature is free standing (such as an isolated wall) the sun baking may occur from multiple directions until there is no core with good integrity left.

We also need to keep in mind that while ice is very strong in compression, even in its compact form it is quite weak in tension, and any ice affected by sunbaking will exhibit dramatically lower tensile strength yet! We must therefore rely on any overhead features to be well supported on both sides, having a good, self supporting shape, and suitable thickness.

Whether we encounter those overhead hazards on a normal glacier hike (maybe walking a bit into an accessible crevasse, like routinely done on Falljökull, or into a moulin as it has been popular on Breiðamerkurjökull), because we are suspended from a rope and climbing up a vertical wall, or going into an ice cave does not necessarily change the character of the hazard.

What does change however is how long we are exposed to the risk, and if that particular location is an essential component of the tour program or can be easily avoided.

On a glacier hike the guide can always choose to not approach any vertical or overhanging terrain at all, or if it cannot be avoided mitigate the risk by limiting the duration of the exposure (very much in the same way one would pass through a potential rockfall area without stopping).

For ice climbing, we must indeed be in sufficiently steep terrain that allows the client to learn good ice climbing technique and gives a good experience – but since essentially all commercial ice climbing tours are top rope scenarios, loose material can be easily managed from above before the client proceeds to climb.

Therefore, for both glacier hikes and ice climbing, approaching and inspecting the overhead feature closely is generally possible without much additional effort, and allows for good and timely judgment of its condition.

With ice caves, the whole premise of the tour is to spend the majority of the duration exploring areas underneath the surface, and thus the overhead hazard is continually present or at least cannot be avoided when entering and leaving the area. Space is often limited and there is not enough room to avoid prolonged exposure overhead hazards. In a sufficiently large cave, the inner sections are often covered with sufficiently thick and homogenous ice that a collapse is unlikely – although there have been exceptions with pieces of the otherwise stable roof flaking off, icicles forming overhead, embedded rocks threatening to melt loose, etc. Furthermore, inspecting many of those overhead features in detail is generally more difficult, if at all possible, more time consuming, usually requires leaving the group temporarily unattended, and may therefore be limited to infrequent checks. Those may be sufficient in the winter months, when the rate of change is generally relatively slow, but becomes extremely problematic during the summer.

Other Risks

Of course, the integrity of the ice is not our only concern on glacier excursions. Common to all activities is that there is generally no easily accessible shelter from severe weather (except in larger ice caves, which can remain surprisingly comfortable even if there is a raging snow storm on the outside).

Also common to all glacier activities is that most clients are unfamiliar with the use of crampons, and the risk of self injury or stumbling certainly needs to be considered. Ice axes and ice climbing tools further increase this risk, especially when used or carried incorrectly.

Particular to ice climbing, protective eyewear is important to prevent injury from ice spray and clients with poor technique are at a considerable risk of hitting their knuckles when placing the ice tools. Bystanders, including the guide if belaying from below, are at risk of being hit by ice dislodged by the climber. And clearly the proper use of all safety equipment and good belaying technique are critical to ensure a potential fall of the client is caught safely. Warm temperatures and sunbaking require the rope anchors to be carefully planning and constructed, protected from unnecessary deterioration, and may need to be checked frequently. Ice screws have high thermal conductivity and may melt the ice surrounding them, becoming loose over a relatively short time if ambient temperatures are high. This is less of a concern in the winter months.

Ice caves are generally formed by subglacial water flows or geothermal activity. Those water flows generally subside in the winter when both meltwater and rain are diminished, but especially during warm spells and spring can increase dramatically. Water held back by the glacier in subglacial or marginal lakes may spontaneously drain as a jökulhlaup that could reach into ice caves or the proglacial area around the cave. A warm spell and rain falling onto snow cover can release substantial slush flows that might drain into exposed areas such as moulins. Geothermally formed ice caves, if poorly ventilated, can accumulate high levels of toxic gases, or reduce oxygen concentration with inert gases to dangerous levels.

Finally, sloppy or poorly maintained safety precautions can substantially increase risks. A rope, handrail or bridge will be trusted by customers to be reliable and trustworthy. On a warm, rainy day it may take only a few hours until an ice screw melts loose enough to be dislodged with minimal force, and while V threads generally last longer they too eventually melt out. In both cases whoever was pulling on the rope to keep their balance will have a very nasty surprise. Poorly tied knows may come undone with catastrophic results. Ropes left to freeze onto the ice may snap loose once a client pulls on it, throwing them off balance. In all of these cases, it might have been safer if there were no rope in place at all!

Putting it all together

In summary, one could very generally say that –

• Glacier hikes are safest in the summer, and some additional risks must be managed in the winter months.
• Ice climbing is generally somewhat more dangerous due to the use of additional, very sharp tools, necessary exposure to heights and general character of the activity. While overall easier in the summer months, care must be taken to build reliable anchor structures and reduce the risk from falling debris to the climber and any bystanders.
• Ice caves are safest in the winter, when the cold temperatures and limited sunlight allow the ice to remain relatively stable. There is a very high risk both in the spring when snowmelt and slush flows must be expected, and later in the summer once the deterioration through sunbaking penetrates any overhead ice structures to dangerous levels. The most dramatic changes haven often been observed from mid August until early October.

While both glacier hikes and ice climbing occur in environments that are more easily managed, and there generally is a much larger range of options to choose from, ice caves are dramatically more limited in number and allow fewer alternatives for risk mitigation or avoidance.

There have certainly been years where exceptional conditions allowed ice caves to be visited earlier than normal, later into the spring, or perhaps even in mid summer, but we must be careful to ensure that such an exception does not continually become the new norm due to outside pressure or expectations.

Ultimately, glaciers are a rapidly changeable environment. Safety plans, regular site evaluations and standard practices are all valuable tools but cannot replace a well trained guide who is able to competently assess the situation in the moment, and also has the authority to make possibly drastic decisions about any tour. This requires training, experience, and a supportive work environment.

This unpredictability is why almost all guide companies will not generally offer ice cave tours outside of a time frame where experience over the past decades has shown that visiting them can be performed in a safe fashion, and even within the winter months sometimes must be canceled.