Navigation in Ice.

There are many manuals and recommendations about navigating in serious ice, but here I want to present the less extreme conditions which still may wreak havoc on a small sailboat.

Growlers (Extremely Small Icebergs)

First danger come from small pieces of ice which are barely visible, especially with some wind around. They are called growlers. They may stick out only 5 or 10 cm. above water, but measure up to a meter in diameter (I assume that it is common knowledge that only 1/10th of the ice can be seen above water). And one meter of round ice is roughly 700 kilograms, so ramming it at 5 or 6 knots is definitively not a good idea for a fiberglass boat. So the recommendation is to navigate slowly (if you go 3 knots instead 6 knots, the damage will be only a quarter of that at full speed) and always to keep good look-out. Do not forget, the haste sank the Titanic. In my case, since the immediate area in front of the bow cannot be seen, I always make shallow S-turns to be 100 % certain that there are no surprises.

This video shows a growler. Note the color which makes it mimetize with the surrounding water. A growler 1/5th the size of that shown in the video can perfectly sink a fiberglass sailboat if rammed at sufficiently high speed.

Bergy Bits (Mini Icebergs)

Then, there are the bigger chunks some 1 to 6 meters high which are clearly visible. The problem with them is that they can suddenly disintegrate, with ice falling from top, or they can overturn, and a 2 meter high ice chunk may extend some 10 meters below, and when it flips, you well may become airborne... I felt that the best safety criteria was to have the top of the iceberg at an angle of less than about 20 degrees or 4 times its height. So if something sticks out 5 meters, you are OK if you are beyond 20 meters. In fact, I was very glad that I followed this rule because one three-story high chunk of ice fell off the iceberg. I was about 35 meters away and got splashed with the water.

This video shows the effects of a 10-meter piece of ice falling into the water some 35 meters away from the boat...
This piece of ice on the right is the one which fell off.
The rest of the iceberg after the fall.

The icebergs should be rounded on the windward side of the iceberg, because the ice debris which fall off the iceberg will float following the wind.

Underwater Icebergs Splitting from Glacier.

Next, there are the underwater icebergs at the front of the ice of the glacier. The glacier has a considerable part under water, and sometimes there may be an icefield under the water, and it may split off from under the water. The effects are eerie – it almost looks like a science fiction or horror film when some sharp chunk of ice slowly, taking several seconds, emerges from the water like a devils’ fang or worse… It is definitively not a good idea to try to approach the ice front of the glacier closer than 400 meters. The waves generated in such an event (of an iceberg emerging or ice falling from the top) can reach several meters, there is also the issue that when an chunk of ice falls from above, it may project water and smaller pieces of ice at a distance of more than 100 meters and considerable speeds. Getting a baseball-sized piece of ice at a speed of 100 kilometers per hour into one’s head is definitively not a good idea.

An underwater iceberg which split off and emerges from under the water in Laguna San Rafael.
Notice the projected water and ice bits which fly at least two times further than the height from which ice fell initially.


Finally, there is the danger of wind. The small icebergs can close in a boat very easily. There seems to be a safety built in into the glacier – when the global winds are relatively slow, there is a constant circulation of wind away from the glacier towards the lagoon. It is the same effect as the common shore breeze. The water temperature in the lagoon is around 7 to 8 degrees, and the ice is at best near 0 degrees, so that the “warmer” air above the lagoon rises and sucks the air from the glacier, and that generates the wind away from the glacier.

The ice usually falls from the glacier not in a constant way, but intermittently, i.e. at one moment a big chunk falls and generates a chain reaction which can last several minutes to a quarter of an hour when more and more chunks fall. Once the pressures are released the glacier calms down for an hour or even two, without any ice falls. Now, the ice which fell during such an episode slowly floats away from the glacier due to the action of this glacier breeze and forms a heavy barrier line which surrounds clear water close to the glacier. Sometimes it is difficult to penetrate this barrier, and in fact many small boats which bring tourists to the Lagoon do not dare or care to try to get closer to the glacier because of this line.

Finally, if there is a strong global wind, this can create a very dangerous situation and a boat can be easily and very quickly enclosed by the ice. So one always must keep an eye on the wind changes.

There is also the issue of sleeping during the night. A wind shift can bring grave consequences. So the best is to find a protected place. In case of Laguna San Rafael, there is one where Conaf has a small pierce, desembarcadero, which is about 3 miles to the north from glacier. It is in shallow waters 5 - 6 meters deep and in the west it is protected by a very shallow ridge, 1 to 3 meters deep which extends several hundred meters away from the shore, so that in case of a wind change most of the icebergs would be grounded on that ridge.