Exploring Kootenay Lake

This is the month for star patterns to be seen in the ice of lakes and ponds. This is an early season phenomenon. When the ice becomes thicker, they can’t form.

I offered my first posting about these star patterns a year ago, at which time I discussed some misconceptions about their formation. Now, at the beginning of this season of lake-star formation, I discuss the sequence of events that causes them to form. 

When the freezing season begins, a thin layer of clear ice can form on ponds and along lakeshores. What is needed now is for the ice to be covered by some snow. However, the snow must be of uneven thickness, probably as a result of wind drift. Where the snow is thickest, it weighs down more on the ice and causes it to sink lower in the water than where the snow cover is thin. 

What happens now is a bit subtle. The water immediately under a flat surface of ice has a temperature of 0 °C. However, just below that, the temperature is +4 °C (which is actually denser water). Wherever the weight of snow has depressed the ice and pushed it down into that lower and warmer water, the ice immediately above it melts, and a hole forms in the ice. 

The overlying snow has yet another role to play in the formation of the star. Snow now wicks that warmer water up through the hole and onto the ice and this causes that warm water to flow up through the hole and to then radially percolate outwards to form stellar arms.

The lake stars in ice have formed. Later in the season, the greater thickness of ice doesn’t permit it, but for now, we see the patterns.

Stars appear in a pond, but the snow has largely melted.

And again.

On the surface of it, a title implying that a highway sign can both see and breathe is nonsense. Yet, when it comes to that breath, which is visible as a steam fog, there is a continuum. While the first three pictures were taken earlier, the final one of the road sign was taken yesterday.

On particularly cold mornings, people often can see their breath. That only means that in the moist air being exhaled, a cloud — steam fog — has formed. Water droplets condense when the water vapour from the lungs, with its high temperature and pressure, mixes with the external water vapour, with its much lower temperature and pressure. It is the mixing of these two markedly different packets of vapour that produces the steam fog that we refer to as seeing one’s breath. Here, an elk breathes warm vapour into the external cold.

However, an exhalation from the lungs into the external cold is not the only way to mix the contrasting amounts and temperatures of water vapour. Here a still warm October stream heats and moistens the air a few millimetres above it. This, then, becomes the equivalent of the moisture from the lungs as it mixes with the colder vapour above. A stream sees its breath?

One does not normally think of a wooden fence as a source of warm moisture, but this one had been wetted by an overnight dew. When warmed by the sun, a thin layer of warm (buoyant) moisture flowed up the side of the fence and, as it mixed with the surrounding colder moisture, it produced a plume of steam fog. A fence seeing its breath?

Finally, steam fog pours off of yestermorn’s road sign. As with the fence, the back of the sign had been moistened with dew overnight and was now warmed by the sun. The warm dew-covered sign was behaving the same way as the elk’s lungs.