In winter, the temperature moves smoothly from + to – . A lot of energy has to be extracted for the transition from water to ice. Nature contains a lot of water. Why then is there no discontinuity?

You are of course right. Your idea is correct in that the transition from ice to water is indeed a process that requires a lot of external heat.

However, there is a phenomenon that somewhat counteracts what you are describing.

Warming up air requires very little heat, and what’s more, the kind of weather change you describe is often the result of a layer of warm or cold air blowing over us from somewhere else.

If we allowed everything to come to a perfect balance, you would indeed see a stagnant temperature for a while, but since heat transfer between ice/water and the air is very slow, we see the (air) temperature making all kinds of jumps, while the water, that has to lose all its heat to the air (or ice that has to absorb all the heat to melt from the air) is a few days behind.

Anyone who sweeps up a large pile of snow will also notice that it is still there three days after all the other snow has melted, and that it is still neatly 0 degrees, even if spring has started in full force in the meantime.

The same applies to ice on ponds and streams – it takes weeks of freezing before people in the Netherlands think that enough ice has formed for an Eleven Cities Tour. And if spring suddenly sets in, that ice will certainly remain for a few days.

So the answer to your question is – the discontinuity does indeed exist at the local level (in a layer of snow or your pond), but in general the heat transfer between ice or water and the air is too low to affect our environment, and certainly the air, to achieve a homogeneous temperature.

The effect does play globally, of course, which is exactly why a maritime climate has much milder winters and cooler summers – often the wind blows from the sea, where the air has had a lot of time to absorb heat or give it to the water, and the temperature extremes are thus damped. In Siberia, which does not have such a water buffer, temperatures can reach 40°C in summer and -40°C in winter

Kind regards,

Christophe Vandevelde