Melting Glaciers

There is a critical aspect of glaciers that melt that we rarely see in news reports. Yes, I do believe in Climate Change, but I do not have faith in “they should do something about it”.

Peru has lost more than half its water reserves as glaciers rapidly melt is an example. The article points out that the melt water often forms lagoons, but that these lagoons could overflow and flood areas downstream.

In the normal (hah!) course of events, some of a glacier’s ice will melt and form a stream of water that (normally) flows into a river and hence to the sea. In that sense there is little difference from rainfall in temperate areas. All part of the water cycle.

But water, like most materials, has phases – solid, liquid, gaseous – so think of a large block of ice at -20°. It sits there, and warm air or rain melts a little of it, which runs off, then more snow falls to replenish the block of ice.

Suppose now that the surrounding temperature creeps up and crosses the boundary line from below freezing to above freezing. That is, the temperature rises from -1c to +1c. The normal state of water at +1c is of course liquid form, and at that time, should the surrounding temperature remain above 0c, the block of ice will melt comparatively quickly and in its liquid form the water will flow away to the sea.

Crossing that boundary line from freezing to melting is a critical point, because suddenly the entire glacier can disappear. Really, as the surrounding temperature increases we see the glacier get eaten back towards its source.

But once the surrounding temperature crosses that boundary, and remains above that boundary temperature, the glacier is doomed. No matter how much snow falls naturally, it cannot replenish the glacier; the melting is far too rapid for snowfall to play catch-up.

It is the temperature of phase-change (zero degrees Celsius, 32 degrees Fahrenheit) that heralds a dangerous time.

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