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Vanishing glaciers, and some that are hanging on

What a bad idea it was for some layout person at New Scientist to label the photo of a Himalayan glacier with the caption “Himalayan glaciers will vanish by 2035”. Putting “Some” before “Himalayan” would have made the story true, as opposed to false. Of course it would also have made the story boring, as opposed to attention-grabbing. That glaciers are vanishing is a commonplace of the journalists, and up to a point it is a truism.

But truisms need to be seen in true perspective. Some Himalayan glaciers have undoubtedly vanished already. When any regional inventory of glaciers is repeated, typically after a few decades, the count usually goes down slightly. Sometimes it goes up, if larger glaciers have fragmented into smaller ones. More often a few percent, or even just a fraction of a percent, of the glaciers have indeed vanished.

The true perspective on this is that the glaciers that have vanished were never very big in the first place. The last large-scale episode of glacier growth, the Little Ice Age, culminated 100—300 years ago depending on where you look. But wherever we look, the evidence is that nearly all glaciers have been shrinking since that time. It is likely that the ones that have vanished already are mostly the ones that came into existence during the few centuries leading up to the date of peak ice.

There is more to the true perspective, though. For a start, given the climatological evidence for warming, we need to know whether the rate of loss of ice is greater now than, say, a few decades ago. Here the glaciological evidence is unequivocal: it is. But there is still more to be said.

Plenty of small glaciers have failed to make it. South Africa lost its only glacier during the 1990s. Chacaltaya Glacier in Bolivia was highlighted as a disappearing glacier in volume II of the IPCC’s Fourth Assessment, where you can see it dwindling from 0.22 km2 in 1940 to 0.01 km2 in 2005. It disappeared in 2009.

On the other hand, some tiny glaciers have survived. Recently Grunewald and Scheithauer reported on those of southern Europe (excluding the Caucasus). It might be a challenge to identify in some of them the flow that is required by most definitions of the difference between a glacier and a snowpatch, but all are the genuine article in the sense that they are still there at the end of every summer.

I bet you didn’t know that there are two glacierets in Bulgaria. (I am betting on whether you knew, not whether you care.) The authors managed to retrieve ice cores from one of them, Snezhnika. It was 12 m thick at its thickest, and on average 3 m thick over an area of 0.01 km2, or 10,000 m2. Since the early-20th-century disappearance of Corral del Veleta in the Sierra Nevada of southern Spain, Snezhnika has been western Europe’s southernmost glacier, at 41.77° N. Working their way northwards, Grunewald and Scheithauer document glaciers in Albania, Montenegro (this one a monster, five times the size of Snezhnika) and Slovenia.

These shrimps seem to be doing OK, although the picture is mixed elsewhere. For example in the Cantabrian mountains of northwest Spain all that is now left of the Little Ice Age glacierets is four buried lumps of ice, while Calderone Glacier, in the Apennines of Italy, split in two during 2009.

All this might provoke subdued mirth among more macho glaciologists, but glaciers that refuse to go away should elicit admiration for their pluck and stubbornness. They also remind us that gains by snowfall and losses due to sunshine are not the whole story of glacier mass balance.

Chris de Beer and Martin Sharp studied 86 glaciers smaller than 0.4 km2 in southern British Columbia and showed that between 1951 and 2004 a few disappeared and a few shrank, but most didn’t change much. By careful analysis, they found that these objects have found sizes that are in equilibrium with their prevailing microclimates. Nearly all were in shadow for much of the time and were nourished significantly by snow avalanches from the surrounding terrain.

So the survivors offer a twist in the plot of the mass-balance story, but they do not point to flaws in our understanding of climatic change, and nor do the less fortunate ones. We should expect more and more disappearances as time passes, but should not panic when the journalists tell us that “Glaciers are vanishing”.

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