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Counting Glaciers

How many glaciers are there? For quite some time the standard estimate, offered in the 1990s by Mark Meier, was about 160,000. But when you dig a little deeper it becomes clear that there are probably a lot more than that. And of course the question connects with a closely-related question: Who cares how many glaciers there are?

The World Glacier Inventory is the place to go for a really long list of glaciers. The idea of listing the world’s glaciers originated more than 50 years ago with the Special Committee for the International Geophysical Year, which resolved in 1955 that “at the conclusion of the International Geophysical Year there be published as complete a list as possible of all known glaciers”.

I always like the definiteness and clarity of this directive. The International Geophysical Year ended in December 1958. The first recommendations about how to present the list of glaciers were published in 1959, in which year the first actual list, of some of the glaciers of Italy, also appeared. Since then, although there have been several ups and downs, the story has unfolded at about the pace with which it began.

Today the World Glacier Inventory exists as a computer database at the National Snow and Ice Data Center in Boulder, Colorado, containing records for just over 100,000 glaciers. I have made available a version, called WGI-XF, with records for 131,000 glaciers. If we kept counting glaciers at the average 1959-2009 rate, a little over 2,000 a year, we would have the Special Committee’ s complete list 15-30 years from now, only about 70 years late. By that time a fair proportion of the glaciers that were there in the 1950s will have disappeared.

Why so slow? Part of the problem is remoteness. Surprisingly, for some parts of the world there are still no maps of large enough scale to show individual glaciers. For others there are maps but they are closely-guarded military secrets, or are very hard to obtain, or are not accurate enough. Nowadays satellite imagery is making a big difference, but even with modern data sources we come up against the second big problem, which is that compiling a useful list of glaciers, even for a single region, is very time-consuming. To be useful, the list has to give not just a position but an outline or at least an area for each glacier, and preferably a good deal of other information as well.

The third major problem is money, combined with indifference. Apparently the more money you have, the less do you care how many glaciers you have. Bhutan has a complete inventory of its glaciers. There are 677. The two least complete national inventories are those of the United States and of my country, Canada. It is true that both of these countries have a great many glaciers, and therefore a lot of work to do, but this is what makes Mark Meier’s estimate of a total of 160,000 glaciers worldwide seem improbable. Guessing very roughly, there may be tens of thousands of unlisted glaciers in the U.S.A., and more than that in Canada. Add numbers like those to the 131,000 we have in hand, and speculate that there might be another 50-100,000 in the uncovered regions in the rest of the world, and you end up with an answer to the original question that has to be in the region of 300 to 500 thousand.

Who cares? I don’t think anybody actually cares about the count. It is the ancillary information for which glaciologists are hungry. For the study of global change, you can’t get a proper handle on glaciological change until you have a proper list of glaciers. You need to know, for example, how big each glacier was at some initial date before you can assess the significance of its size at a later date. The general picture is that all of them are smaller now, but that is an imprecise generalization. For informing policy in a responsible way we have to do better, if only because incomplete samples are vulnerable to the objection that they might be biased.

Posted by Graham Cogley on May 25, 2009 10:00 AM | Permalink