Based on maps from the new Times Atlas, there are a number of reports in the news that Greenland has lost 15% of its 1999 ice area between 1999-2011: e.g. http://www.guardian.co.uk/
I’ve never worked on Greenland, so do not consider myself the best expert to ask on this topic, but glaciologist colleagues have been quick to point out that something funny has happened either in the mapping in the Atlas, or in the reporting of the Atlas map.
Glacier scientists on the glaciological listserve CRYOLIST pointed out that the brownish areas on the Times Atlas maps circulating on the web in fact contain glacierized areas, such as the mountain glaciers and ice caps peripheral to the ice sheet itself. Although these have been decreasing in area, the changes are not as large as the reported numbers and if one were to interpret all the brown shaded areas on the map as no longer ice-covered then it would be to say that all these mountain glaciers and ice caps peripheral to the ice sheet have disappeared, which they have not.
The National Snow and Ice Data Center (NSIDC) can illustrate this point quite well – and you can do this yourself by going to their website and visiting the Atlas of the Cryosphere, from where I developed the image below. In it the thickness of the Greenland ice sheet is presented in grades of pink and the outlines of other ice bodies in yellow. The data is plotted on the satellite image provided on the site for the month of July. Now, as the datasets are not from 2011, and do not include all of the mountain glaciers and ice caps surrounding Greenland, this is cannot be considered the current state of the ice extent (thats my clear disclaimer!), but it illustrates the point in terms of glaciological definitions of the ice sheet boundary versus other glaciers and ice caps that are not part of the ice sheet itself, and I decided that as it is from an online resource its worth posting as anyone can go and investigate this same data.
So the questions remaining are about whether the mapping is wrong, or the interpretation of the mapping is wrong so that we have ended up with misleading press releases.
(1) What exactly were the Times Atlas cartographers delimiting in their latest Greenland maps – i.e. what do they claim the brown areas are? To answer this, and therefore assess the work of the cartographers, we’d need to see a proper verison of the maps including the legends.
(2) On what basis is the Senior Publishing Editor for Collins World Atlases and The Times World Atlas seen in videos claiming a 15% reduction in the Greenland ice cap? Has he in fact interpreted the maps correctly? A technicality that not every layperson can be expected to know is that an ice cap is different from an ice sheet, but perhaps given his job he should be expected to know these things, and without this precision its difficult to what he is referring to? Does the map represent a more specific version than the 1999 one shown, in that it separates ice sheet (white) from other ice caps and glaciers in a different colour code (brownish), or is it a mistake in that all the glacierized areas outside the Greenland ice sheet have been excluded from the ice cover?
(3) The Guardian reported this as a 15% loss in permanent ice cover, but if that is the % change in the ‘white coloured area’ on the map, it is not the correct thing to do as there is a lot of ice within the brown coloured area too.
I’ll post better data on this later if I can, but now back to my own work
