> The implication is that you would ask the owners for permission to reproduce the image for the article.

Indeed. The origin of the image is the German Research Centre for Geosciences (GFZ Potsdam, http://icgem.gfz-potsdam.de/home) which has approved use of a very similar render under Creative Commons Attribution (cc-by) as noted in its wikipedia page: https://en.wikipedia.org/wiki/File:Geoid_undulation_10k_scal...

The source of this picture is their interactive renderer: http://icgem.gfz-potsdam.de/vis3d/longtime

The author of the blog post from the European Geosciences Union was at the time a postdoc at GFZ Potsdam.