While agreeing that it doesn't look a particularly brutish bird, to me it doesn't have the typical gentle look of an Iceland. My crude measurement (ruler on monitor!) is that it's also about 10% longer than the Herring Gull. Hence, my vote's for Glauc.
With lots of views, but only two previous comments, it would be interesting to know whether that's because everybody else agrees with Iceland, or is not sure?