Taxonomy is complex and unsettled. AOU and Clements/eBird retain a traditional arrangement of one species of Herring Gull. H&M4 and HBW split North American populations as a separate species, American or Arctic Herring Gull (L. smithsonianus). IOC further splits Vega/Siberian Gull (L. vegae) including Mongolian Gull citing Collinson et al. 2008, Yésou (Dutch Birding 24:271-298, 2002). Brazil (2009) further splits Mongolian Gull from Vega.
Regardless of taxonomy, this is an adult European type in full breeding plumage. Non-breeding plumage has the head streaked or mottled with gray. This is presumably the nominate race which breeds across Scandinavia. Note the pale eye with reddish orbital ring. Mantle color averages slightly darker than American Herring Gull. Canon SX50 HS PowerShot
References:
Brazil, M. (2009). Birds of East Asia. Princeton Univ. Press.
Collinson, J.M., Parkin, D.T., Knox, A.G., Sangster, G. & Svensson, L. (2008) Species boundaries in the Herring and Lesser Black-backed Gull complex. Brit. Birds 101(7): 340–363.
Burger, J., Gochfeld, M., Kirwan, G.M., Christie, D.A. & Garcia, E.F.J. (2018). European Herring Gull (Larus argentatus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/53982 on 27 August 2018).
Howell, S.N.G. and Dunn, J. (2007) A Reference Guide to the Gulls of the Americas. Peterson Field Guides, New York.
Malling Olsen, K. & Larsson, H. (2003) Gulls of Europe, Asia and North America. Christopher Helm, London.
Nisbet, I. C. T., D. V. Weseloh, C. E. Hebert, M. L. Mallory, A. F. Poole, J. C. Ellis, P. Pyle, and M. A. Patten (2017). Herring Gull (Larus argentatus), version 3.0. In The Birds of North America (P. G. Rodewald, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.hergul.03