This species is famous for polymorphism. There is a continuum of variation from all dark to mostly white. Three subspecies are currently recognized although some (e.g. Howell 2012) question the validity of F. g. auduboni which ranges in the low arctic and boreal regions of the North Atlantic. F. g. auduboni is said to differ from nominate in that it occurs only in light morph and averages a longer bill. Both average larger than Pacific birds and have thicker bills and darker nostril tubes. Atlantic birds also have a paler less contrasting tail as seen here. I have tentatively assigned this individual to F. g. auduboni based on range and on the fact that only light morph birds were in the area.
An analysis of genetic and morphological divergences by Kerr & Dove (2013) recommended elevation of the Pacific subspecies F. g. rodgersii to full species. Flood & Fischer (2016) adopted this proposed classification. Canon SX50 HS PowerShot.
References:
Carboneras, C., Jutglar, F. & Kirwan, G.M. (2018). Northern Fulmar (Fulmarus glacialis). 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/52514 on 27 August 2018).
Flood B. and Fischer A. (2016) - North Atlantic Seabirds: Albatrosses and Fulmarine Petrels. Pelagic Birds & Birding Multimedia ID Guides, Scilly.
Howell, S. N. G. 2012. Petrels, albatrosses, and storm-petrels of North America: A photographic guide. Princeton: Princeton University Press.
Kerr K.C.R. and Dove C.J. (2013) - Delimiting shades of gray: phylogeography of the Northern Fulmar Fulmarus glacialis. Ecology & Evolution 3: 1915-1930. Published online 2013 May 22. https://doi.org/10.1002/ece3.597
Mallory, M. L., S. A. Hatch, and D. N. Nettleship (2012). Northern Fulmar (Fulmarus glacialis), version 2.0. In The Birds of North America (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.361