All Iñupiaq dialects have three basic vowel qualities: /a i u/. There is currently no instrumental work to determine what allophones may be linked to these vowels. All three vowels can be long or short, giving rise to a system of six phonemic vowels /a aː i iː u uː/. Long vowels are represented by double letters in the orthography: ⟨aa⟩, ⟨ii⟩, ⟨uu⟩. The following diphthongs occur: /ai ia au ua iu ui/. No more than two vowels occur in a sequence in Iñupiaq.