sˈɪns ˈæmsvɑːɹtnˌɪɹ ɪz ˈoʊnli mˈɛnʃənd ɪn dʒˈɪlfɐdʒˌɪnɪŋ, ɹˈuːdɑːlf sˈaɪmək θˈiəɹaɪzᵻz ðæt snˈɔɹi ɪnvˈɛntᵻd ðə lˈeɪk.
Since Amsvartnir is only mentioned in Gylfaginning, Rudolf Simek theorizes that Snorri invented the lake.