ɹˈɪvɚɹ ˈɔːfeɪz fˈɔːɹm wɛn ðə kɹˈɔssˈɛkʃənəl ˈɛɹiə əvə stɹˈiːm tʃˈænəl bɪkˌʌmz lˈoʊkəli ɹᵻstɹˈɪktᵻd æz ˈaɪs ɐkjˈuːmjʊlˌeɪts dˈʊɹɹɪŋ wˈɪntɚ.
River aufeis form when the cross-sectional area of a stream channel becomes locally restricted as ice accumulates during winter.