A Matlab datafile named S1_Data is provided as supporting information.

This file contains the following two data structures: Lefort_et_al = O2: [821x377 double] x: [1x822 double] z: [1x377 double] Bourgault_Cyr = O2: [826x201 double] x: [1x826 double] z: [1x201 double] where the structures Lefort_et_al and Bourgault_Cyr contain, respectively, the Lefort et al. (2012) [2] model results (Fig 1a) and the new results presented here (Fig 1b). Each structure contains the oxygen concentration field .O2 (mmol m-3), the along-channel axis .x (m) and the vertical axis .z (m). Lefort_et_al = O2: [821x377 double] x: [1x822 double] z: [1x377 double] O2: [821x377 double] x: [1x822 double] z: [1x377 double] Bourgault_Cyr = O2: [826x201 double] x: [1x826 double] z: [1x201 double] O2: [826x201 double] x: [1x826 double] z: [1x201 double] (MAT)