Fig. 5: Impact of SAM perturbations on the ocean.

a Shadings: norm of the ocean surface stress difference between the CTRL and SAM⁺ runs (i.e.,\(\parallel{{{{{{{{\boldsymbol{\tau }}}}}}}}}^{{{{{{{{{\rm{SAM}}}}}}}}}^{+}}-{{{{{{{{\boldsymbol{\tau }}}}}}}}}^{{{{{{{{\rm{CTRL}}}}}}}}}\parallel\)); the two colored contours indicate zonal surface stress sign changes (i.e. τ_u = 0) for both experiments; text boxes give each sector's average meridional shift in zonal stress direction change (in ^∘; positive values indicate southward shift). b Circum-Antarctic zonal mean of the zonal surface stress in the CTRL, SAM⁺ and SAM⁻ runs. The SAM\({}_{dyn}^{+}\) zonal mean surface stress response is identical to the SAM⁺ one, so it was not represented here. Colored vertical and horizontal lines, respectively, specify the latitudes of the southward shift of the mean zonal zero surface stress and the maximum westerly surface stress values. Here, “surface stress” is the total stress absorbed by the surface of the ocean, i.e. the combination of wind- and sea-ice-induced surface stresses weighted by the sea-ice concentration. c Map of the change in maximum vertical velocity (m s⁻¹, representative of upwelling) between the SAM⁺ run and the CTRL run. Hatching indicates non-significant changes at the 95% level and mean values (for the region located between the continental shelf break and 100 km north of the continental shelf break, delimited by the dotted lines) for each of the six regions shown in Fig. 1 are indicated inside white boxes. d Circum-Antarctic zonal mean maximum vertical velocity in the CTRL, SAM⁺ and SAM⁻ runs. The SAM\({}_{dyn}^{+}\) zonal mean vertical velocity response is similar to the SAM⁺ one, so it was not shown here. All values are time-averaged over years 25–29.