Decreasing iron stress may enhance the deepening of the phosphacline relative to the nitracline through stimulation of nitrogen fixation. . In CESM2, we adjusted iron stress by increasing 5 atmospheric iron deposition (DFe) rates either by hemisphere or globally (Fig. ). Increased deposition rates increased nitrogen fixation and resulted in a faster deepening of the phosphacline relative to the nitracline (Fig. ). We again found a significant relationship between the residual TPO4 and integrated nitrogen fixation (slope = 7 x 10 -4 m x [Tg Nfix] -1 , slope SE = 2 x 10 -4 m x [Tg Nfix] -1 , p = 3 x 10 -3 , n = 10). Additionally, we determined nutricline trends in regions with 10 different primary nutrient limitations (Fig. ). Increased DFe led to a faster deepening of the phosphacline relative to the nitracline no matter the location, but the strongest effect was in ironlimited regions. This suggested that as iron stress was alleviated, it was eventually replaced with increased phosphorus stress. Thus, an increase in nitrogen fixation by alleviating iron stress directly results in a faster deepening of the phosphacline relative to the nitracline.