Fig. 2.

Geochemical constraints on Fe limitation regime of the modern ocean. Simulated quantities from model Fe limitation scenarios are compared with observations (blue bars). (A) N budget of the Pacific Ocean: the basin-scale difference between N₂ fixation and denitrification (green dots) is balanced by a transport convergence of N* into the basin (red dots). Observational constraint applies to transport component, showing mean and SD of 10,000 Monte Carlo calculations of observed N* convergence into the Pacific (Fig. S4). (B) Difference in surface $\mathrm{P}*\left(\left[\mathrm{P}{\mathrm{O}}_4^{3-}\right]-\left[\mathrm{N}{\mathrm{O}}_3^{-}\right]/16\right)$ and (C) difference in thermocline $\mathrm{N}*\left(\left[\mathrm{N}{\mathrm{O}}_3^{-}\right]-16\left[\mathrm{P}{\mathrm{O}}_4^{3-}\right]\right)$ between North Pacific and North Atlantic Subtropical Gyres ($\Delta \mathrm{P}*={\mathrm{P}}_{\mathrm{NPSG}}*\mathrm{-}{\mathrm{P}}_{\mathrm{NASG}}*$; $\Delta \mathrm{N}*={\mathrm{N}}_{\mathrm{NASG}}*\mathrm{-}{\mathrm{N}}_{\mathrm{NPSG}}*$). Observed values are computed from World Ocean Atlas 2009 annual mean climatology with error envelopes representing SD between months in the monthly climatology. Arrow on B indicates observed P* difference between HOT and BATS locations. In all panels, simulated values and error envelopes represent mean and SD of four benthic denitrification scenarios for each Q_F/Q_O.