A coupled Biogeochemistry-Ecosystem-Circulation (BEC) ocean model is used to examine the sensitivity of ocean biogeochemical cycling and air-sea CO₂ exchange to variations in mineral dust deposition from the atmosphere.  Mineral dust deposition estimates from four different climate regimes are used to force the ocean model.  Our estimated climate-induced changes in dust deposition to the oceans significantly modify phytoplankton community composition, and global-scale rates of nitrogen fixation, export production, and air-sea CO₂ flux.  Dust driven variations in air-sea CO₂ exchange exceeding 1 PgC/yr are of similar magnitude to present net oceanic anthropogenic uptake.  Dust deposition directly modifies rates of export production and CO₂ flux over large regions where iron is the primary growth-limiting nutrient.  Dust deposition also indirectly influences these rates by modifying the rates of nitrogen fixation in the tropics and subtropics where nitrogen is the primary limiting nutrient.  Initially the direct pathway dominates the ocean biogeochemical response to dust variations, but over multi-decadal timescales the indirect response may be equally important.  Our predicted decrease in mineral dust deposition over the next century would significantly slow oceanic uptake of CO₂ and act as a positive feedback mechanism for the ongoing global warming.