<p>Dissolved organic carbon is the largest reservoir of reduced carbon in the ocean but its sensitivity to climate change and consequent impacts on ocean biogeochemistry remain poorly understood. Here, we implement four dissolved organic carbon pools with the empirically-derived varying reactivities and lifetimes in an Earth system model to investigate their global distribution, impacts, and responses to climate change. The refractory pool, which has a lifetime of several thousand years, improves the model representations of low oxygen, high nutrient conditions in aged water masses. Under a high warming scenario, substantial decreases are projected across all dissolved organic carbon pools. This leads to a net conversion of organic to remineralised nutrients, which could have an effect on future changes in primary production. Under both weak and strong future warming, the model projects a long-term loss in the global dissolved organic carbon pool that is irreversible over centennial time scale, highlighting the need to sustain observations and improve model representations.</p>