While phytoplankton play a key role in ocean biogeochemical cycles, the availability and supply pathways of resources that support their growth remain poorly constrained. Here, we show that the availability of various resources varies over several orders of magnitude throughout the Atlantic Ocean, causing regional contrasts in resource deficiency. Regional variations in the relative availability of nitrogen, phosphorous, silicon, iron, zinc, manganese, cobalt, and cadmium are important and result from the contrasts between winter mixing depths and differences in vertical profiles of the different resources. The winter‐time thickening of the mixed layer may replenish or deplete resources via entrainment, depending on the vertical nutrient profile. For nutrients like nitrate, phosphate, and cadmium, entrainment is a consistent source term. While for others, such as manganese and iron, entrainment can reduce ocean resource availability, particularly in subtropical regions. Any future change to the depth of winter‐time mixing will cause region‐specific changes in relative availability of different resources that may have important ecological consequences. Key Points There are large scale regimes present in mixed‐layer nutrient availability throughout the Atlantic Ocean Entrainment decreases the mixed layer availability of resources where the concentration decreases with depth Variations in nutrient availability and entrainment are linked to gradients in resource profiles combined with the depth of mixing