Pumping of nutrients to ocean surface waters by the action of propagating planetary waves

Primary productivity in the oceans is limited by the lack of nutrients in s urface waters. These nutrients are mostly supplied from nutrient-rich subsu rface waters through upwelling and vertical mixing(1), but in the ocean gyr es these mechanisms do not fully account for the observed productivity(2). Recently, the upward pumping of nutrients, through the action of eddies, ha s been shown to account for the remainder of the primary productivity; howe ver, these were regional studies which focused on mesoscale (100-km-scale) eddies(3-6). Here we analyse remotely sensed chlorophyll and sea-surface-he ight data collected over two years and show that 1,000-km-scale planetary w aves, which propagate in a westward direction in the oceans, are associated with about 5 to 20% of the observed variability in chlorophyll concentrati on (after low-frequency and large-scale variations are removed from the dat a). Enhanced primary production is the likely explanation for this observat ion, and if that is the case, propagating disturbances introduce nutrients to surface waters on a global scale-similar to the nutrient pumping that oc curs within distinct eddies.