Contribution of non-linear internal waves to marine net primary production has been underestimated

Field observations in the northern South China Sea (NSCS) indicate that elevated concentrations of chlorophyll a (Chl_a) associated with non-linear internal waves (NIWs) were more pronounced in the subsurface than at the sea-surface. At a given surface Chl_a, the vertically integrated Chl_a in an NIW-active area was 45% higher than that in an area where the NIW activities were minimal. As a result, net primary production (PPeu) estimated from surface Chl_a from remote sensing by using the current Chl_a-based PPeu model (e.g. VGPM) would have underestimated the true value by the same amount. If this correction is applied, the activities of NIWs would have elevated PPeu in the NSCS by 89%, rather than by 15–37% as previously reported. The elevated PPeu in the areas with high NIW activities would be at least 3.57 Tg-C yr− 1. It may account for 2.0% of new production in the South China Sea.