Biospheric primary production during an ENSO transition

The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) provides global monthly measurements of both oceanic phytoplankton chlorophyll biomass and light h arvesting by land plants. These measurements allowed the comparison of simu ltaneous ocean and land net primary production (NPP) responses to a major E l Nino to La Nina transition. Between September 1997 and August 2000, biosp heric NPP varied by 6 petagrams of carbon per year (from 111 to 117 petagra ms of carbon per year). Increases in ocean NPP were pronounced in tropical regions where EL Nino-Southern Oscillation (ENSO) impacts on upwelling and nutrient availability were greatest. Globally, land NPP did not exhibit a c lear ENSO response, although regional changes were substantial.