Nitrate availability is generally considered to be the limiting factor for oceanic new production and this concept is central in our observational and modeling efforts. However, recent time-series observations off Bermuda and Hawaii indicate a significant removal of total dissolved inorganic carbon (C_T) in the absence of measurable nitrate. Here we estimate net carbon production in nitrate-depleted tropical and subtropical waters with temperatures higher than 20°C from the decrease in the salinity normalized C_T inventory within the surface mixed layer. This method yields a global value of 0.8 ± 0.3 petagrams of carbon per year (Pg C yr⁻¹, Pg = 10¹⁵ grams), which equates to a significant fraction (20–40%) of the recent estimates (2.0–4.2 Pg C yr⁻¹) of total new production in the tropical and subtropical oceans [ Emerson et al., 1997 ; Lee, 2001 ]. The remainder is presumably supported by upward flux of nutrients into the euphotic zone via eddy diffusion and turbulent mixing processes or lateral exchange. Our calculation provides the first global-scale estimate of net carbon production in the absence of measurable nitrate. We hypothesize that it is attributable to dinitrogen (N₂) fixing microorganisms, which can utilize the inexhaustible dissolved N₂ pool and thereby bypass nitrate limitation.