VERTICAL FLUXES OF CARBON, NITROGEN, AND PHOSPHORUS IN THE NORTH PACIFIC SUBTROPICAL GYRE NEAR HAWAII

The hypothesized ''biological pump'' mechanism for removing carbon fro m the euphotic zone to the deep ocean requires different rates of recy cling of C, N, and P in sinking particles. At Station ALOHA in the sub tropical North Pacific Ocean (22 degrees 45' N, 1580 W), the C/N and C /P ratios in sinking particles increase with depth, while the ratios i n the upward mixing flux decrease. An exponential model of the sinking flux as a function of depth is used, which permits remineralization l ength and time scales (more properly called solubilization scales) to be estimated. Time scales (2-5 days) are consistent with microbiologic al decomposition, and length scales are greater for C (368 m) than for N and P (249 and 248 m), consistent with the existence of a biologica l pump for carbon. Assuming that the system is nutrient limited (total upward and downward fluxes of N or P are equal) permits us to estimat e vertical eddy diffusivity (K-Z) and the net export of carbon from th e system. Values of K-Z range from 5 x 10(-6) to 4 x 10(-5) m(2) s(-1) and are consistent with independent estimates for similar environment s. We estimate that approximately 20% of the air-to-sea carbon flux at Station ALOHA and a similar fraction of new carbon production are exp orted to the deep ocean (sigma(theta)>27) by particle sinking. Eddy di ffusivities are lower and net carbon export greater if phosphorus is a ssumed to be the controlling element. This has implications for the ro le of dinitrogen fixation in the subtropical North Pacific.