Upwelling velocity and eddy diffusivity from 7Be measurements used to compare vertical nutrient flux to export POC flux in the Eastern Tropical South Pacific

•Mass balances of 7Be in the surface ocean were used to estimate upwelling velocity and eddy diffusivity.•Upwelling velocities were estimated to be 0.0 to 1.1 m d− 1 and Kz values ranged from 0.43 to 2.6 cm2 s− 1.•The vertical flux of NO3− across the base of the euphotic zone to be 0.15 to 3.0 mmol m− 2 d− 1.•We calculate that this input of NO3− would account for 1 to 19 mmol C m− 2 d-1 of new production.•Export estimates agree with this value along the 20°S, but along 10°S, export is 3-5 times less than new production.

Five 7Be profiles, measured in an area bounded by 10°S–20°S and 80°W–100°W, were used to determine upwelling velocity (wH) and vertical diffusivity (Kz). A positive correlation between wH and 14C primary production rate and a negative correlation between the inventories of 7Be and phosphate were observed. We interpret this as the influence of deeper, nutrient-rich, 7Be-poor water brought up by upwelling. Excluding two stations that appear to be influenced by non-steady state dynamics or horizontal transport, upwelling velocities were estimated to be 0 to 1.0 m d− 1 and Kz values ranged from 0.4 to 2.6 cm2 s− 1. From these parameters, NO3− fluxes into the euphotic zone were assessed and ranged from 0.15 to 2.9 mmol m− 2 d− 1. Using these values, we estimate 1.0 to 19 mmol C m− 2 d− 1 of new production in the ETSP. New production based on 7Be-derived transport parameters agree with carbon export estimates using a 234Th balance, sediment traps and O2/Ar supersaturation for stations along 20°S, but are higher than export estimates at 10°S, 100°W.