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.