Regional differences in modelled net production and shallow remineralization in the North Atlantic subtropical gyre

Abstract

We used 5-yr concomitant data of tracer distribution\nfrom the BATS (Bermuda Time-series Study) and ESTOC\n(European Station for Time-Series in the Ocean, Canary\nIslands) sites to build a 1-D tracer model conservation\nincluding horizontal advection, and then compute net production\nand shallow remineralization rates for both sites.\nOur main goal was to verify if differences in these rates\nare consistent with the lower export rates of particulate organic\ncarbon observed at ESTOC. Net production rates computed\nbelow the mixed layer to 110m from April to December\nfor oxygen, dissolved inorganic carbon and nitrate\nat BATS (1.34±0.79 molO2 m?2, ?1.73±0.52 molCm?2\nand ?125±36 mmolNm?2) were slightly higher for oxygen\nand carbon compared to ESTOC (1.03±0.62 molO2 m?2,\n?1.42±0.30 molCm?2 and ?213±56 mmolNm?2), although\nthe differences were not statistically significant. Shallow\nremineralization rates between 110 and 250m computed\nat ESTOC (?3.9±1.0 molO2 m?2, 1.53±0.43 molCm?2\nand 38±155 mmolNm?2) were statistically higher for oxygen\ncompared to BATS (?1.81±0.37 molO2 m?2, 1.52±\n0.30 molCm?2 and 147±43 mmolNm?2). The lateral advective\nflux divergence of tracers, which was more significant\nat ESTOC, was responsible for the differences in estimated\noxygen remineralization rates between both stations.\nAccording to these results, the differences in net production\nand shallow remineralization cannot fully explain the differences\nin the flux of sinking organic matter observed between\nboth stations, suggesting an additional consumption of nonsinking\norganic matter at ESTOC.