摘要：In this study we investigate the possible reasons for the widespread differences between the
seasonal cycles of carbon production and export compared to those of hypoxia in eastern
boundary upwelling systems. An idealized model is proposed that qualitatively
characterizes the relative roles of physics and biogeochemical fluxes. The model is tested on
three contrasting upwelling systems: the Benguela (from relatively aerated to
interannual anoxic), the Humboldt (sub-oxic and interannually anoxic) and the Cariaco
(permanently anoxic). Overall we propose that shelf hypoxia variability can be explained
on the basis of the interaction between ventilation by ocean boundary forcing
through ocean–shelf exchange and the role of shelf geometry in the retention
of shelf-based particulate organic carbon (POC) fluxes. We aim to identify the
hypoxia regimes associated with low ventilation—wide-shelf systems and high
ventilation—narrow-shelf systems, considering them as extremes of conditions controlled by
the two factors. We propose that this may help to explain differences in the seasonal
cycles of the biogeochemical drivers and responses as well as difference between
upwelling systems and within individual upwelling systems. It is suggested that when
seasonal hypoxia emerges it does so preferentially at a wide-shelf part of a system.
