Robotic observations of enhanced carbon biomass and export at 55°S during SOFeX

Autonomous floats profiling in high-nitrate low-silicate waters of the Southern Ocean observed carbon biomass variability and carbon exported to depths of 100 m during the 2002 Southern Ocean Iron Experiment (SOFeX) to detect the effects of iron fertilization of surface water there. Control and 'in-patch' measurements documented a greater than fourfold enhancement of carbon biomass in the iron-amended waters. Carbon export through 100 m increased two- to sixfold as the patch subducted below a front. The molar ratio of iron added to carbon exported ranged between [10.sup.4] and [10.sup.5]. The biomass buildup and export were much higher than expected for iron-amended low-silicate waters.
The Southern Ocean plays a critical role in the global carbon cycle and in the regulation of levels of atmospheric C[O.sub.2] (1-3), yet the biological and physical processes that sequester [...]