Particle export during the Southern Ocean Iron Experiment (SOFeX).

• Main Authors: K O Buesseler, J E Andrews, S Pike, M A Charette, L E Goldson, M A Brzezinski, V P Lance
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2005
• Subjects: Southern Ocean
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1078.5364; http://cafethorium.whoi.edu/TEXT/Buesseler%20et%20al%20SOFeX%20export%20L%26O%20Jan%2004%20submitted.pdf

ABSTRACT The impact of iron addition on particle export in the Southern Ocean was studied by measuring changes in the distribution of thorium-234, during a 4 week Fe enrichment experiment conducted in the high-silicate high-nitrate waters just south of the Southern ACC Front at 172.5°W. Decreases in 234 Th activity with time in the fertilized mixed layer (0-50m) exceeded those in unfertilized waters indicating enhanced export of 234 Th on sinking particles after Fe enrichment. The addition of Fe also impacted export below the fertilized patch by increasing the efficiency of particle export through the 100 m depth horizon. Extensive temporal and vertical sampling in a Lagrangian fashion, allowed for a detailed examination of the 234 Th flux model which was used to quantify the fluxes of particulate organic carbon (POC) and biogenic silica (bSiO 2 ). Iron addition increased the flux of both POC and bSiO 2 out of the mixed layer by about 300%. The flux at 100 m increased by more than 700% and 600% for POC and bSiO 2 , respectively. The absolute magnitude of the POC and bSiO 2 fluxes were not large relative to natural blooms at these latitudes, or to those found in association with the termination of blooms in other ocean regions. Evidence in support of Fe addition leading directly to significant particle export and sequestration of C in the deep ocean has proven difficult to obtain, however it remains a key question in the link between ocean Fe inputs and past changes in atmospheric CO 2 and climate. 4