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Abstract:
Three Carbon Explorer (CE) floats profiling to kilometer depths in the Southern Ocean tracked
dawn-dusk variations of mixing/stratification, particulate organic carbon (POC), and light scat25
tering and sedimentation at 100, 250, and 800 m continuously from January 2002 to April 2003.
Data were analyzed in conjunction with contemporaneous satellite winds and chlorophyll and
derived subsurface light fields. The CE deployed at 66°S 172°W operated in the ice edge zone in
absence of light. Two CEs deployed at 55°S 172°W recorded wintertime mixing to ~400 m, yet
observed very different bloom dynamics and sedimentation the following spring. Four hypothe30
ses are explored. The strongest is that shallow transient stratification of the deep winter mixed
layer to shallower than photosynthetic critical depth occurred more frequently in the non-bloom /
higher sedimentation case. The lower particle export to 800 m under the bloom was hypothesized to be due to higher interception of sinking carbon by a relatively starved over wintering zooplankton population. In the Southern Ocean surface phytoplankton biomass may counter in35
dicate particle flux at kilometer depths.