Coupling between cycles of phytoplankton biomass and aerosol optical depth as derived from SeaWiFS time series in the Subantarctic Southern Ocean.

Abstract

The Subantarctic Southern Ocean is a high-nutrient low-chlorophyll region, and it has been suggested that primary production is limited by deep mixing and the availability of iron. Australian dust is high in iron content and can be transported over the Subantarctic Southern Ocean, particularly during the austral spring and summer when dust storm frequency in southern Australia is maximal. We present evidence for a coupling between satellite-derived (SeaWiFS) aerosol optical thickness and chlorophyll concentration in the upper ocean. The coupling is evident at monthly, weekly and daily timescales. Although the monthly coherence is likely to be due to other covarying factors, the coupling at weekly and daily timescales supports the hypothesis that the episodic atmospheric delivery of iron is stimulating phytoplankton growth. We also discuss the impact of oceanic dimethylsulfide production on aerosol concentration in the study region.