Biophysical coupling in remotely-sensed wind stress, sea surface temperature, sea ice and chlorophyll concentrations in the South Indian Ocean

Satellite records of chlorophyll, sea-surface temperature, sea-ice concentration and wind-stress curl, together with reanalysis wind fields, have been analysed to identify connections between the physical environment and phytoplankton growth. The study focusses on the BROKE-West survey region in the Indian Ocean sector of the Southern Ocean: 20° to 90°E, 70° to 50°S. Correlation and regression analyses showed that, of the parameters that can be routinely monitored from space, wind stress and sea surface temperature were most strongly correlated with chlorophyll across the BROKE-West survey area during the period of the survey. Each of these factors, as well as sea ice concentration, was found to be strongly correlated with chlorophyll at different locations. Three distinct regions were identified: The continental shelf and slope (max. depth=3000 m), where satellite data were most obstructed by ice and clouds, supported high concentrations of chlorophyll throughout the growth season (October to April), and although the most important factors determining chlorophyll were likely to be those not observable using remote sensing, close to 100% of variability in surface chlorophyll could be predicted by sea-surface temperature and sea ice concentration. Offshore to the west of 45°E, the eastern Weddell Gyre was found to retain sea-ice later into the growth season and support chlorophyll concentrations on the order of 0.1 mg m -3. Wind-driven advection of sea ice to the north and south of the Antarctic Divergence, located at 64°S, produced a strong positive correlation between chlorophyll concentrations along the landward and off-shore edges of the seasonal ice zone and the Southern Annular Mode. Offshore to the east of 45°E, chlorophyll concentrations encountered during the BROKE-West cruise were found to be unusually high. This was attributed to a southerly excursion of the Antarctic Circumpolar Current corresponding to negative Southern Annular Mode indices during the cruise. Significant, regionally varying correlations were found between the physical and biological parameters examined and climatological indices, including the Southern Annular Mode and the tropical El Nino-Southern Oscillation signal. © 2010 Elsevier Ltd.