Climatic Influences on Southern Hemisphere Oceanic Primary Production Derived From Satellite Remote Sensing Observations

Oceanic phytoplankton growth is essential to the sustainability of ocean biota (Field et al. 1998). Ocean’s primary productivity varies in response to environmental conditions, such as sunlight and nutrient availability. These factors restrain the reproduction and growth of drifting algae. In the southern hemisphere several climate signals exist which may modulate ocean primary productivity such as the El Niño Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD) in the tropical Indo-Pacific region (Saji et al. 1999; Wolter; Timlin 1998) ; and the Southern Annular Mode (SAM) in the polar and sub-polar regions (Mo 2000a). Ocean primary productivity is thought to response indirectly to these climate modes of variability, by the circulation changes that these induce (Behrenfeld et al. 2006). Changing circulation patterns may origin an anomalous upwelling (or downwelling), leaving anomalous nutrient signatures in the euphotic layer, where primary productivity will anomaly correspond (Lovenduski; Gruber 2005). Additionally, the southern hemisphere also includes the unique region of the Southern Ocean, which is a critical component of the global circulation and the biogeochemical cycles of nutrients and carbon (Arrigo et al. 2008). Phytoplankton growth patterns adapt to different regions depending on the intrinsic conditions of each region. As vast and rapidly changing as the ocean is, satellite imagery provides an ideal tool to observe and illustrate, at a high sampling rate, several oceanic characteristics, including its colour (McClain et al. 2004). Using the appropriate algorithm, one is able to retrieve not only chlorophyll concentrations, from satellite observations but also phytoplankton estimates (Morel; Berthon 1989). In this study we use Empirical Orthogonal Functions (EOF) to evaluate satellite derived chlorophyll concentrations. The use of EOF is an ideal tool to observe cyclical patterns within continuous observations (Bjornsson; Venegas 1997). This paper explores the relationship between large-scale climate modes of variability (ENSO, IOD and SAM) and phytoplankton distribution patterns across the southern hemisphere oceans.