Colloquium: Heidi Dierssen
ABSTRACT: The Southern Ocean ranges from highly productive coastal regions of the Antarctic Peninsula to the low productivity regions of the South Indian Ocean and many different sources of particles exist within this gradient that contribute to particulate backscattering. Assemblages of different phytoplankton including diatoms, coccolithophores, and Phaeocystis dominate different zones of the region, as well as inorganic particle sources such as detached coccoliths, bubbles injected from breaking waves, and glacial flour from melting of land-based glaciers. This diversity creates unique influences on ocean color remote sensing that measure the magnitude of reflected light across visible wavelengths. For example, remotely derived estimates of light backscattering provide a means to estimate calcite concentrations, but coccolithophores are not found in the coldest waters near the Antarctic continent where high backscattering is attributed to glacial flour and near-surface colonial forms of Phaeocystis. Along the Polar Front prone to high winds, different sizes of bubbles contribute as much as 25% of the total particulate backscattering. Moreover, recent research has shown that proteins represent over 50% of the biomass of phytoplankton near the Antarctic Peninsula which can influence biogeochemical relationships between particulate backscattering and carbon. Here, I will give a brief introduction to ocean optics and explore how particle assemblages in the near surface Southern Ocean can be monitored with an aim towards understanding the biogeochemistry in this expansive and sensitive region of the world ocean.