Observations of chromophoric dissolved and detrital organic matter distribution using remote sensing in the Southern Ocean: Validation, dynamics and regulation

Abstract

Chromophoric dissolved and detrital organic matter (CDM), the optically active fraction of organic matter, affects significantly the underwater light environment and interferes with ocean color algorithms. Here, we studied the distribution and dynamics of CDM in waters around the Antarctic Peninsula, Southern Ocean, using remotely sensed data in austral summers from 1997 to 2005. First, we validated the global semi-analytic algorithm Garver–Siegel–Maritorena (GSM) by comparing simultaneous field and satellite measurements of CDM. These comparisons confirmed the validity of CDM satellite measurements obtained by the GSM algorithm (r 2 = 0.74, slope value = 1.01 ± 0.16, n = 15).We found a higher (20%) contribution of detrital particles to the CDM signal compared to other studies in lower latitudes (average 12%). Patches of higher CDM were observed in coastal areas and zones with recent ice melting. The seasonal variability of CDM, with maximum values at the end of austral summer, appeared to be ultimately controlled by the dynamics of ice, both directly and indirectly through the growth of phytoplankton and other organisms which are potential sources of CDM. At an interannual timescale, CDM dynamics may be driven by climatic forcing such as the Antarctic Oscillation.