Interannual variability of diatom phenology in the Southern Ocean
Mariana Soppa1, Christoph D Voelker2 and Astrid Bracher1,3, (1)Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Bremerhaven, Bremerhaven, Germany, (2)Alfred Wegener Institute, Helmholtz-Center for Polar and Marine Research Bremerhaven, Bremerhaven, Germany, (3)University of Bremen, Institute of Environmental Physics, Bremen, Germany
Abstract:
Diatoms are the major primary producers and key players in the carbon and silicon pump in the Southern Ocean. Here we investigate the phenology of diatom blooms in the Southern Ocean over 15-yr using a regional model to retrieve diatoms abundance from satellite remote sensing observations. Different characteristics of the phenology (e.g. start, duration, biomass) are investigated, as well as the interannual variability and trends. In several areas, the interannual variability of the anomalies of the phenological indices is found to be correlated with the large scale climate oscillations El Niño Southern Oscillation (ENSO) and Southern Annular Mode (SAM). The composite maps of the anomalies revealed distinct spatial patterns and opposite events of ENSO and SAM have similar effects in the diatom phenology. For example, in the Ross Sea region, later start of the bloom and lower biomass were observed associated with El Niño and negative SAM events; likely influenced by an increase in sea ice concentration during these events. These results emphasize the influence of climate oscillations over the SO and in the diatom phenology, which may be enhanced in amplified years (e.g. El Niño and negative SAM events).
