Satellite ocean color studies of Antarctic ice edges in summer and autumn

Large areas of elevated phytoplankton pigment concentrations were observed using CZCS satellite data in the Weddell Sea marginal ice zone and adjacent regions during the austral summer‐autumn transition. The study was made in conjunction with in situ observations of pigment levels and ice data derived from satellite passive microwave observations. The area of satellite investigation includes the eastern and western parts of the Weddell Sea and the western part of the Antarctic Peninsula. Phytoplankton blooms, about 200 km wide and extending several hundred kilometers along the ice edge, were observed. Higher pigment values in the south than in the north indicate that irradiance is not the only factor controlling spatial distributions of phytoplankton pigment concentrations at this time. A time series in Marguerite Bay also shows the persistence of a bloom for at least 12 days and significant effects on spatial distribution of the phytoplankton due to ocean and sea ice movement. An unusual pattern of sea ice formation in the Weddell Sea was also observed in a series of CZCS images near the Greenwich meridian. Turbulent oceanic and atmospheric forcings are suggested during the early stages of development of sea ice in the region and may account for the low pigment concentrations observed adjacent to the area. This study shows that ice edge phytoplankton blooms are not simply a spring‐summer feature but extend into the austral autumn and that they may contribute significantly to regional productivity.