Simultaneous remote sensing of chlorophyll, sea ice and sea surface temperature in the Antarctic waters with special reference to the primary production from ice algae

Abstract

The primary production of the Antarctic Ocean south of 60°S was studied by using monthly chlorophyll- a concentration (Chl) and sea surface temperature (SST) from November 1996 to April 1997, as observed by the Ocean Color and Temperature Sensor (OCTS) aboard the Advanced Earth Observing Satellite (ADEOS). The area was divided into six sectors: (A) West and (a) East Pacific, (B) West and (b) East Atlantic, and (C) West and (c) East Indian Ocean. Sectors (A), (B), and (C) showed high Chl, and (a), (b), and (c) showed low Chl. The high Chl sectors were characterized by the wide ice covered area in spring and summer. The average Chl was 0.35 mg/m 3. A high Chl of 0.6–2.1 mg/m 3 was found only at the ice melting area (SST below 0°) and probably originated from the liberation of the seasonal primary production by ice algae. The result shows a strong contribution of sea ice and ice algae to primary production and to the regionally heterogeneous Chl distribution by the drifting of Chl-containing ice to the melting spots. We propose a hypothesis of iron supply via snow covered sea ice as follows: iron is (1) collected from the atmosphere, (2) made soluble, (3) supplied vertically to the ice algae below, (4) taken up by diatom cells, and (5) transported to the ice melting areas.