Characterizing spatial distribution of chlorophyll a in the Southern Ocean on a circumpolar cruise in summer

The spatial variation of chlorophyll a in the Southern Ocean (SO) was of great significance. Sea surface chlorophyll a concentrations was measured by Ferry Box monitoring system on the Chinese polar research vessel Xue Long, which circumnavigated the Antarctic continent in a clockwise direction during the austral summer 2013-2014 (November 2013-April 2014). The concentrations of chlorophyll a indicated a relatively uniform distribution of 0.049-11.647 mg m^-3 (mean 0. 869 mg m^-3, n = 152,751). The highest chlorophyll a concentrations (mean 1.847 mg m^-3) was found in the Ross sea (RS). In addition, six high-chlorophyll a hot spots were recognized. Analysis revealed that phytoplankton bloom could be controlled by multiple factors in different regions, and the chlorophyll a bloom is attributed to the combined effect of surface and subsurface processes such as, continental shelf, sea ice melting, Circumpolar Deep Water (CDW) upwelling, suitabletemperature, and nutrient injection from subsurface to the surface. The topographic effects, sea ice melting and CDW upwelling may play a major role in controlling primary productivity in the SO. Among of all, CDW upwelling may be the most important role improving primary productivity. This study presented the phytoplankton distribution patterns and the relation with potential growth-controlling factors in the SO, which will provide more insight in the mechanisms that control global warming to reduce global CO₂ the atmosphere into the ocean interior.