Abstract <p>Data from 119 Bio-Argo floats for 2010–2021 are used to study the spatial and temporal variability of the vertical distribution of the chlorophyll <i>a</i> (<i>Chl</i>) concentration in various areas of the Southern Ocean. The results show that the variability of <i>Chl</i> is significantly influenced by two physical mechanisms of macronutrient supply, separated in time and space. In the Antarctic summer (January–March), the maximum increase in <i>Chl</i> is observed in three areas of intense offshore fluxes of melting ice from Antarctica (Weddell Sea, Amundsen Sea and the eastern part of the Indian Ocean sector). The greatest increase is recorded in the upper 0–50 layer m, with a maximum in the western part of the Atlantic sector of the Southern Ocean. The minimum values during this period in the upper layer are observed in the central part of the Pacific and Indian oceans. In the Antarctic spring (October–December), the maximum integrated <i>Chl</i> values are concentrated in the cyclonic shear zone on the southern periphery of the Antarctic Circumpolar Current. The greatest increase is recorded in the 50–100 m layer, corresponding to the lower part of the subsurface <i>Chl</i> peak, which is presumably associated with the vertical rise of nutrients in this zone. It is also shown that in areas of the highest <i>Chl</i> concentration, its subsurface maximum is situated closer to the surface, and in the deep layers <i>Chl</i> sharply decreases. In the central part of the oceans with relatively low <i>Chl</i> values in the upper layer, the subsurface peak is deeper (50–70 m) and the <i>Chl</i> values in the deep layers are higher. Here the seasonal cycle is less pronounced and <i>Chl</i> is more evenly distributed in depth.</p>