Mapping Areas of the Southern Ocean Where Productivity Likely Depends on Dust-Delivered Iron

Abstract

The existence of low-productivity areas in the Southern Ocean has been related to limited supply of bioavailable iron from terrestrial sources of dust. Dust-delivered iron can be crucial to ocean productivity, though alternative mechanisms have also been identified. To explore the geographic distribution of areas limited in the delivery of iron-rich atmospheric dust in the austral summer, we calculate forward trajectories from continental sources in the Southern Hemisphere between 2007 and 2015. A statistical comparison between trajectory patterns and maps of chlorophyll-a, an indicator of ocean productivity, shows a significant positive correlation in ocean areas between 45°S and 65°S, consistent with the dust deposition hypothesis. Likewise, considering the area south of 45°S, while excluding the coastal belt of Antarctica, a positive correlation is also found. These results suggest the existence of two potential sources of bioavailable iron to the Southern Ocean that determine its productivity patterns: aeolian transport from dust sources into the open Southern Ocean and coastal sediment and upwelling in the coastal Antarctic Ocean.