资源环境科技发展态势分析平台

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 degrees S and 65 degrees S, consistent with the dust deposition hypothesis. Likewise, considering the area south of 45 degrees 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.

Plain Language Summary Iron is a limiting micronutrient in high-nutrient, low-chlorophyll waters of the Southern Ocean, and atmospheric dust from continental sources is considered to be one of the sources of bioavailable iron. Given the relatively few number of dust sources in the Southern Hemisphere, it is important to quantify the distribution of dust in the remote waters of the Southern Ocean and thus investigate ocean regions that likely depend on atmospheric dust for primary productivity. Using modeled pathways of air parcel trajectories starting from each dust source area in South America, Southern Africa, and Australia and average chlorophyll-a concentrations in the Southern Ocean, we found a positive relationship between ocean productivity and trajectory densities within areas that are further away from the coastal belt of Antarctica. Our results suggest that ocean productivity along the Antarctic coast is dependent on other sources of iron such as sedimentary inputs and upwelling, and dust emitted from major continental sources in the Southern Hemisphere is perhaps not contributing to the observed biological activity near the Antarctic coast.