image: This image shows the emission and transport of dust and other important tropospheric aerosols to the Southern Ocean on 30 Dec. of 2006. The image is from a global simulation with GEOS-5 Earth system model, which includes aerosol processes from the GOCART model. Dust is represented with orange to red colors, sea salt with blue, organic and black carbon with green to yellow, and sulfates with ash brown to white. In the image, a plume of dust has been emitted from southern South America and is being transported eastward over the Subantarctic Atlantic Ocean. Dust plays an important role in ocean biogeochemical cycles by supplying iron and other metals to remote areas of the ocean. The Southern Ocean is the largest region of the ocean where the building-block nutrients nitrogen and phosphorus are not completely utilized for algal growth due to the scarcity of iron. The Subantarctic Zone, the more northern part of the Southern Ocean, sits under the path of the winds that blow off South America, South Africa, and Australia and is thus the region most likely to be fertilized by iron-rich dust. Martinez-Garcia et al. show that, during the last ice age, an increase in the supply of dust to the Subantarctic region of the Southern Ocean fertilized the ocean, stimulating marine productivity and causing nitrogen to be drawn down to low levels. The associated increase in the efficiency of carbon sequestration into the deep ocean can explain part of the atmospheric CO2 decrease observed during the last ice age. This image relates to a paper that appeared in the 21 March, 2014, issue of Science, published by AAAS. The paper, by Alfredo Martínez-García at ETH Zürich in Zurich, Switzerland, and colleagues was titled, "Iron Fertilization of the Subantarctic Ocean During the Last Ice Age." view more
Credit: [Image courtesy of William M. Putman and Arlindo M. da Silva (NASA/Goddard Space Flight Center)]