Nd isotopic constraints on the origin of suspended particles in the Atlantic sector of the Southern Ocean

In the nutrient-rich Southern Ocean, Fe is a vital constituent controlling the growth of phytoplankton. Despite much effort, the origin and transport of Fe to the oceans are not well understood. In this study we address the issue with geochemical data and Nd isotopic compositions of suspended particle samples collected from 1997 to 1999 in the South Atlantic Sector of the Southern Ocean. Al, Th, and rare earth element (REE) concentrations as well as 143 Nd/144 Nd isotopic ratios in acetic acid-leached particle samples representing the lithogenic fraction delineate three major sources: (1) Patagonia and the Antarctic Peninsula provide material with epsilon(Nd) > -4 that is transported toward the east with the polar and subpolar front jets, (2) the south African shelf, although its influence is limited by the circumpolar circulation and wind direction, can account for material with epsilon(Nd) of -12 to -14 adjacent to South Africa, and (3) East Antarctica provides material with epsilon(Nd) of -10 to -15 to the eastern Weddell Sea and adjacent Antarctic Circumpolar Current. For this region we interpret the Nd isotopic evidence in combination with oceanographic/atmospheric constraints as evidence for supply of significant amounts of terrigenous detritus by icebergs.