The effects of continental margins and water mass circulation on the distribution of dissolved aluminum and manganese in Drake Passage

Abstract

A total of 232 samples were analyzed for concentrations of dissolved aluminum ([Al]) and manganese ([Mn]) in Drake Passage. Both [Al] and [Mn] were extremely low (∼0.3 and 0.1 nM, respectively) in the surface layer of the middle Drake Passage, most likely due to limited input and biological uptake/scavenging. Elevated [Al] (>14 nM) and [Mn] (>2 nM) over the South American continental shelf are related to land run‐off, whereas elevated concentrations (>1 nM and >2 nM, respectively) near the Antarctic Peninsula are most likely related to sediment re‐suspension. Re‐suspension of sedimentary particles and pore waters influences the distribution of [Al] and [Mn] over the continental slopes on both sides of Drake Passage. The influence of the continental margins and accumulated dust input potentially explains the higher [Al] observed eastward in the Atlantic section of the Southern Ocean. In the northern Drake Passage, elevated [Al] (∼0.8 nM) and [Mn] (∼0.3 nM) near the seafloor are most likely the result of bottom sediment re‐suspension by the relatively strong currents. In the deep southern Drake Passage sediment re‐suspension associated with the inflow of Weddell Sea Deep Water appears to cause elevated [Al] (>1 nM) and [Mn] (∼0.4 nM). In the deep northern Drake Passage, North Atlantic Deep Water brings in elevated [Al] and Southeast Pacific Deep Slope Water brings in the signature of Pacific hydrothermal vents. Elevated [Mn] andδ3He were correlated in this water layer and are most likely originating from the volcanically active ridges in the Pacific Ocean.