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

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 (similar to 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] (similar to 0.8 nM) and [Mn] (similar to 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] (similar to 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] and delta He-3 were correlated in this water layer and are most likely originating from the volcanically active ridges in the Pacific Ocean.