Trace metal and nutrient dynamics across broad biogeochemical gradients in the Indian and Pacific sectors of the Southern Ocean

• Published in: Marine Chemistry
• Main Authors: Janssen, David J., Sieber, M., Ellwood, Michael, Conway, Tim M., Barrett, Pamela, Chen, Xiaoyu, de Souza, Gregory F., Hassler, Christel S., Jaccard, Samuel
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier
• Subjects: Trace Metal; Southern Ocean; GEOTRACES; Iron; Antarctic Circumnavigation Expedition; Antarctic; The Antarctic; Austral; Balleny Islands; Pacific; Indian; Mertz Glacier; Antarc*
• Online Access: http://hdl.handle.net/1885/218996; https://doi.org/10.1016/j.marchem.2020.103773; https://openresearch-repository.anu.edu.au/bitstream/1885/218996/3/01_Janssen_Trace_metal_and_nutrient_2020.pdf.jpg

The Southern Ocean is the largest high-nutrient low-chlorophyll environment in the global ocean, and represents an important source of intermediate and deep waters to lower latitudes. Constraining Southern Ocean trace metal biogeochemical cycling is therefore important not just for understanding biological productivity and carbon cycling regionally, but also for understanding trace metal distributions throughout the lower latitude oceans. We present dissolved Fe, Ni, Cu, Zn, Cd, Pb and macronutrient concentrations in the Indian and Pacific sectors of the Southern Ocean from the Antarctic Circumnavigation Expedition (austral summer 2016-17), which included the first opportunities to study trace metal cycling at the Mertz Glacier Polynya and the Balleny Islands, as well as two meridional cross-frontal transects. Dissolved Ni, Cu, Zn, Cd and macronutrient concentrations show similar or greater variability latitudinally within surface waters than vertically through the water column, reflecting the combined influence of circulation and biological drawdown in shaping the distributions of nutrient-type elements in the Southern Ocean. Slopes of Cu-Si(OH)4 and Cd-PO4 increase from the Polar Frontal Zone to south of the Southern ACC Boundary (Cu-Si(OH)4) and from the Subantarctic Zone to the Antarctic Zone (Cd-PO4). Latitudinal differences are also observed for Ni-Si(OH)4 and Zn-PO4, with distinct Subantarctic Zone trends relative to those south of the Polar Front. Similarities between our Zn-Si(OH)4 and Cd-PO4 correlations and global compilations reflect the importance of exported Southern Ocean waters in setting these metal-macronutrient couples globally. Distinct Ni-macronutrient correlations are observed in this dataset relative to the global ocean, which supports a distinct cycling of Ni in the Southern Ocean compared to other basins. Concentrations of Pb are among the lowest observed in the global ocean; however, a local maximum is seen along the density level corresponding with Antarctic Intermediate Water. ...