Journal
MARINE CHEMISTRY
Volume 153, Issue -, Pages 15-30Publisher
ELSEVIER
DOI: 10.1016/j.marchem.2013.04.006
Keywords
Polynyas; Suspended particulate matter; Trace elements; Ice shelves; Resuspended sediments; Southern Ocean; Amundsen Sea
Categories
Funding
- NSF [ANT 0741403, ANT 0741510]
- Directorate For Geosciences
- Office of Polar Programs (OPP) [1440435] Funding Source: National Science Foundation
- Office of Polar Programs (OPP)
- Directorate For Geosciences [0838975] Funding Source: National Science Foundation
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The Amundsen Sea, West Antarctica, is home to the most productive polynyas of the Southern Ocean, where summer primary production can reach 3 g C m(-2) d(-1). The remoteness of this region has meant that systematic studies of biogeochemistry in the Amundsen Sea polynyas have been limited, despite their importance to overall Antarctic shelf productivity and proximity to the fastest thinning glaciers on the continent. Particulate iron inputs to the productive shelf waters of the Amundsen Sea may be important to the overall bioavailability of Fe in this region of natural Fe fertilization. Here we discuss findings from the US-Swedish 2007-08 expedition aboard the I/B Oden, during which 12 stations were sampled for particulate trace metal analyses at depths of 8-800 m in the eastern and central polynyas as well as in sea ice covered waters, both on the Amundsen continental shelf and in deep waters north of the shelf break. Suspended particulate samples were collected in two size fractions, 0.45-5 mu m and >5 mu m. Particulate Fe concentrations ranged from as low as 10 pmol L-1 in open Antarctic Circumpolar Current (ACC) waters off the continental shelf to >100,000 pmol L-1 near the Crosson Ice Shelf, and were dominated by particles > 5 mu m at all stations. The relative concentrations of total particulate Fe, Al, Mn and P show the near-ubiquitous influence of crustal particles in the water column at stations on the Amundsen continental shelf. However, many samples had Fe/Al and Mn/Al ratios substantially in excess of mean crustal ratios, especially in the small size fraction (0.45-5 mu m), suggesting that more labile Fe oxyhydroxides and authigenic MnO2 phases, resulting from sediment resuspension, are also present at relatively high concentrations. In contrast, Fe/P ratios indicate that Fe associated with biogenic particles rarely accounts for more than 20% of total particulate Fe, even in offshore stations. A detailed examination of particulate elemental composition and spatial distribution in the context of water mass temperature and salinity gradients suggests that particle delivery processes associated with melting ice shelves and sediment resuspension dominate the particulate Fe sources to the Amundsen Sea water column. (C) 2013 Elsevier B.V. All rights reserved.
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