Particulate iron delivery to the water column of the Amundsen Sea, Antarctica

Hélène Planquette, Robert M. Sherrell, Sharon Stammerjohn, M. Paul Field

Research output: Contribution to journalArticle

Abstract

The Amundsen Sea, West Antarctica, is home to the most productive polynyas of the Southern Ocean, where summer primary production can reach 3gCm-2d-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 8-800m 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, 0.45-5μm and >5μm. Particulate Fe concentrations ranged from as low as 10pmolL-1 in open Antarctic Circumpolar Current (ACC) waters off the continental shelf to >100,000pmolL-1 near the Crosson Ice Shelf, and were dominated by particles>5μm 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 (0.45-5μm), 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.

Original languageEnglish (US)
Pages (from-to)15-30
Number of pages16
JournalMarine Chemistry
Volume153
DOIs
StatePublished - Jul 1 2013

Fingerprint

Iron
water column
continental shelf
iron
Water
ice shelf
resuspension
Ice
circumpolar current
biogeochemistry
shelf break
water
Sediments
sediment
bioavailability
water mass
trace metal
thinning
primary production
sea ice

All Science Journal Classification (ASJC) codes

  • Oceanography
  • Chemistry(all)
  • Environmental Chemistry
  • Water Science and Technology

Cite this

Planquette, Hélène ; Sherrell, Robert M. ; Stammerjohn, Sharon ; Field, M. Paul. / Particulate iron delivery to the water column of the Amundsen Sea, Antarctica. In: Marine Chemistry. 2013 ; Vol. 153. pp. 15-30.
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abstract = "The Amundsen Sea, West Antarctica, is home to the most productive polynyas of the Southern Ocean, where summer primary production can reach 3gCm-2d-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 8-800m 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, 0.45-5μm and >5μm. Particulate Fe concentrations ranged from as low as 10pmolL-1 in open Antarctic Circumpolar Current (ACC) waters off the continental shelf to >100,000pmolL-1 near the Crosson Ice Shelf, and were dominated by particles>5μm 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 (0.45-5μm), 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.",
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Particulate iron delivery to the water column of the Amundsen Sea, Antarctica. / Planquette, Hélène; Sherrell, Robert M.; Stammerjohn, Sharon; Field, M. Paul.

In: Marine Chemistry, Vol. 153, 01.07.2013, p. 15-30.

Research output: Contribution to journalArticle

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AU - Planquette, Hélène

AU - Sherrell, Robert M.

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N2 - The Amundsen Sea, West Antarctica, is home to the most productive polynyas of the Southern Ocean, where summer primary production can reach 3gCm-2d-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 8-800m 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, 0.45-5μm and >5μm. Particulate Fe concentrations ranged from as low as 10pmolL-1 in open Antarctic Circumpolar Current (ACC) waters off the continental shelf to >100,000pmolL-1 near the Crosson Ice Shelf, and were dominated by particles>5μm 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 (0.45-5μm), 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.

AB - The Amundsen Sea, West Antarctica, is home to the most productive polynyas of the Southern Ocean, where summer primary production can reach 3gCm-2d-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 8-800m 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, 0.45-5μm and >5μm. Particulate Fe concentrations ranged from as low as 10pmolL-1 in open Antarctic Circumpolar Current (ACC) waters off the continental shelf to >100,000pmolL-1 near the Crosson Ice Shelf, and were dominated by particles>5μm 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 (0.45-5μm), 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.

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