Multiple sources of soluble atmospheric iron to Antarctic waters

The Ross Sea, Antarctica, is a highly productive region of the Southern Ocean. Significant new sources of iron (Fe) are required to sustain phytoplankton blooms in the austral summer. Atmospheric deposition is one potential source. The fractional solubility of Fe is an important variable determining...

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Bibliographic Details
Published in:Global Biogeochemical Cycles
Main Authors: Winton, VHL, Edwards, R, Delmonte, B, Ellis, A, Andersson, PS, Bowie, A, Bertler, NAN, Neff, P, Tuohy, A
Format: Article in Journal/Newspaper
Language:English
Published: Amer Geophysical Union 2016
Subjects:
Earth Sciences
Oceanography
Chemical Oceanography
Antarctic
Austral
Roosevelt Island
Ross Sea
Southern Ocean
Antarc*
Antarctica
Online Access:https://doi.org/10.1002/2015GB005265
http://ecite.utas.edu.au/108914
Description
Summary:The Ross Sea, Antarctica, is a highly productive region of the Southern Ocean. Significant new sources of iron (Fe) are required to sustain phytoplankton blooms in the austral summer. Atmospheric deposition is one potential source. The fractional solubility of Fe is an important variable determining Fe availability for biological uptake. To constrain aerosol Fe inputs to the Ross Sea region, fractional solubility of Fe was analyzed in a snow pit from Roosevelt Island, eastern Ross Sea. In addition, aluminum, dust, and refractory black carbon (rBC) concentrations were analyzed, to determine the contribution of mineral dust and combustion sources to the supply of aerosol Fe. We estimate exceptionally high dissolved Fe (dFe) flux of 1.2 10 −6 g m −2 y −1 and total dissolvable Fe flux of 140 10 −6 g m −2 y −1 for 2011/2012. Deposition of dust, Fe, Al, and rBC occurs primarily during spring-summer. The observed background fractional Fe solubility of ~0.7% is consistent with a mineral dust source. Radiogenic isotopic ratios and particle size distribution of dust indicates that the site is influenced by local and remote sources. In 2011/2012 summer, relatively high dFe concentrations paralleled both mineral dust and rBC deposition. Around half of the annual aerosol Fe deposition occurred in the austral summer phytoplankton growth season; however, the fractional Fe solubility was low. Our results suggest that the seasonality of dFe deposition can vary and should be considered on longer glacial-interglacial timescales.

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