High temporal resolution observations of spring fast ice melt and seawater iron enrichment in East Antarctica

• Published in: Journal of Geophysical Research
• Main Authors: Van Der Merwe, P, Lannuzel, D, Bowie, AR, Meiners, K
• Format: Article in Journal/Newspaper
• Language: English
• Published: Amer Geophysical Union 2011
• Subjects: Environmental Sciences; Ecological Applications; Ecosystem Function; Antarctic; Austral; East Antarctica; Southern Ocean; Antarc*; Antarctica; Antarctica Journal; Sea ice
• Online Access: https://doi.org/10.1029/2010JG001628; http://ecite.utas.edu.au/72246

A time series experiment was conducted in late austral spring(NovemberDecember 2009) in coastal fast ice, East Antarctica (6613!07"S,11039!02"E). Iron (Fe) measurements were made in sea ice, snow, brines,and underlying seawater, together with meteorological, physical, and biogeochemicalmeasurements to investigate the processes controlling the release of Fe into theunderlying water column. Warming air temperatures were clearly associated withdecreasing brine volume fractions. Macronutrient profiles revealed very low(<1 mM) nitrate + nitrite concentrations in the interior of the sea ice, and the brinessuggested nitrate + nitrite drawdown exceeded Redfield ratios in comparison tophosphate and silicate. In the basal ice, nitrate + nitrite and silicate were drawn downthrough time but did not lead to a limiting condition. We found that dissolved Fe trackedthe brine volume fraction and was readily transferred from the surface/interior to theunderlying water column over time. In contrast, particulate Fe did not show this cleardecreasing trend and correlated with particulate organic carbon and chlorophyll adistributions. Over the 28 d of sampling, two distinct mean air temperature warming eventswere observed (−12.1 to −1.3C and −6.4 to 0.8C). This resulted in the release of419 mmol of TDFe per m2 of sea ice from our coastal fast ice station into the underlyingwater column during the study period. Assuming an increase of 1 nM Fe is sufficientfor Antarctic diatoms to bloom, our study site presented a fertilization potential for419 m3 of Fe limited surface Southern Ocean seawater with TDFe and 29 m3 with dFe,per m2 of fast ice.