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An investigation of coloured dissolved organic matter (CDOM) and its relationships to physical and biogeochemical parameters in Antarctic sea ice and oceanic water have indicated that ice melt may both alter the spectral characteristics of CDOM in Antarctic surface waters and serve as a likely source of fresh autochthonous CDOM and labile DOC. Samples were collected from melted bulk sea ice, sea ice brines, surface gap layer waters, and seawater during three expeditions: one during the spring to summer and two during the winter to spring transition period. Variability in both physical (temperature and salinity) and biogeochemical parameters (dissolved and particulate organic carbon and nitrogen, as well as chlorophyll a) was observed during and between studies, but CDOMabsorption coefficients measured at 375 nm (a375) did not differ significantly. Distinct peaked absorption spectra were consistently observed for bulk ice, brine, and gap water, but were absent in the seawater samples. Correlation with the measured physical and biogeochemical parameters could not resolve the source of these peaks, but the shoulders and peaks observed between 260 and 280 nmand between 320 to 330 nmrespectively, particularly in the samples taken from high light-exposed gap layer environment, suggest a possible link to aromatic and mycosporine-like amino acids. Sea ice CDOM susceptibility to photo-bleaching was demonstrated in an in situ 120 hour exposure, during which we observed a loss in CDOM absorption of 53% at 280 nm, 58% at 330 nm, and 30% at 375 nm. No overall coincidental loss of DOC or DON was measured during the experimental period. A relationship between the spectral slope (S) and carbon-specific absorption (an 375) indicated that the characteristics of CDOM can be described by the mixing of two broad end-members; and aged material, present in brine and seawater samples characterised by high S values and low an 375; and a fresh material, due to elevated in situ production, present in the bulk ice samples characterised by low S and high an 375. The DOC data reported here have been used to estimate that approximately 8 Tg C yr1 (11% of annual sea ice algae primary production) may be exported to the surface ocean during seasonal sea ice melt in the form of DOC.

Item Type:	Refereed Article
Keywords:	Sea ice, Antarctic, Coloured dissolved organic matter (CDOM), Dissolved organic matter (DOM), Photochemistry, Biogeochemistry
Research Division:	Environmental Sciences
Research Group:	Ecological applications
Research Field:	Ecosystem function
Objective Division:	Environmental Policy, Climate Change and Natural Hazards
Objective Group:	Understanding climate change
Objective Field:	Effects of climate change on Antarctic and sub-Antarctic environments (excl. social impacts)
UTAS Author:	Meiners, KM (Dr Klaus Meiners)
UTAS Author:	Lannuzel, D (Associate Professor Delphine Lannuzel)
UTAS Author:	Van Der Merwe, P (Dr Pier van der Merwe)
ID Code:	72229
Year Published:	2011
Web of Science® Times Cited:	52
Deposited By:	IMAS Research and Education Centre
Deposited On:	2011-08-24
Last Modified:	2012-05-24
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