UV/PAR radiations and DOM properties in surface coastal waters of the Canadian shelf of the Beaufort Sea during summer 2009

Abstract : Surface waters from the Beaufort Sea in the Arctic Ocean were evaluated for dissolved organic carbon (DOC), and optical characteristics including UV and PAR diffuse attenuation (Kd), and chromophoric and fluorescent dissolved organic matter (CDOM & FDOM) as part of the MALINA field campaign (30 July to 27 August). Spectral absorption coefficients (aCDOM(350 nm) (m-1)) were significantly correlated to both diffuse attenuation coefficients (Kd) in the UV-A and UV-B and to DOC concentrations. This indicates CDOM as the dominant attenuator of both UV-PAR solar radiation and suggests its use as an optical proxy for DOC concentrations in this region. While the Mackenzie input is the main driver of CDOM dynamics in low salinity waters, locally, primary production can create significant increases in CDOM. Extrapolating CDOM to DOC relationships, we estimate that ~16% of the DOC in the Mackenzie River does not absorb radiation at 350nm. The discharge of DOC and it chromophoric subset (CDOM) by the Mackenzie River during the MALINA cruise are estimated as ~ 0.22 TgC and 0.18 TgC, respectively. Three dissolved fluorescent components (C1-C3) were identified by fluorescence Excitation/Emission Matrix Spectroscopy (EEMS) and PARAFAC analysis. Our results showed an aquatic DOM component (C1), probably produced in numerous lakes of the watershed, that co-dominated with a terrestrial humic-like component (C2) in the Mackenzie Delta Sector. This aquatic DOM could partially explain the high CDOM spectral slopes observed in the Beaufort Sea.
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Submitted on : Thursday, April 4, 2013 - 11:11:31 PM
Last modification on : Saturday, May 25, 2019 - 1:42:37 AM

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J. Para, Bruno Charriere, Atsushi Matsuoka, W. Miller, Jean-Francois Rontani, et al.. UV/PAR radiations and DOM properties in surface coastal waters of the Canadian shelf of the Beaufort Sea during summer 2009. Biogeosciences, European Geosciences Union, 2013, 10, pp.2761-2774. ⟨10.5194/bg-10-2761-2013⟩. ⟨hal-00808123⟩

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