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Ocean Science An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/os-2017-100
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
15 Jan 2018
Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Ocean Science (OS).
Characteristics of Chromophoric and Fluorescent Dissolved Organic Matter in the Nordic Seas
Anna Makarewicz1, Piotr Kowalczuk1, Sławomir Sagan1, Mats A. Granskog2, Alexey K. Pavlov2, Agnieszka Zdun1, Karolina Borzycka1, and Monika Zabłocka1 1Institute of Oceanology, Polish Academy of Sciences, ul. Powstańców Warszawy 55, 81-712 Sopot, Poland
2Norwegian Polar Institute, Fram Centre, 9296 Tromsø, Norway
Abstract. Optical properties of Chromophoric (CDOM) and Fluorescent Dissolved Organic Matter (FDOM) were characterized in the Nordic Seas including the West Spitsbergen Shelf during June–July of 2013, 2014 and 2015. The CDOM absorption coefficient at 350 nm, aCDOM(350) showed significant interannual variation. In 2013, the highest average aCDOM(350) values (aCDOM = 0.30 ± 0.12 m−1) were observed due to the influence of cold and low–saline water from the Sørkapp Current in the southern part of West Spitsbergen Shelf. In 2014, aCDOM(350) values were significantly lower than in 2013 (av. aCDOM(350) = 0.14 ± 0.06 m−1), which was associated with the dominance of warm and saline Atlantic Water (AW) in the region, while in 2015 intermediate CDOM absorption (av. aCDOM(350) = 0.19 ± 0.05 m−1) was observed. In situ measurement of three FDOM components revealed that protein–like FDOM dominated and concentration of marine and terrestrial humic–like DOM were very low and its distribution were generally vertically homogenous in the upper ocean (0–100 m). Fluorescence of terrestrial and marine humic–like FDOM decreased in surface waters (0–15 m) near the sea–ice edge by dilution of oceanic waters by sea–ice melt water. The vertical distribution of protein–like FDOM was characterized by a prominent sub–surface maximum that matched the subsurface chlorophyll a maximum and was observed all across the study area. The highest protein–like FDOM fluorescence was observed in the Norwegian Sea in the core of warm AW. There was a significant relationship between the protein–like fluorescence and chlorophyll a fluorescence (R2 = 0.65, p < 0.0001, n = 24 490) and between the protein–like fluorescence intensity and chlorophyll a concentration in discrete water samples (R2 = 0.36, p < 0.0001, n = 299), which suggests that phytoplankton was the primary source of protein–like DOM in the Nordic Seas and West Spitsbergen Shelf waters. Observed variability range of selected spectral indices (spectral slope coefficient, S300–600, carbon specific CDOM absorption coefficient at 254 and 350 nm, SUVA254, aCDOM*(350)) and non–linear relationship between CDOM absorption and spectral slope coefficient indicate a dominant marine (autochthonous) source of CDOM and FDOM in the study area. Further, our data suggest that while aCDOM(350) cannot be used to predict dissolved organic carbon (DOC) concentrations in the study region, and the slope coefficient (S300–600) shows some promise to be used.
Citation: Makarewicz, A., Kowalczuk, P., Sagan, S., Granskog, M. A., Pavlov, A. K., Zdun, A., Borzycka, K., and Zabłocka, M.: Characteristics of Chromophoric and Fluorescent Dissolved Organic Matter in the Nordic Seas, Ocean Sci. Discuss., https://doi.org/10.5194/os-2017-100, in review, 2018.
Anna Makarewicz et al.
Anna Makarewicz et al.
Anna Makarewicz et al.

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