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Biogeosciences An interactive open-access journal of the European Geosciences Union
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© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 01 Mar 2019

Research article | 01 Mar 2019

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This discussion paper is a preprint. A revision of the manuscript is under review for the journal Biogeosciences (BG).

Dissolved Organic Matter at the Fluvial-Marine Transition in the Laptev Sea Using in situ Data and Ocean Color Remote Sensing

Bennet Juhls1, Pier Paul Overduin2, Jens Hölemann3, Martin Hieronymi4, Atsushi Matsuoka5, Birgit Heim2, and Jürgen Fischer1 Bennet Juhls et al.
  • 1Institute for Space Sciences, Department of Earth Sciences, Freie Universität Berlin, Berlin, Germany
  • 2Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany
  • 3Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
  • 4Institute of Coastal Research, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany
  • 5Takuvik Joint International Laboratory, Département de Biologie, Université Laval, Canada

Abstract. River water is the main source of dissolved organic carbon (DOC) in the Arctic Ocean. DOC plays an important role in the Arctic carbon cycle and its export from land to sea is expected to increase as ongoing climate change accelerates permafrost thaw. However, transport pathways and transformation of DOC in the land-to-ocean transition are mostly unknown. We collected DOC and aCDOM(λ) samples from 11 expeditions to river, coastal and offshore waters and present a new DOC-aCDOM(λ) model for the fluvial-marine transition zone in the Laptev Sea The aCDOM(λ) characteristics revealed that the DOM in samples of this dataset are primarily of terrigenous origin. Observed changes in aCDOM and its spectral slopes indicate that DOM is modified by microbial- and photo-degradation. Ocean Color Remote Sensing (OCRS) provides the absorption coefficient of colored dissolved organic matter (aCDOM(λ)sat) at λ = 440 or 443 nm, which can be used to estimate DOC concentration at high temporal and spatial resolution over large regions. We tested the statistical performance of five OCRS algorithms and evaluated the plausibility of the spatial distribution of derived aCDOM(λ)sat. The ONNS algorithm showed the best performance compared to in situ aCDOM(440) (r2 = 0.72). Additionally, we found ONNS-derived aCDOM(440), in contrast to other algorithms, to be partly independent of sediment concentration, making ONNS the most suitable aCDOM(λ)sat algorithm for the Laptev Sea region. The DOC-aCDOM(λ) model was applied to ONNS-derived aCDOM(440) and retrieved DOC concentration maps showed moderate agreement to in situ data (r2 = 0.53). The in situ and satellite-retrieved data were offset by up to several days, which may partly explain the weak correlation for this dynamic region. Satellite-derived surface water DOC concentration maps from MERIS satellite data demonstrate rapid removal of DOC within short time periods in coastal waters of the Laptev Sea, which is likely caused by physical mixing and different types of degradation processes. Using samples from all occurring water types leads to a more robust DOC-aCDOM(λ) model for the retrievals of DOC in Arctic shelf and river waters.

Bennet Juhls et al.
Interactive discussion
Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Bennet Juhls et al.
Data sets

Surface water Dissolved Organic Matter (DOC, CDOM) in the Laptev Sea and Lena River B. Juhls, J. A. Hölemann, B. Heim, P. P. Overduin, R. Gonçalves-Araujo, M. Hieronymi, and J. Fischer

Bennet Juhls et al.
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Short summary
In this article, we present the variability and characteristics of Dissolved Organic Matter at the fluvial-marine transition in the Laptev Sea from a unique dataset collected during 11 Arctic expeditions. We develop a new relationship between Dissolved Organic Carbon (DOC) and Colored Dissolved Organic Matter absorption, which is used to estimate surface water DOC concentration from space. We believe that our findings help current efforts to monitor ongoing changes in the Arctic carbon cycle.
In this article, we present the variability and characteristics of Dissolved Organic Matter at...