Preprints
https://doi.org/10.5194/os-2021-90
https://doi.org/10.5194/os-2021-90

  06 Oct 2021

06 Oct 2021

Review status: this preprint is currently under review for the journal OS.

Inherent optical properties and optical characteristics of dissolved organic and particulate matter in an Arctic fjord (Storfjorden, Svalbard) in early summer

Tristan Petit1,2, Børge Hamre2, Håkon Sandven2, Rüdiger Röttgers3, Piotr Kowalczuk4, Monika Zablocka4, and Mats Granskog1 Tristan Petit et al.
  • 1Norwegian Polar Institute, Fram Centre, Tromsø, Norway
  • 2University of Bergen, Institute of Physics and Technology, Bergen, Norway
  • 3Helmholtz-Zentrum Hereon, Institute of Coastal Ocean Dynamics, Geesthacht, Germany
  • 4Institute of Oceanology, Polish Academy of Sciences, Sopot, Poland

Abstract. There have been considerable efforts to understand the hydrography of the Storfjorden fjord (Svalbard). A recurring winter polynya with large sea ice production makes it an important region of dense water formation at the scale of the Arctic Ocean. In addition, this fjord is seasonally influenced by freshwater inputs from sea-ice melt and the surrounding islands of the Svalbard archipelago which impacts the hydrography. However, the understanding of factors controlling the optical properties of the waters in Storfjorden are lacking and are crucial for development of more accurate regional bio-optical models. Here, we present results from the first detailed optical field survey of Storfjorden conducted in early summer of 2020. In addition to the expected seasonal contribution from phytoplankton, we find that in early summer waters in Storfjorden are optically complex with a significant contribution from coloured dissolved organic matter (33–64 % of the non-water absorption at 443 nm) despite relatively low CDOM concentrations, and in the nearshore or near seabed from non-algal particles (up to 61 % of the non-water absorption at 550 nm). In surface waters, the spatial variability of light attenuation was mainly controlled by inorganic suspended matter originating from river runoff. A distinct subsurface maximum of light attenuation was largely driven by a subsurface phytoplankton bloom, controlled by stratification resulting from sea-ice melt. Lastly, the cold dense bottom waters of Storfjorden, from winter sea ice production, which periodically overflows into the Fram Strait, was found to contain elevated levels of both non-algal particles and dissolved organic matter, which is likely caused by the dense flows of the nepheloid layer interacting with the sea bed.

Tristan Petit et al.

Status: open (until 01 Dec 2021)

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Tristan Petit et al.

Tristan Petit et al.

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Short summary
Storfjorden (Svalbard) is an important arctic ice factory. Information on the factors controlling light propagation in this fjord becomes crucial in times of rapid ice decline. We measured spatial and vertical variations of the optical properties in the Storfjorden. We find significant contribution from dissolved matter to the light absorption as well as subsurface absorption maximum linked to algae production. Dense bottom water has elevated levels of dissolved and particulate matters.