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Seasonal variability of stable carbon isotopes (δ13CDIC) in the Skagerrak and the Baltic Sea : Distinguishing between mixing and biological productivity

Filipsson, Helena L. LU ; McCorkle, Daniel C.; Mackensen, Andreas; Bernhard, Joan M.; Andersson, Lars S.; Naustvoll, Lars Johan; Caballero-Alfonso, Angela M. LU ; Nordberg, Kjell and Danielssen, Didrik S. (2016) In Palaeogeography, Palaeoclimatology, Palaeoecology
Abstract

We documented the annual cycle of the carbon isotopic composition of dissolved inorganic carbon (δ13CDIC) in the water columns of the Skagerrak and Baltic Sea to obtain an increased understanding of the processes involved controlling the carbon isotopic distribution in shelf seas. The lowest δ13CDIC values (-4.9‰) were found in the low-oxygen, brackish Baltic bottom water whereas the highest values (+1.8‰) were observed in the surface water of the Skagerrak during late summer. Photosynthesis drove the high δ13CDIC values (between 1.0 and 1.8‰) noted in the surface waters of both the Skagerrak and the Baltic. The δ13CDIC values below the halocline in... (More)

We documented the annual cycle of the carbon isotopic composition of dissolved inorganic carbon (δ13CDIC) in the water columns of the Skagerrak and Baltic Sea to obtain an increased understanding of the processes involved controlling the carbon isotopic distribution in shelf seas. The lowest δ13CDIC values (-4.9‰) were found in the low-oxygen, brackish Baltic bottom water whereas the highest values (+1.8‰) were observed in the surface water of the Skagerrak during late summer. Photosynthesis drove the high δ13CDIC values (between 1.0 and 1.8‰) noted in the surface waters of both the Skagerrak and the Baltic. The δ13CDIC values below the halocline in the Baltic reflect mixing of brackish water and the more saline water from the Skagerrak, and foremost organic matter remineralization processes that release significant amounts of low-δ13C CO2. Similarly, in the stagnant fjord basins, little deep water exchange and the degradation of terrestrial and marine organic matter set the δ13C composition. Deep-water renewal in the fjord basins resulted in rapid increases of the δ13CDIC on the order of 1‰, whereas remineralization processes caused a decrease in δ13CDIC of 0.1-0.3‰ per month depending on location. The combined effects of water mixing and remineralization processes (estimated using apparent oxygen utilization (AOU) values) yielded the expression: δ13CDIC =0.032*S-0.01*AOU-0.12 for the Baltic - Skagerrak region at water depths below the halocline.

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author
organization
publishing date
type
Contribution to journal
publication status
epub
subject
keywords
Anoxia, AOU, DIC, Estuary, Hypoxia, Time-series
in
Palaeogeography, Palaeoclimatology, Palaeoecology
publisher
Elsevier
external identifiers
  • scopus:85007293894
ISSN
0031-0182
DOI
10.1016/j.palaeo.2016.11.031
language
English
LU publication?
yes
id
9ec23450-c14f-4584-8c85-2f53b59edfd8
date added to LUP
2017-04-19 14:04:33
date last changed
2017-04-19 14:04:33
@article{9ec23450-c14f-4584-8c85-2f53b59edfd8,
  abstract     = {<p>We documented the annual cycle of the carbon isotopic composition of dissolved inorganic carbon (δ<sup>13</sup>C<sub>DIC</sub>) in the water columns of the Skagerrak and Baltic Sea to obtain an increased understanding of the processes involved controlling the carbon isotopic distribution in shelf seas. The lowest δ<sup>13</sup>C<sub>DIC</sub> values (-4.9‰) were found in the low-oxygen, brackish Baltic bottom water whereas the highest values (+1.8‰) were observed in the surface water of the Skagerrak during late summer. Photosynthesis drove the high δ<sup>13</sup>C<sub>DIC</sub> values (between 1.0 and 1.8‰) noted in the surface waters of both the Skagerrak and the Baltic. The δ<sup>13</sup>C<sub>DIC</sub> values below the halocline in the Baltic reflect mixing of brackish water and the more saline water from the Skagerrak, and foremost organic matter remineralization processes that release significant amounts of low-δ<sup>13</sup>C CO<sub>2</sub>. Similarly, in the stagnant fjord basins, little deep water exchange and the degradation of terrestrial and marine organic matter set the δ<sup>13</sup>C composition. Deep-water renewal in the fjord basins resulted in rapid increases of the δ<sup>13</sup>C<sub>DIC</sub> on the order of 1‰, whereas remineralization processes caused a decrease in δ<sup>13</sup>C<sub>DIC</sub> of 0.1-0.3‰ per month depending on location. The combined effects of water mixing and remineralization processes (estimated using apparent oxygen utilization (AOU) values) yielded the expression: δ<sup>13</sup>C<sub>DIC</sub> =0.032*S-0.01*AOU-0.12 for the Baltic - Skagerrak region at water depths below the halocline.</p>},
  author       = {Filipsson, Helena L. and McCorkle, Daniel C. and Mackensen, Andreas and Bernhard, Joan M. and Andersson, Lars S. and Naustvoll, Lars Johan and Caballero-Alfonso, Angela M. and Nordberg, Kjell and Danielssen, Didrik S.},
  issn         = {0031-0182},
  keyword      = {Anoxia,AOU,DIC,Estuary,Hypoxia,Time-series},
  language     = {eng},
  month        = {11},
  publisher    = {Elsevier},
  series       = {Palaeogeography, Palaeoclimatology, Palaeoecology},
  title        = {Seasonal variability of stable carbon isotopes (δ<sup>13</sup>C<sub>DIC</sub>) in the Skagerrak and the Baltic Sea : Distinguishing between mixing and biological productivity},
  url          = {http://dx.doi.org/10.1016/j.palaeo.2016.11.031},
  year         = {2016},
}