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Other research product . 2018

Effects of the 2014 major Baltic inflow on methane and nitrous oxide dynamics in the water column of the central Baltic Sea

Myllykangas, Jukka-Pekka; Jilbert, Tom; Jakobs, Gunnar; Rehder, Gregor; Werner, Jan; Hietanen, Susanna;
Open Access
English
Published: 27 Sep 2018
Abstract

In late 2014, a large, oxygen-rich salt water inflow entered the Baltic Sea and caused considerable changes in deep water oxygen concentrations. We studied the effects of the inflow on the concentration patterns of two greenhouse gases, methane and nitrous oxide, during the following year (2015) in the water column of the Gotland Basin. In the eastern basin, methane which had previously accumulated in the deep waters was largely removed during the year. Here, volume-weighted mean concentration below 70 m decreased from 108 nM in March to 16.3 nM over a period of 141 days (0.65 nM d−1), predominantly due to oxidation (up to 79 %) following turbulent mixing with the oxygen-rich inflow. In contrast nitrous oxide, which was previously absent from deep waters, accumulated in deep waters due to enhanced nitrification following the inflow. Volume-weighted mean concentration of nitrous oxide below 70 m increased from 11.8 nM in March to 24.4 nM in 141 days (0.09 nM d−1). A transient extreme accumulation of nitrous oxide (877 nM) was observed in the deep waters of the Eastern Gotland Basin towards the end of 2015, when deep waters turned anoxic again, sedimentary denitrification was induced and methane was reintroduced to the bottom waters. The Western Gotland Basin gas biogeochemistry was not affected by the inflow.

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Funded by
AKA| Nitrogen processes in the water column of the Baltic Sea
Project
  • Funder: Academy of Finland (AKA)
  • Project Code: 139267
,
AKA| Biogeochemical links between climate change and eutrophication in the Baltic Sea
Project
  • Funder: Academy of Finland (AKA)
  • Project Code: 267112
,
AKA| Biogeochemical links between climate change and eutrophication in the Baltic Sea
Project
  • Funder: Academy of Finland (AKA)
  • Project Code: 272964
,
EC| EUROFLEETS2
Project
EUROFLEETS2
New operational steps towards an alliance of European research fleets
  • Funder: European Commission (EC)
  • Project Code: 312762
  • Funding stream: FP7 | SP4 | INFRA
Related to Research communities
European Marine Science
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