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Thermocline mixing and vertical oxygen fluxes in the stratified central North Sea

Rovelli, Lorenzo
Dengler, Marcus
Schmidt, Mark
Sommer, Stefan
Linke, Peter
Published in Biogeosciences. 2016, vol. 13, no. 5, p. 1609-1620
Abstract In recent decades, the central North Sea has been experiencing a general trend of decreasing dissolved oxygen (O2) levels during summer. To understand potential causes driving lower O2, we investigated a 3-day period of summertime turbulence and O2 dynamics in the thermocline and bottom boundary layer (BBL). The study focuses on coupling biogeochemical with physical transport processes to identify key drivers of the O2 and organic carbon turnover within the BBL. Combining our flux observations with an analytical process-oriented approach, we resolve drivers that ultimately contribute to determining the BBL O2 levels. We report substantial turbulent O2 fluxes from the thermocline into the otherwise isolated bottom water attributed to the presence of a baroclinic near-inertial wave. This contribution to the local bottom water O2 and carbon budgets has been largely overlooked and is shown to play a role in promoting high carbon turnover in the bottom water while simultaneously maintaining high O2 concentrations. This process may become suppressed with warming climate and stronger stratification, conditions which could promote migrating algal species that potentially shift the O2 production zone higher up within the thermocline.
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Research groups Aquatic Physics
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ROVELLI, Lorenzo et al. Thermocline mixing and vertical oxygen fluxes in the stratified central North Sea. In: Biogeosciences, 2016, vol. 13, n° 5, p. 1609-1620. doi: 10.5194/bg-13-1609-2016 https://archive-ouverte.unige.ch/unige:85606

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Deposited on : 2016-08-02

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