Inhaltszusammenfassung

In recent decades, the central North Sea has been experiencing a general trend of decreasing dissolved oxygen (O-2) levels during summer. To understand potential causes driving lower O-2, we investigated a 3-day period of summertime turbulence and O-2 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 O-2 and organic carbon turnover within the BBL. Combining our flux observa...In recent decades, the central North Sea has been experiencing a general trend of decreasing dissolved oxygen (O-2) levels during summer. To understand potential causes driving lower O-2, we investigated a 3-day period of summertime turbulence and O-2 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 O-2 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 O-2 levels. We report substantial turbulent O-2 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 O-2 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 O-2 concentrations. This process may become suppressed with warming climate and stronger stratification, conditions which could promote migrating algal species that potentially shift the O-2 production zone higher up within the thermocline. » weiterlesen» einklappen

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