The impact of sedimentary alkalinity release on the water column CO2 system in the North Sea

[摘要] It has been previously proposed that alkalinity release from sediments canplay an important role in the carbonate dynamics on continental shelves,lowering the pCO₂ of seawater and hence increasing the CO₂ uptakefrom the atmosphere. To test this hypothesis, sedimentary alkalinitygeneration was quantified within cohesive and permeable sediments across theNorth Sea during two cruises in September 2011 (basin-wide) and June 2012(Dutch coastal zone). Benthic fluxes of oxygen (O₂), alkalinity(A_T) and dissolved inorganic carbon (DIC) were determined usingshipboard closed sediment incubations. Our results show that sediments canform an important source of alkalinity for the overlying water, particularlyin the shallow southern North Sea, where high A_T and DIC fluxeswere recorded in near-shore sediments of the Belgian, Dutch and Germancoastal zone. In contrast, fluxes of A_T and DIC are substantiallylower in the deeper, seasonally stratified, northern part of the North Sea.Based on the data collected, we performed a model analysis to constrain themain pathways of alkalinity generation in the sediment, and to quantify howsedimentary alkalinity drives atmospheric CO₂ uptake in the southern NorthSea. Overall, our results show that sedimentary alkalinity generation shouldbe regarded as a key component in the CO₂ dynamics of shallow coastalsystems.

[学科分类] 地球化学与岩石