Geologic history of seawater: A MAGic approach to carbon chemistry and ocean ventilation

摘要: Abstract We explore the relationship between atmospheric O 2 and CO evolution seawater chemistry, with particular focus on –carbonic acid system ocean ventilation, over Phanerozoic Eon using a coupled biogeochemical Earth model ( MAGic ). This describes cycles involving major components of (Ca, Mg, Na, K, Cl, SO 4 , HCO 3 ), as well (O Fe, P, organic C, reduced S) central to long-term ecosystem productivity. The calculations show that first-order input fluxes from weathering continental rocks Ca, dissolved inorganic carbon (DIC) varied in cyclical manner Phanerozoic. cyclicity is mainly result impact changing levels, hence temperature runoff, these fluxes, reflecting nature hothouse (greenhouse, high warm) versus icehouse (low cool, glaciation) conditions during Uptake DIC by seafloor basalt–seawater reactions also corresponding fashion fluxes. other constituents removed oceanic sinks were calculated inputs outputs constituents, changes chemistry through time could be obtained. Seawater pH increased irregularly just above 7 Cambrian Period, approaching modern average values most recent several millions years. Calcite saturation state decreasing age. Both calcite trends exhibited cyclic overprint environmental conditions. Dissolved sulfate changed variations accretion rates redox conditions, whereas potassium little variation concentration. Using our “standard” results for basis series sensitivity experiments, we vary ventilation rate global ocean, quantify resulting terms processes such net primary production, burial oxidation, pyrite weathering, reduction. use preliminary discuss how affect turn exert sulfur, carbon, systems. postulate periods slow plate rates, associated lower vigorous deep water formation, cooler, drier climatic greater poleward gradients are more likely strong thermohaline circulation, thus “enhanced” mixing. Conversely, higher temperatures equable gradients, sea levels extensive inundation, would coincident times mixing ocean. It important recognize scale depends tectonic (controlling chemical temperature) nutrient supply, productivity, circulation. key elucidating lies an understanding evolution, which leads climate, level, distribution landmasses sedimentary environments they host, circulation