Modeling organic carbon burial during sea level rise with reference to the Cretaceous

Abstract

[1] After three decades of research on the correlation between sea level and various proxies, there has been very little quantification of the first-order influence of sea level change on nutrient inventory, marine productivity, and burial of organic carbon. We present a model aimed at quantifying the burial of organic carbon as a function of sea level rise. The biogeochemical model explicitly considers the mean surface area distribution of the Earth as a function of elevation. Also included is dissolved inorganic phosphate (DIP) liberated from coastal sediments during transgression. We quantify how sea level rise of magnitudes inferred for the mid-Cretaceous influences the phosphorus cycle and burial of organic carbon. The burial efficiency is greater on the shelf. Therefore, in the model, the larger shelf area under high sea level results in more efficient burial of marine organic carbon for a given DIP concentration and associated new production of organic matter (NP). With a Late Cretaceous model shelf area the residence time of DIP decreases by 60% relative to the present-day reference. Thus, in the final steady state, DIP and NP in the open ocean are reduced compared to today when the biologically reactive phosphorus (P reac ) fluxes to the ocean from land are held constant. The lower new production reduces the oxygen demand for respiration and results in a significant oxygenation of the global ocean. Finally, the global organic carbon burial decreases by 30% relative to today in the model. This decrease results from feedbacks between the flux of organic carbon to the seafloor and the ratio of organic carbon to P reac in buried sediments. In contrast, during sea level rise, coastal erosion may increase the P reac flux to the ocean by up to $20% relative to today and cause a temporary increase in DIP concentration in the ocean. The resulting increase in organic carbon burial is equivalent to a carbon isotope event of +0.5 to 1%. Larger carbon isotope events can be triggered by sea level rise only when the ocean is sufficiently close to anoxia in the oxygen minimum zone just prior to the sea level rise.

The global marine phosphorus cycle: sensitivity to oceanic circulation

“…As shown by Fig. 10, a 20% increase in reactive P supply from the continents, for example due to coastal erosion linked to sealevel rise (Erbacher et al, 1996;Bjerrum et al, 2006), would be sufficient to increase oceanic primary productivity and cause a major enhancement of POC burial in marine sediments during periods of reduced circulation.…”

“…Consequently, insight into the various forcings and functioning of the marine P cycle is needed to underCorrespondence to: C. P. Slomp (slomp@geo.uu.nl) stand long-term variations in marine biological activity, atmospheric composition and climate (Holland, 1984;Van Cappellen and Ingall, 1996;Petsch and Berner, 1998;Bjerrum and Canfield, 2002). Important forcings include the supply of reactive P from the continents, oceanic circulation and sea level fluctuations (Föllmi, 1996;Compton et al, 2000;Handoh and Lenton, 2003;Wallmann, 2003;Bjerrum et al, 2006).…”

A high-resolution carbon-isotope record of the Turonian stage correlated to a siliciclastic basin fill: Implications for mid-Cretaceous sea-level change

“…Quantitative modelling of carbon burial during sea-level rise can, under certain conditions, simulate limited positive excursions in d 13 C (Bjerrum et al, 2006), but although sea-level rise and organic-C deposition may react to the same forcing, they need not have a direct causal link. Recent studies of Mesozoic and Cenozoic datasets that demonstrate orbital-driven, climatic control of d 13 C fluctuations (Cramer et al, 2003;Pälike et al, 2006;Voigt et al, 2007;Giorgioni et al, 2012) do not interpret direct links with sea-level change.…”

Pleistocene sediment offloading and the global sulfur cycle

“…(b) Calculated shelf area using polynomial fit (Bjerrum et al, 2006) of ETOPO-5 global mean hypsometric curve. bic polynomial fit (Eq.…”

“…bic polynomial fit (Eq. 6, after Bjerrum et al, 2006) of the ETOPO-5 hypsometric curve (National Geophysical Data Center, 1988):…”