COPSE: A new model of biogeochemical cycling over Phanerozoic time

Clicks: 2
ID: 292502
2004
Free PDF
Article Quality & Performance Metrics
Overall Quality
Not rated
Combines reader engagement with the AI quality analysis. This article has not been analysed, so there is no overall score — reader engagement is measured and shown alongside.
AI Quality Assessment
Not analyzed
Readership in this journal
Steady

Ranked #535 of 8,486 articles by views in american journal of science

Most read Least read

Bar heights use a square-root scale. Only the 120 most-read articles are drawn; the journal has 8,486 in total.

Mint this article as an NFT
Not yet minted

Create a permanent, verifiable on-chain record of this article on the Scimatic Network. The NFT is held in your Journament account, and you can withdraw it to your own wallet at any time.

5 SUSD one-off · no wallet required
Sign in to mint
Abstract
We present a new model of biogeochemical cycling over Phanerozoic time. This work couples a feedback-based model of atmospheric O~2~ and ocean nutrients (Lenton and Watson, 2000a, 2000b) with a geochemical carbon cycle model (Berner, 1991, 1994), a simple sulfur cycle, and additional components. The resulting COPSE model (Carbon-Oxygen-Phosphorus-Sulfur-Evolution) represents the co-evolution of biotic and abiotic components of the Earth system, in that it couples interactive and evolving terrestrial and marine biota to geochemical and tectonic processes. The model is forced with geological and evolutionary forcings and time-dependent solar insolation. The baseline model succeeds in giving simultaneous predictions of atmospheric O~2~, CO~2~, global temperature, ocean composition, δ^13^C and δ^34^S that are in reasonable agreement with available data and suggested constraints. The behavior of the coupled model is qualitatively different to single cycle models. While atmospheric *p*CO~2~ (CO~2~ partial pressure) predictions are mostly determined by the model forcings and the response of silicate weathering rate to *p*CO~2~ and temperature, multiple negative feedback processes and coupling of the C, O, P and S cycles are necessary for regulating *p*O~2~ while allowing δ^13^C changes of sufficient amplitude to match the record. The results support a *p*O~2~ dependency of oxidative weathering of reduced carbon and sulfur, which raises early Paleozoic *p*O~2~ above the estimated requirement of Cambrian fauna and prevents unrealistically large δ^34^S variation. They do not support a strong anoxia dependency of the C:P burial ratio of marine organic matter (Van Cappellen and Ingall, 1994, 1996) because this dependency raises early Paleozoic δ^13^C and organic carbon burial rates too high. The dependency of terrestrial primary productivity on *p*O~2~ also contributes to oxygen regulation. An intermediate strength oxygen fire feedback on terrestrial biomass, which gives a *p*O~2~ upper limit of ∼1.6PAL (present atmospheric level) or 30 volume percent, provides the best combined *p*O~2~ and δ^13^C predictions. Sulfur cycle coupling contributes critically to lowering the Permo-Carboniferous *p*CO~2~ and temperature minimum. The results support an inverse dependency of pyrite sulfur burial on *p*O~2~ (for example, Berner and Canfield, 1989), which contributes to the shuttling of oxygen back and forth between carbonate carbon and gypsum sulfur. A *p*O~2~ dependency of photosynthetic carbon isotope fractionation (Berner and others, 2000; Beerling and others, 2002) is important for producing sufficient magnitude of δ^13^C variation. However, our results do not support an oxygen dependency of sulfur isotope fractionation in pyrite formation (Berner and others, 2000) because it generates unrealistically small variations in δ^34^S. In the Early Paleozoic, COPSE predicts *p*O~2~=0.2--0.6PAL and *p*CO~2~\>10PAL, with high oceanic \[PO~4~^3-^\] and low \[SO~4~^=^\]. Land plant evolution caused a 'phase change' in the Earth system by increasing weathering rates and shifting some organic burial to land. This change resulted in a major drop in *p*CO~2~ to 3 to 4PAL and a rise in *p*O~2~ to ∼1.5PAL in the Permo-Carboniferous, with temperatures below present, ocean variables nearer present concentrations, and PO~4~:NO~3~ regulated closer to Redfield ratio. A second O~2~ peak of similar or slightly greater magnitude appears in the mid-Cretaceous, before a descent towards PAL. Mesozoic CO~2~ is in the range 3 to 7PAL, descending toward PAL in the Cretaceous and Cenozoic.
Reference Key
openalex_W2140479142 Use this key to autocite in the manuscript while using SciMatic Manuscript Manager or Thesis Manager
Authors Noam Bergman
Journal american journal of science
Year 2004
DOI
10.2475/ajs.304.5.397
URL
https://ajs.scholasticahq.com/article/61725.pdf
Keywords Keywords not found

Citations

No citations found. To add a citation, contact the admin at info@scimatic.org

Comments

No comments yet. Be the first to comment on this article.