scholarly journals A diurnal carbon engine explains 13C-enriched carbonates without increasing the global production of oxygen

2019 ◽  
Vol 116 (49) ◽  
pp. 24433-24439 ◽  
Author(s):  
Emily C. Geyman ◽  
Adam C. Maloof
Keyword(s):  
Organic Carbon ◽  
Carbon Cycle ◽  
Shallow Water ◽  
Dissolved Inorganic Carbon ◽  
The Past ◽  
Carbon Isotopic ◽  
Oxygen Paradox ◽  
Carbon Burial ◽  
Continental Shelves ◽  
Organic Carbon Burial

In the past 3 billion years, significant volumes of carbonate with high carbon-isotopic (δ13C) values accumulated on shallow continental shelves. These deposits frequently are interpreted as records of elevated global organic carbon burial. However, through the stoichiometry of primary production, organic carbon burial releases a proportional amount of O2, predicting unrealistic rises in atmospheric pO2 during the 1 to 100 million year-long positive δ13C excursions that punctuate the geological record. This carbon–oxygen paradox assumes that the δ13C of shallow water carbonates reflects the δ13C of global seawater-dissolved inorganic carbon (DIC). However, the δ13C of modern shallow-water carbonate sediment is higher than expected for calcite or aragonite precipitating from seawater. We explain elevated δ13C in shallow carbonates with a diurnal carbon cycle engine, where daily transfer of carbon between organic and inorganic reservoirs forces coupled changes in carbonate saturation (ΩA) and δ13C of DIC. This engine maintains a carbon-cycle hysteresis that is most amplified in shallow, sluggishly mixed waters with high rates of photosynthesis, and provides a simple mechanism for the observed δ13C-decoupling between global seawater DIC and shallow carbonate, without burying organic matter or generating O2.

scholarly journals Ocean Carbon Storage across the middle Miocene: a new interpretation for the Monterey Event

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
S. M. Sosdian ◽  
T. L. Babila ◽  
R. Greenop ◽  
G. L. Foster ◽  
C. H. Lear
Keyword(s):  
Organic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Surface Ocean ◽  
Carbon Burial ◽  
Continental Shelves ◽  
Organic Carbon Burial ◽  
Global Cooling ◽  
New Interpretation ◽  
Ocean Carbon ◽  
Climate Transition

AbstractThe Miocene Climatic Optimum (MCO, 14–17 Ma) was ~3–4 °C warmer than present, similar to estimates for 2100. Coincident with the MCO is the Monterey positive carbon isotope (δ13C) excursion, with oceans more depleted in 12C relative to 13C than any time in the past 50 Myrs. The long-standing Monterey Hypothesis uses this excursion to invoke massive marine organic carbon burial and draw-down of atmospheric CO2 as a cause for the subsequent Miocene Climate Transition and Antarctic glaciation. However, this hypothesis cannot explain the multi-Myr lag between the δ13C excursion and global cooling. We use planktic foraminiferal B/Ca, δ11B, δ13C, and Mg/Ca to reconstruct surface ocean carbonate chemistry and temperature. We propose that the MCO was associated with elevated oceanic dissolved inorganic carbon caused by volcanic degassing, global warming, and sea-level rise. A key negative feedback of this warm climate was the organic carbon burial on drowned continental shelves.

scholarly journals The carbon cycle and associated redox processes through time

2006 ◽  
Vol 361 (1470) ◽  
pp. 931-950 ◽  
Author(s):  
John M Hayes ◽  
Jacob R Waldbauer
Keyword(s):  
Organic Carbon ◽  
Carbon Cycle ◽  
Organic Materials ◽  
Methanogenic Bacteria ◽  
Carbonate Minerals ◽  
Carbon Isotopic ◽  
Carbon Burial ◽  
Organic Carbon Burial ◽  
Oxidizing Power ◽  
Sedimentary Carbonate

Earth's biogeochemical cycle of carbon delivers both limestones and organic materials to the crust. In numerous, biologically catalysed redox reactions, hydrogen, sulphur, iron, and oxygen serve prominently as electron donors and acceptors. The progress of these reactions can be reconstructed from records of variations in the abundance of 13 C in sedimentary carbonate minerals and organic materials. Because the crust is always receiving new CO 2 from the mantle and a portion of it is being reduced by photoautotrophs, the carbon cycle has continuously released oxidizing power. Most of it is represented by Fe 3+ that has accumulated in the crust or been returned to the mantle via subduction. Less than 3% of the estimated, integrated production of oxidizing power since 3.8 Gyr ago is represented by O 2 in the atmosphere and dissolved in seawater. The balance is represented by sulphate. The accumulation of oxidizing power can be estimated from budgets summarizing inputs of mantle carbon and rates of organic-carbon burial, but levels of O 2 are only weakly and indirectly coupled to those phenomena and thus to carbon-isotopic records. Elevated abundances of 13 C in carbonate minerals ca 2.3 Gyr old, in particular, are here interpreted as indicating the importance of methanogenic bacteria in sediments rather than increased burial of organic carbon.

scholarly journals Reduced carbon cycle resilience across the Palaeocene–Eocene Thermal Maximum

2018 ◽  
Vol 14 (10) ◽  
pp. 1515-1527 ◽  
Author(s):  
David I. Armstrong McKay ◽  
Timothy M. Lenton
Keyword(s):  
Organic Carbon ◽  
Carbon Cycle ◽  
Deep Ocean ◽  
Tipping Point ◽  
Tipping Points ◽  
Carbon Burial ◽  
Thermal Maximum ◽  
Organic Carbon Burial ◽  
Carbon Release ◽  
Hyperthermal Events

Abstract. Several past episodes of rapid carbon cycle and climate change are hypothesised to be the result of the Earth system reaching a tipping point beyond which an abrupt transition to a new state occurs. At the Palaeocene–Eocene Thermal Maximum (PETM) at ∼56 Ma and at subsequent hyperthermal events, hypothesised tipping points involve the abrupt transfer of carbon from surface reservoirs to the atmosphere. Theory suggests that tipping points in complex dynamical systems should be preceded by critical slowing down of their dynamics, including increasing temporal autocorrelation and variability. However, reliably detecting these indicators in palaeorecords is challenging, with issues of data quality, false positives, and parameter selection potentially affecting reliability. Here we show that in a sufficiently long, high-resolution palaeorecord there is consistent evidence of destabilisation of the carbon cycle in the ∼1.5 Myr prior to the PETM, elevated carbon cycle and climate instability following both the PETM and Eocene Thermal Maximum 2 (ETM2), and different drivers of carbon cycle dynamics preceding the PETM and ETM2 events. Our results indicate a loss of “resilience” (weakened stabilising negative feedbacks and greater sensitivity to small shocks) in the carbon cycle before the PETM and in the carbon–climate system following it. This pre-PETM carbon cycle destabilisation may reflect gradual forcing by the contemporaneous North Atlantic Volcanic Province eruptions, with volcanism-driven warming potentially weakening the organic carbon burial feedback. Our results are consistent with but cannot prove the existence of a tipping point for abrupt carbon release, e.g. from methane hydrate or terrestrial organic carbon reservoirs, whereas we find no support for a tipping point in deep ocean temperature.

Organic carbon burial in Chinese lakes over the past 150 years

2017 ◽  
Vol 438 ◽  
pp. 94-103 ◽  
Author(s):  
Fengju Zhang ◽  
Shuchun Yao ◽  
Bin Xue ◽  
Xixi Lu ◽  
Zhifan Gui
Keyword(s):  
Organic Carbon ◽  
The Past ◽  
Carbon Burial ◽  
Organic Carbon Burial

scholarly journals Organic carbon burial forcing of the carbon cycle from Himalayan erosion

Nature ◽  
10.1038/36324 ◽  
1997 ◽  
Vol 390 (6655) ◽  
pp. 65-67 ◽  
Author(s):  
Christian France-Lanord ◽  
Louis A. Derry
Keyword(s):  
Organic Carbon ◽  
Carbon Cycle ◽  
Carbon Burial ◽  
Organic Carbon Burial

What Controls Atmospheric Oxygen Concentrations?

2017 ◽  
Author(s):  
Donald Eugene Canfield
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Black Sea ◽  
Atmospheric Oxygen ◽  
Fundamental Question ◽  
The Black Sea ◽  
Microbial Process ◽  
The Past ◽  
Carbon Burial ◽  
Organic Carbon Burial

This chapter deals with the fundamental question of why there is oxygen in the atmosphere at all. It seeks to identify the main processes controlling the oxygen concentration. Plants and cyanobacteria produce the oxygen, but it accumulates only because some of the original photosynthetically produced organic matter is buried and preserved in sediments. Another oxygen source is an anaerobic microbial process called sulfate reduction that respires organic matter using sulfate and produces sulfide. This process is quite common in nature but are most prominent in relatively isolated basins like the Black Sea, and in most marine sediments at depths where oxygen has been consumed by respiration. If there is iron around, the sulfide reacts with the iron, forming a mineral called pyrite. While organic carbon burial has been the main oxygen source to the atmosphere over the past several hundred million years, for some intervals further back in time, pyrite burial may well have dominated as an oxygen source.

scholarly journals Spatio-temporal patterns of organic carbon burial in the sediment of Lake Erhai in China during the past 100 years

2019 ◽  
Vol 31 (1) ◽  
pp. 282-292
Author(s):  
LIU Huiji ◽  
◽  
LIU Enfeng ◽  
YU Zhenzhen ◽  
ZHANG Enlou ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Temporal Patterns ◽  
The Past ◽  
Carbon Burial ◽  
Organic Carbon Burial ◽  
Lake Erhai ◽  
Spatio Temporal

scholarly journals Carbon isotope evidence for large methane emissions to the Proterozoic atmosphere

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Pierre Cadeau ◽  
Didier Jézéquel ◽  
Christophe Leboulanger ◽  
Eric Fouilland ◽  
Emilie Le Floc’h ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Carbon Cycle ◽  
Carbon Isotope ◽  
Methane Emissions ◽  
Unique Combination ◽  
Isotopic Signatures ◽  
The Earth ◽  
Carbon Burial ◽  
Organic Carbon Burial ◽  
Isotope Evidence

Abstract The Proterozoic Era records two periods of abundant positive carbon isotope excursions (CIEs), conventionally interpreted as resulting from increased organic carbon burial and leading to Earth’s surface oxygenation. As strong spatial variations in the amplitude and duration of these excursions are uncovered, this interpretation is challenged. Here, by studying the carbon cycle in the Dziani Dzaha Lake, we propose that they could be due to regionally variable methane emissions to the atmosphere. This lake presents carbon isotope signatures deviated by ~  + 12‰ compared to the modern ocean and shares a unique combination of analogies with putative Proterozoic lakes, interior seas or restricted epireic seas. A simple box model of its Carbon cycle demonstrates that its current isotopic signatures are due to high primary productivity, efficiently mineralized by methanogenesis, and to subsequent methane emissions to the atmosphere. By analogy, these results might allow the reinterpretation of some positive CIEs as at least partly due to regionally large methane emissions. This supports the view that methane may have been a major greenhouse gas during the Proterozoic Era, keeping the Earth from major glaciations, especially during periods of positive CIEs, when increased organic carbon burial would have drowned down atmospheric CO2.

scholarly journals Oceanic Changes Correlate with Methane Seepage

Eos ◽  
2020 ◽  
Vol 101 ◽  
Author(s):  
Hannah Thomasy
Keyword(s):  
Organic Carbon ◽  
Sea Level ◽  
The Past ◽  
Methane Seepage ◽  
Carbon Burial ◽  
Organic Carbon Burial

Changes in sea level and organic carbon burial may have affected seafloor methane seepage over the past 150 million years.

Sign in / Sign up

Export Citation Format

Share Document