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.

scholarly journals Reduced Carbon Cycle Resilience across the Palaeocene-Eocene Thermal Maximum

2018 ◽  
Author(s):  
David I. Armstrong McKay ◽  
Timothy M. Lenton
Keyword(s):  
Carbon Cycle ◽  
North Atlantic ◽  
Deep Ocean ◽  
Tipping Point ◽  
Tipping Points ◽  
Slowing Down ◽  
Thermal Maximum ◽  
Carbon Release ◽  
Hyperthermal Events ◽  
Negative Feedbacks

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) ~ 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 My prior to the PETM, elevated carbon cycle and climate instability following both the PETM and Eocene Thermal Maximum 2 (ETM2), and differing carbon cycle dynamics preceding the PETM and ETM2. 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. 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.

scholarly journals Thermogenic carbon release from the Central Atlantic magmatic province caused major end-Triassic carbon cycle perturbations

2020 ◽  
Vol 117 (22) ◽  
pp. 11968-11974 ◽  
Author(s):  
Thea H. Heimdal ◽  
Morgan T. Jones ◽  
Henrik. H. Svensen
Keyword(s):  
Carbon Cycle ◽  
Carbon Sources ◽  
Carbon Burial ◽  
Central Atlantic Magmatic Province ◽  
Organic Carbon Burial ◽  
Terrestrial Sediments ◽  
Carbon Release ◽  
Sediment Carbon ◽  
Central Atlantic ◽  
Contact Aureoles

The Central Atlantic magmatic province (CAMP), the end-Triassic mass extinction (ETE), and associated major carbon cycle perturbations occurred synchronously around the Triassic–Jurassic (T–J) boundary (201 Ma). Negative carbon isotope excursions (CIEs) recorded in marine and terrestrial sediments attest to the input of isotopically light carbon, although the carbon sources remain debated. Here, we explore the effects of mantle-derived and thermogenic carbon released from the emplacement of CAMP using the long-term ocean–atmosphere–sediment carbon cycle reservoir (LOSCAR) model. We have tested a detailed emission scenario grounded by numerous complementary boundary conditions, aiming to model the full extent of the carbon cycle perturbations around the T–J boundary. These include three negative CIEs (i.e., Marshi/Precursor, Spelae/Initial, Tilmanni/Main) with sharp positive CIEs in between. We show that a total of ∼24,000 Gt C (including ∼12,000 Gt thermogenic C) replicates the proxy data. These results indicate that thermogenic carbon generated from the contact aureoles around CAMP sills represents a credible source for the negative CIEs. An extremely isotopically depleted carbon source, such as marine methane clathrates, is therefore not required. Furthermore, we also find that significant organic carbon burial, in addition to silicate weathering, is necessary to account for the positive δ13C intervals following the negative CIEs.

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

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 Warm plankton soup and red herrings: calcareous nannoplankton cellular communities and the Palaeocene–Eocene Thermal Maximum

2018 ◽  
Vol 376 (2130) ◽  
pp. 20170075 ◽  
Author(s):  
Samantha J. Gibbs ◽  
Rosie M. Sheward ◽  
Paul R. Bown ◽  
Alex J. Poulton ◽  
Sarah A. Alvarez
Keyword(s):  
Global Warming ◽  
Organic Carbon ◽  
Inorganic Carbon ◽  
Climate Feedback ◽  
Short Term ◽  
Cell Size Distribution ◽  
Carbon Burial ◽  
Thermal Maximum ◽  
Carbon Transfer ◽  
Organic Carbon Burial

Past global warming events such as the Palaeocene–Eocene Thermal Maximum (PETM—56 Ma) are attributed to the release of vast amounts of carbon into the ocean, atmosphere and biosphere with recovery ascribed to a combination of silicate weathering and organic carbon burial. The phytoplanktonic nannoplankton are major contributors of organic and inorganic carbon but their role in this recovery process remains poorly understood and complicated by their contribution to marine calcification. Biocalcification is implicated not only in long-term carbon burial but also both short-term positive and negative climatic feedbacks associated with seawater buffering and responses to ocean acidification. Here, we use exceptional records of preserved fossil coccospheres to reconstruct cell size distribution, biomass production (particulate organic carbon, POC) and (particulate) inorganic carbon (PIC) yields of three contrasting nannoplankton communities (Bass River—outer shelf, Maud Rise—uppermost bathyal, Shatsky Rise—open ocean) through the PETM onset and recovery. Each of the sites shows contrasting community responses across the PETM as a function of their taxic composition and total community biomass. Our results indicate that nannoplankton PIC:POC had no role in short-term climate feedback and, as such, their importance as a source of CO 2 to the environment is a red herring. It is nevertheless likely that shifts to greater numbers of smaller cells at the shelf site in particular led to greater carbon transfer efficiency, and that nannoplankton productivity and export across the shelves had a significant modulating effect on carbon sequestration during the PETM recovery. This article is part of a discussion meeting issue ‘Hyperthermals: rapid and extreme global warming in our geological past’.

Modelling the impact of pulsed CAMP volcanism on pCO2 and δ13C across the Triassic–Jurassic transition

2015 ◽  
Vol 153 (2) ◽  
pp. 252-270 ◽  
Author(s):  
AVIV BACHAN ◽  
JONATHAN L. PAYNE
Keyword(s):  
Carbon Cycle ◽  
Carbon Burial ◽  
Central Atlantic Magmatic Province ◽  
Organic Carbon Burial ◽  
Carbon Release ◽  
Carbon Injection ◽  
Delayed Recovery ◽  
Central Atlantic ◽  
The Impact ◽  
Age Constraints

AbstractA sharp negative δ13C excursion coincides with the end-Triassic mass extinction. This is followed by a protracted interval of 13C enrichment. These isotopic events occurred simultaneously with the emplacement of the Central Atlantic Magmatic Province (CAMP). Here we use a carbon cycle box model to explore the effects of episodic carbon release – constrained by recently developed high-resolution chronology – on atmospheric pCO2, ocean chemistry and the δ13C of the ocean–atmosphere carbon pool. Our results are consistent with previous modelling efforts in suggesting that the sharp negative δ13C excursion and acidification event associated with the extinction are best explained by the rapid release (<20 ka) of highly 13C-depleted carbon (−70‰). However, our model also indicates that the likely short duration of the excursion requires organic carbon burial to have closely followed carbon injection. The age within the Hettangian of the large positive δ13C excursion which follows is currently uncertain. If early Hettangian in age, then our modelling indicates that the interval of 13C enrichment was closely associated with the volcanic CO2 pulses and pCO2 peaks. If late Hettangian in age, then the 13C enrichment must have lagged the carbon input substantially (by hundreds of thousands of years) and was associated with CO2 drawdown and over-cooling. Our modelling highlights the need for improved age constraints on Hettangian stratigraphic sections in order to test between two distinct and contrasting possibilities: continuing carbon cycle instability due to recurrent perturbations from CAMP activity or a delayed recovery arising from internal biosphere dynamics.

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 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 Past climate variations recorded in needle-like aragonites correlate with organic carbon burial efficiency as revealed by lake sediments in Croatia

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ivan Razum ◽  
Petra Bajo ◽  
Dea Brunović ◽  
Nikolina Ilijanić ◽  
Ozren Hasan ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Stable Carbon Isotope ◽  
Climate Variations ◽  
Before Present ◽  
Stable Carbon ◽  
Climate Trends ◽  
Geochemical Proxies ◽  
Carbon Burial ◽  
Organic Carbon Burial ◽  
Burial Efficiency

AbstractThe drivers of organic carbon (OC) burial efficiency are still poorly understood despite their key role in reliable projections of future climate trends. Here, we provide insights on this issue by presenting a paleoclimate time series of sediments, including the OC contents, from Lake Veliko jezero, Croatia. The Sr/Ca ratios of the bulk sediment are mainly derived from the strontium (Sr) and calcium (Ca) concentrations of needle-like aragonite in Core M1-A and used as paleotemperature and paleohydrology indicators. Four major and six minor cold and dry events were detected in the interval from 8.3 to 2.6 calibrated kilo anno before present (cal ka BP). The combined assessment of Sr/Ca ratios, OC content, carbon/nitrogen (C/N) ratios, stable carbon isotope (δ13C) ratios, and modeled geochemical proxies for paleoredox conditions and aeolian input revealed that cold and dry climate states promoted anoxic conditions in the lake, thereby enhancing organic matter preservation and increasing the OC burial efficiency. Our study shows that the projected future increase in temperature might play an important role in the OC burial efficiency of meromictic lakes.

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