Abundant Early Palaeogene marine gas hydrates despite warm deep-ocean temperatures

Gu, Guangsheng; Dickens, Gerald R.; Bhatnagar, Gaurav; Colwell, Frederick S.; Hirasaki, George J.; Chapman, Walter G.

doi:10.1038/ngeo1301

Cited by 43 publications

(35 citation statements)

References 24 publications

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“…These variations in POC deposition have a much stronger impact on the hydrate inventory than the temperature does. This is consistent with the recent finding of Gu et al [2011] The sensitivity of the hydrate inventory can also be seen in the model response to changes in the labile fraction of the sedimenting POC (Figure 34c). In practice, the respiration zone is thin enough that the POC is not often limited by depletion of the labile POC fraction, so the labile fraction acts like a scaling of the apparent bulk POC degradation rate constant.…”

Section: Sensitivity To Pocsupporting

confidence: 81%

Integrating Natural Gas Hydrates in the Global Carbon Cycle

Archer¹,

Buffett²

2011

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We produced a two-dimensional geological time-and basin-scale model of the sedimentary margin in passive and active settings, for the simulation of the deep sedimentary methane cycle including hydrate formation. Simulation of geochemical data required development of parameterizations for bubble transport in the sediment column, and for the impact of the heterogeneity in the sediment pore fluid flow field, which represent new directions in modeling methane hydrates. The model is somewhat less sensitive to changes in ocean temperature than our previous 1-D model, due to the different methane transport mechanisms in the two codes (pore fluid flow vs. bubble migration). The model is very sensitive to reasonable changes in organic carbon deposition through geologic time, and to details of how the bubbles migrate, in particular how efficiently they are trapped as they rise through undersaturated or oxidizing chemical conditions and the hydrate stability zone. The active margin configuration reproduces the elevated hydrate saturations observed in accretionary wedges such as the Cascadia Margin, but predicts a decrease in the methane inventory per meter of coastline relative to a comparable passive margin case, and a decrease in the hydrate inventory with an increase in the plate subduction rate.

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Section: Sensitivity To Pocsupporting

confidence: 81%

Integrating Natural Gas Hydrates in the Global Carbon Cycle

Archer¹,

Buffett²

2011

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“…However, these ideas have been little discussed in relation to the warm Eocene oceans or other warm intervals of the past. Gu et al [40] proposed that a warmer ocean would increase rates of methanogenesis in seafloor sediments, thus providing a source for the isotopically light carbon released during Eocene hyperthermals. However, a warmer ocean would presumably also affect rates of aerobic respiration of sinking organic matter.…”

Section: The Metabolic Hypothesis and The Q 10 Relationshipmentioning

confidence: 99%

Warm ocean processes and carbon cycling in the Eocene

John

Pearson

Coxall

et al. 2013

Phil. Trans. R. Soc. A.

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Sea surface and subsurface temperatures over large parts of the ocean during the Eocene epoch (55.5–33.7 Ma) exceeded modern values by several degrees, which must have affected a number of oceanic processes. Here, we focus on the effect of elevated water column temperatures on the efficiency of the biological pump, particularly in relation to carbon and nutrient cycling. We use stable isotope values from exceptionally well-preserved planktonic foraminiferal calcite from Tanzania and Mexico to reconstruct vertical carbon isotope gradients in the upper water column, exploiting the fact that individual species lived and calcified at different depths. The oxygen isotope ratios of different species' tests are used to estimate the temperature of calcification, which we converted to absolute depths using Eocene temperature profiles generated by general circulation models. This approach, along with potential pitfalls, is illustrated using data from modern core-top assemblages from the same area. Our results indicate that, during the Early and Middle Eocene, carbon isotope gradients were steeper (and larger) through the upper thermocline than in the modern ocean. This is consistent with a shallower average depth of organic matter remineralization and supports previously proposed hypotheses that invoke high metabolic rates in a warm Eocene ocean, leading to more efficient recycling of organic matter and reduced burial rates of organic carbon.

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“…However, alternative mechanisms, such as direct radiative forcing due to an increased pCH 4 , and associated indirect effects (26,27,30,31) may overrule this objection. The assumption that early Paleogene methane clathrate reservoirs were too small (84) has recently been discredited (26,85). The idea that the amount of carbon released from methane clathrates would have been insufficient to explain observed shoaling of the carbonate compensation depth (86) has also been criticized (26).…”

Section: Resultsmentioning

confidence: 99%

Temperature and atmospheric CO ₂ concentration estimates through the PETM using triple oxygen isotope analysis of mammalian bioapatite

Gehler¹,

Gingerich

Pack

2016

Proc. Natl. Acad. Sci. U.S.A.

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The Paleocene-Eocene Thermal Maximum (PETM) is a remarkable climatic and environmental event that occurred 56 Ma ago and has importance for understanding possible future climate change. The Paleocene-Eocene transition is marked by a rapid temperature rise contemporaneous with a large negative carbon isotope excursion (CIE). Both the temperature and the isotopic excursion are well-documented by terrestrial and marine proxies. The CIE was the result of a massive release of carbon into the atmosphere. However, the carbon source and quantities of CO 2 and CH 4 greenhouse gases that contributed to global warming are poorly constrained and highly debated. Here we combine an established oxygen isotope paleothermometer with a newly developed triple oxygen isotope paleo-CO 2 barometer. We attempt to quantify the source of greenhouse gases released during the Paleocene-Eocene transition by analyzing bioapatite of terrestrial mammals. Our results are consistent with previous estimates of PETM temperature change and suggest that not only CO 2 but also massive release of seabed methane was the driver for CIE and PETM.PETM | temperature | CO 2 concentration | mammals

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Abundant Early Palaeogene marine gas hydrates despite warm deep-ocean temperatures

Cited by 43 publications

References 24 publications

Integrating Natural Gas Hydrates in the Global Carbon Cycle

Integrating Natural Gas Hydrates in the Global Carbon Cycle

Warm ocean processes and carbon cycling in the Eocene

Temperature and atmospheric CO ₂ concentration estimates through the PETM using triple oxygen isotope analysis of mammalian bioapatite

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Abundant Early Palaeogene marine gas hydrates despite warm deep-ocean temperatures

Cited by 43 publications

References 24 publications

Integrating Natural Gas Hydrates in the Global Carbon Cycle

Integrating Natural Gas Hydrates in the Global Carbon Cycle

Warm ocean processes and carbon cycling in the Eocene

Temperature and atmospheric CO 2 concentration estimates through the PETM using triple oxygen isotope analysis of mammalian bioapatite

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Product

Resources

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Temperature and atmospheric CO ₂ concentration estimates through the PETM using triple oxygen isotope analysis of mammalian bioapatite