Snowball Earth prevention by dissolved organic carbon remineralization

Peltier, W. R.; Liu, Yonggang; Crowley, John W.

doi:10.1038/nature06354

Cited by 100 publications

(119 citation statements)

References 43 publications

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“…A temperature near 0 • C is higher than predicted in the current snowball model and inconsistent with most GCM simulations of snowball Earth conditions . This temperature is compatible with temperature estimates of the variants on the snowball Earth including the slushball models Peltier et al, 2007). The periglacial diapirs and involutions we observe could form within an active layer or degrading permafrost conditions indicating that freeze-thaw or melting may have occurred to several meters depth.…”

Section: Implications For Snowball Earth Hypothesissupporting

confidence: 73%

New constraints on equatorial temperatures during a Late Neoproterozoic snowball Earth glaciation

Ewing

Eisenman

Lamb

et al. 2014

Earth and Planetary Science Letters

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Intense glaciation during the end of Cryogenian time (∼635 million years ago) marks the coldest climate state in Earth history -a time when glacial deposits accumulated at low, tropical paleolatitudes. The leading idea to explain these deposits, the snowball Earth hypothesis, predicts globally frozen surface conditions and subfreezing temperatures, with global climate models placing surface temperatures in the tropics between −20 • C and −60 • C. However, precise paleosurface temperatures based upon geologic constraints have remained elusive and the global severity of the glaciation undetermined. Here we make new geologic observations of tropical periglacial, aeolian and fluvial sedimentary structures formed during the end-Cryogenian, Marinoan glaciation in South Australia; these observations allow us to constrain ancient surface temperatures. We find periglacial sand wedges and associated deformation suggest that ground temperatures were sufficiently warm to allow for ductile deformation of a sandy regolith. The wide range of deformation structures likely indicate the presence of a paleoactive layer that penetrated 2-4 m below the ground surface. These observations, paired with a model of ground temperature forced by solar insolation, constrain the local mean annual surface temperature to within a few degrees of freezing. This temperature constraint matches well with our observations of fluvial deposits, which require temperatures sufficiently warm for surface runoff. Although this estimate coincides with one of the coldest near sea-level tropical temperatures in Earth history, if these structures represent peak Marinaon glacial conditions, they do not support the persistent deep freeze of the snowball Earth hypothesis. Rather, surface temperatures near 0 • C allow for regions of seasonal surface melting, atmosphere-ocean coupling and possible tropical refugia for early metazoans. If instead these structures formed during glacial onset or deglaciation, then they have implications for the timescale and character for the transition into or out of a snowball state.

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Section: Implications For Snowball Earth Hypothesissupporting

confidence: 73%

New constraints on equatorial temperatures during a Late Neoproterozoic snowball Earth glaciation

Ewing

Eisenman

Lamb

et al. 2014

Earth and Planetary Science Letters

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“…S1C). Our modeling is not intended to dismiss the possible significance of diagenesis in generating the carbonate 18 O record. Rather, we carefully propose that some of the coupled changes between the 13 C and 18 O record could have resulted from the natural operation of the carbon cycle.…”

Section: Resultsmentioning

confidence: 99%

“…The end result is high atmospheric methane concentrations. Greenhouse warming from the methane increases surface temperature and melts glacial ice, which combine to produce a negative 18 O anomaly in precipitated carbonates. The higher temperatures also accelerate the weathering of continental rocks, drawing down atmospheric CO 2 .…”

Section: Modelmentioning

confidence: 99%

“…While receiving wide attention (4,6,16,18), it is unclear with this model how the oxidation events are triggered, and the large isotope excursions seemingly require more oxidant than can be supplied by the atmosphere and ocean system (19). Therefore, we present a unique carbon cycle model which accounts for the amplitude and phasing of the late Neoproterozoic carbonate and inorganic carbon 13 C records as observed through many of these anomalies, and shows that at least a part of the 18 O excursions may also have a nondiagenetic origin.…”

mentioning

confidence: 99%

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Towards a quantitative understanding of the late Neoproterozoic carbon cycle

Bjerrum

Canfield

2011

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

121

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The cycles of carbon and oxygen at the Earth surface are intimately linked, where the burial of organic carbon into sediments represents a source of oxygen to the surface environment. This coupling is typically quantified through the isotope records of organic and inorganic carbon. Yet, the late Neoproterozoic Eon, the time when animals first evolved, experienced wild isotope fluctuations which do not conform to our normal understanding of the carbon cycle and carbon-oxygen coupling. We interpret these fluctuations with a new carbon cycle model and demonstrate that all of the main features of the carbonate and organic carbon isotope record can be explained by the release of methane hydrates from an anoxic dissolved organic carbon-rich ocean into an atmosphere containing oxygen levels considerably less than today.carbon isotope excursion | carbon monoxide | Shuram-Wonoka anomaly | earth evolution | atmospheric chemistry T he Neoproterozoic Eon was one of the most dynamic, yet enigmatic, times in Earth history. The Eon saw the breakup of super continent Rodinia and was punctuated by several glacial episodes, some of which were global in extent (1). The Eon saw the evolution and expansion of the first animals on Earth (2), as well as a rise in atmospheric oxygen and a major oxygenation of the deep ocean (3, 4). The isotopic composition* of carbonate (δ 13 C IC ) in sedimentary rocks reveals some of the largest isotope fluctuations in marine dissolved inorganic carbon (DIC) in Earth history (e.g., 4-6). Such isotope fluctuations are considered to reflect dynamics in the carbon cycle, and they have been used to reconstruct the history of atmospheric oxygen (e.g., 7, 8).The Neoproterozoic δ 13 C IC record, however, reveals excursions to less than mantle values (< − 5‰), and the assumed input value to the oceans (5, 9) ( Fig. 1). Prolonged negative δ 13 C IC excursions such as these cannot be explained by our normal understanding of the carbon cycle (e.g., 10, 11). While a diagenetic origin has been advocated to explain these excursions (12, 13), we will show that the major features of the carbon isotope records are consistent with a seawater origin through the action of the carbon cycle.Indeed, a nondiagenetic origin for the carbon isotope excursion is supported by the fact that in individual regions, an excursion may be observed over 100's of kilometers, mappable to the same stratigraphic horizon, and with isotope trends independent of sediment lithology (e.g., 14-16). The lateral extent and stratigraphic consistency of these excursions is difficult to reconcile with a diagenetic origin. Furthermore, modeling shows that the extent of isotopic alteration during diagenesis is highly dependant on the mineralogy of both the initial and the altered sediment (12). Isotope trends, however, transcend these differences (e.g., 6, 14, 17), further arguing against a diagenetic origin for the isotope signals.Many of the large Neoproterozoic isotope excursions display a relationship between the 18 O and 13 C of carbonate, which is...

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“…The controls on ocean DOC production and remineralization are therefore of primary importance in regulating the global carbon cycle. Despite the importance of DOC to biogeochemical cycles, and its potential for impacting global climate [Peltier et al, 2007;Ridgwell, 2011;Sexton et al, 2011], explicit controls governing the cycling of marine DOC are not fully understood.…”

Section: Introductionmentioning

confidence: 99%

Pacific carbon cycling constrained by organic matter size, age and composition relationships

et al. 2016

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Marine dissolved organic carbon (DOC) is a major global carbon reservoir, yet its cycling remains poorly understood. Previous work suggests that DOC molecular size and chemical composition can significantly affect its bioavailability. Thus, DOC size and composition may control DOC cycling and radiocarbon age (via Δ 14 C). Here we show that DOC molecular size is correlated to DOC Δ 14 C in the Pacific Ocean. Our results, based on a series of increasing molecular size fractions from three depths in the Pacific, show increasing DOC Δ 14 C with increasing molecular size. We use a size-age distribution model to predict the DOC and Δ 14 C of ultrafiltered DOC. The model predicts both large and small surface DOC with high Δ 14 C and a narrow range (200-500 Da) of low Δ 14 C DOC. Deep model offsets suggest different size distributions and/or Δ 14 C sources at 670-915 m. Our results suggest that molecular size and composition are linked to DOC reactivity and storage in the ocean.

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Snowball Earth prevention by dissolved organic carbon remineralization

Cited by 100 publications

References 43 publications

New constraints on equatorial temperatures during a Late Neoproterozoic snowball Earth glaciation

New constraints on equatorial temperatures during a Late Neoproterozoic snowball Earth glaciation

Towards a quantitative understanding of the late Neoproterozoic carbon cycle

Pacific carbon cycling constrained by organic matter size, age and composition relationships

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