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Li M, Bralower TJ, Kump LR, Self-Trail JM, Zachos JC, Rush WD, Robinson MM. Astrochronology of the Paleocene-Eocene Thermal Maximum on the Atlantic Coastal Plain. Nat Commun 2022; 13:5618. [PMID: 36153313 PMCID: PMC9509358 DOI: 10.1038/s41467-022-33390-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Accepted: 09/15/2022] [Indexed: 11/09/2022] Open
Abstract
AbstractThe chronology of the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma) remains disputed, hampering complete understanding of the possible trigger mechanisms of this event. Here we present an astrochronology for the PETM carbon isotope excursion from Howards Tract, Maryland a paleoshelf environment, on the mid-Atlantic Coastal Plain. Statistical evaluation of variations in calcium content and magnetic susceptibility indicates astronomical forcing was involved and the PETM onset lasted about 6 kyr. The astrochronology and Earth system modeling suggest that the PETM onset occurred at an extreme in precession during a maximum in eccentricity, thus favoring high temperatures, indicating that astronomical forcing could have played a role in triggering the event. Ca content data on the paleo-shelf, along with other marine records, support the notion that a carbonate saturation overshoot followed global ocean acidification during the PETM.
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Archaeal lipid biomarker constraints on the Paleocene-Eocene carbon isotope excursion. Nat Commun 2019; 10:4519. [PMID: 31586063 PMCID: PMC6778145 DOI: 10.1038/s41467-019-12553-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Accepted: 09/17/2019] [Indexed: 11/12/2022] Open
Abstract
A negative carbon isotope excursion recorded in terrestrial and marine archives reflects massive carbon emissions into the exogenic carbon reservoir during the Paleocene-Eocene Thermal Maximum. Yet, discrepancies in carbon isotope excursion estimates from different sample types lead to substantial uncertainties in the source, scale, and timing of carbon emissions. Here we show that membrane lipids of marine planktonic archaea reliably record both the carbon isotope excursion and surface ocean warming during the Paleocene-Eocene Thermal Maximum. Novel records of the isotopic composition of crenarchaeol constrain the global carbon isotope excursion magnitude to −4.0 ± 0.4‰, consistent with emission of >3000 Pg C from methane hydrate dissociation or >4400 Pg C for scenarios involving emissions from geothermal heating or oxidation of sedimentary organic matter. A pre-onset excursion in the isotopic composition of crenarchaeol and ocean temperature highlights the susceptibility of the late Paleocene carbon cycle to perturbations and suggests that climate instability preceded the Paleocene-Eocene Thermal Maximum. The Paleocene-Eocene Thermal Maximum (c. 55 million years ago) was a period associated with massive carbon injection into the atmosphere, yet discrepancies in carbon isotope proxy records have led to substantial uncertainties in the source, scale, and timing of carbon emissions. Here, the authors propose that membrane lipids of marine planktonic archaea can reliably record the carbon isotope excursion and surface ocean warming, giving a new constraint for the source and size of the PETM carbon emissions.
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Abstract
Restoration strategies for coral reefs are usually focused on the recovery of bio-physical characteristics. They seldom include an evaluation of the recovery of the socio-ecological and ecosystem services features of coral reef systems. This paper proposes a conceptual framework to address both the socio-ecological system features of coral reefs with the implementation of restoration activity for degraded coral reefs. Such a framework can lead to better societal outcomes from restoration activities while restoring bio-physical, social and ecosystem service features of such systems. We first developed a Socio Ecological System Analysis Framework, which combines the Ostrom Framework for analyzing socio-ecological systems and the Kittinger et al. human dimensions framework of coral reefs socio-ecological systems. We then constructed a Restoration of Coral Reef Framework, based on the most used and recent available coral reef restoration literature. These two frameworks were combined to present a Socio-Ecological Systems & Restoration Coral Reef Framework. These three frameworks can be used as a guide for managers, researchers and decision makers to analyze the needs of coral reef restoration in a way that addresses both socio-economic and ecological objectives to analyze, design, implement and monitor reef restoration programs.
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4
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Schaller MF, Fung MK. The extraterrestrial impact evidence at the Palaeocene-Eocene boundary and sequence of environmental change on the continental shelf. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2018; 376:rsta.2017.0081. [PMID: 30177564 PMCID: PMC6127391 DOI: 10.1098/rsta.2017.0081] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 07/30/2018] [Indexed: 05/06/2023]
Abstract
We have identified clear evidence of an extraterrestrial impact within the onset of the carbon isotope excursion (CIE) that defines the Palaeocene-Eocene (P-E) boundary hyperthermal event (approx. 56 Ma) from several sites on the eastern Atlantic Coastal Plain and offshore. We review and update the state of the evidence for an impact at the P-E boundary, including a K-Ar cooling age of the ejecta that is indistinguishable from the depositional age at the P-E, which establishes the ejecta horizon as an isochronous stratigraphic indicator at the P-E. Immediately above the ejecta peak at the base of the coastal plain Marlboro Clay unit, we identify a sharp increase in charcoal abundance coincident with the previously observed dramatic increase in magnetic nanoparticles of soil pyrogenic origin. We therefore revisit the observed sequence of events through the P-E boundary on the western Atlantic Coastal Plain, showing that an extraterrestrial impact led to wildfires, landscape denudation and deposition of the thick Marlboro Clay, whose base coincides with the spherule horizon and CIE onset. The Sr/Ca ratio of the spherules indicates that the carbon responsible for the onset may be vaporized CaCO3 target rock mixed with isotopically light carbon from the impactor or elsewhere. Crucially, we do not argue that the impact was responsible for the full manifestation of the CIE observed globally (onset to recovery approx. 170 kyr), rather that a rapid onset was triggered by the impact and followed by additional carbon from other processes such as the eruption of the North Atlantic Igneous Province. Such a scenario agrees well with recent modelling work, though it should be revisited more explicitly.This article is part of a discussion meeting issue 'Hyperthermals: rapid and extreme global warming in our geological past'.
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Affiliation(s)
- Morgan F Schaller
- Earth and Environmental Sciences, Rensselaer Polytechnic Institute, Troy, NY, USA
| | - Megan K Fung
- Earth and Environmental Sciences, Rensselaer Polytechnic Institute, Troy, NY, USA
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5
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Turner SK. Constraints on the onset duration of the Paleocene-Eocene Thermal Maximum. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2018; 376:rsta.2017.0082. [PMID: 30177565 PMCID: PMC6127381 DOI: 10.1098/rsta.2017.0082] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 07/25/2018] [Indexed: 05/30/2023]
Abstract
The Paleocene-Eocene Thermal Maximum (PETM, approx. 56 Ma) provides a test case for investigating how the Earth system responds to rapid greenhouse gas-driven warming. However, current rates of carbon emissions are approximately 10 Pg C yr-1, whereas those proposed for the PETM span orders of magnitude-from ≪1 Pg C yr-1 to greater than the anthropogenic rate. Emissions rate estimates for the PETM are hampered by uncertainty over the total mass of PETM carbon released as well as the PETM onset duration. Here, I review constraints on the onset duration of the carbon isotope excursion (CIE) that is characteristic of the event with a focus on carbon cycle model-based attempts that forgo the need for a traditional sedimentary age model. I also review and compare existing PETM carbon input scenarios employing the Earth system model cGENIE and suggest another possibility-that abrupt input of an isotopically depleted carbon source combined with elevated volcanic outgassing over a longer interval can together account for key features of the PETM CIE.This article is part of a discussion meeting issue 'Hyperthermals: rapid and extreme global warming in our geological past'.
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6
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Gutjahr M, Ridgwell A, Sexton PF, Anagnostou E, Pearson PN, Pälike H, Norris RD, Thomas E, Foster GL. Very large release of mostly volcanic carbon during the Palaeocene-Eocene Thermal Maximum. Nature 2018; 548:573-577. [PMID: 28858305 PMCID: PMC5582631 DOI: 10.1038/nature23646] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 07/06/2017] [Indexed: 11/09/2022]
Abstract
The Palaeocene-Eocene Thermal Maximum (PETM) was a global warming event that occurred about 56 million years ago, and is commonly thought to have been driven primarily by the destabilization of carbon from surface sedimentary reservoirs such as methane hydrates. However, it remains controversial whether such reservoirs were indeed the source of the carbon that drove the warming. Resolving this issue is key to understanding the proximal cause of the warming, and to quantifying the roles of triggers versus feedbacks. Here we present boron isotope data-a proxy for seawater pH-that show that the ocean surface pH was persistently low during the PETM. We combine our pH data with a paired carbon isotope record in an Earth system model in order to reconstruct the unfolding carbon-cycle dynamics during the event. We find strong evidence for a much larger (more than 10,000 petagrams)-and, on average, isotopically heavier-carbon source than considered previously. This leads us to identify volcanism associated with the North Atlantic Igneous Province, rather than carbon from a surface reservoir, as the main driver of the PETM. This finding implies that climate-driven amplification of organic carbon feedbacks probably played only a minor part in driving the event. However, we find that enhanced burial of organic matter seems to have been important in eventually sequestering the released carbon and accelerating the recovery of the Earth system.
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Affiliation(s)
- Marcus Gutjahr
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton SO17 1BJ, UK.,GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstrasse 1-3, 24148 Kiel, Germany
| | - Andy Ridgwell
- School of Geographical Sciences, Bristol University, Bristol BS8 1SS, UK.,Department of Earth Sciences, University of California at Riverside, Riverside, California 92521, USA
| | - Philip F Sexton
- School of Environment, Earth and Ecosystem Sciences, The Open University, Milton Keynes MK7 6AA, UK
| | - Eleni Anagnostou
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton SO17 1BJ, UK
| | - Paul N Pearson
- School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3AT, UK
| | - Heiko Pälike
- MARUM, Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany
| | - Richard D Norris
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92037, USA
| | - Ellen Thomas
- Department of Geology and Geophysics, Yale University, New Haven, Connecticut 06520, USA.,Department of Earth and Environmental Sciences, Wesleyan University, Middletown, Connecticut 06459, USA
| | - Gavin L Foster
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton SO17 1BJ, UK
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7
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Cyriac VP, Kodandaramaiah U. Paleoclimate determines diversification patterns in the fossorial snake family Uropeltidae Cuvier, 1829. Mol Phylogenet Evol 2017; 116:97-107. [PMID: 28867076 DOI: 10.1016/j.ympev.2017.08.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Revised: 08/17/2017] [Accepted: 08/24/2017] [Indexed: 11/15/2022]
Abstract
Understanding how and why diversification rates vary across evolutionary time is central to understanding how biodiversity is generated and maintained. Recent mathematical models that allow estimation of diversification rates across time from reconstructed phylogenies have enabled us to make inferences on how biodiversity copes with environmental change. Here, we explore patterns of temporal diversification in Uropeltidae, a diverse fossorial snake family. We generate a time-calibrated phylogenetic hypothesis for Uropeltidae and show a significant correlation between diversification rate and paleotemperature during the Cenozoic. We show that the temporal diversification pattern of this group is punctuated by one rate shift event with a decrease in diversification and turnover rate between ca. 11Ma to present, but there is no strong support for mass extinction events. The analysis indicates higher turnover during periods of drastic climatic fluctuations and reduced diversification rates associated with contraction and fragmentation of forest habitats during the late Miocene. Our study highlights the influence of environmental fluctuations on diversification rates in fossorial taxa such as uropeltids, and raises conservation concerns related to present rate of climate change.
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Affiliation(s)
- Vivek Philip Cyriac
- IISER-TVM Centre for Research and Education in Ecology and Evolution (ICREEE) and School of Biology, Indian Institute of Science Education and Research Thiruvananthapuram, Maruthamala P.O., Vithura, Thiruvananthapuram, Kerala 695551, India.
| | - Ullasa Kodandaramaiah
- IISER-TVM Centre for Research and Education in Ecology and Evolution (ICREEE) and School of Biology, Indian Institute of Science Education and Research Thiruvananthapuram, Maruthamala P.O., Vithura, Thiruvananthapuram, Kerala 695551, India
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8
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van Oppen MJH, Gates RD, Blackall LL, Cantin N, Chakravarti LJ, Chan WY, Cormick C, Crean A, Damjanovic K, Epstein H, Harrison PL, Jones TA, Miller M, Pears RJ, Peplow LM, Raftos DA, Schaffelke B, Stewart K, Torda G, Wachenfeld D, Weeks AR, Putnam HM. Shifting paradigms in restoration of the world's coral reefs. GLOBAL CHANGE BIOLOGY 2017; 23:3437-3448. [PMID: 28247459 DOI: 10.1111/gcb.13647] [Citation(s) in RCA: 163] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 01/19/2017] [Accepted: 01/23/2017] [Indexed: 05/18/2023]
Abstract
Many ecosystems around the world are rapidly deteriorating due to both local and global pressures, and perhaps none so precipitously as coral reefs. Management of coral reefs through maintenance (e.g., marine-protected areas, catchment management to improve water quality), restoration, as well as global and national governmental agreements to reduce greenhouse gas emissions (e.g., the 2015 Paris Agreement) is critical for the persistence of coral reefs. Despite these initiatives, the health and abundance of corals reefs are rapidly declining and other solutions will soon be required. We have recently discussed options for using assisted evolution (i.e., selective breeding, assisted gene flow, conditioning or epigenetic programming, and the manipulation of the coral microbiome) as a means to enhance environmental stress tolerance of corals and the success of coral reef restoration efforts. The 2014-2016 global coral bleaching event has sharpened the focus on such interventionist approaches. We highlight the necessity for consideration of alternative (e.g., hybrid) ecosystem states, discuss traits of resilient corals and coral reef ecosystems, and propose a decision tree for incorporating assisted evolution into restoration initiatives to enhance climate resilience of coral reefs.
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Affiliation(s)
- Madeleine J H van Oppen
- Australian Institute of Marine Science, PMB No. 3, Townsville MC, QLD, 4810, Australia
- School of BioSciences, University of Melbourne, Parkville, VIC, 3010, Australia
| | - Ruth D Gates
- Hawaii Institute of Marine Biology, Kaneohe, HI, 96744, USA
| | - Linda L Blackall
- School of BioSciences, University of Melbourne, Parkville, VIC, 3010, Australia
| | - Neal Cantin
- Australian Institute of Marine Science, PMB No. 3, Townsville MC, QLD, 4810, Australia
| | - Leela J Chakravarti
- Australian Institute of Marine Science, PMB No. 3, Townsville MC, QLD, 4810, Australia
- AIMS@JCU, James Cook University, Townsville, QLD, 4811, Australia
- College of Marine and Environmental Sciences, James Cook University, Townsville, QLD, 4811, Australia
| | - Wing Y Chan
- Australian Institute of Marine Science, PMB No. 3, Townsville MC, QLD, 4810, Australia
- School of BioSciences, University of Melbourne, Parkville, VIC, 3010, Australia
| | - Craig Cormick
- ThinkOutsideThe, 12 Giffen Close, Holt, ACT, 2615, Australia
| | - Angela Crean
- School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW, 2006, Australia
| | - Katarina Damjanovic
- Australian Institute of Marine Science, PMB No. 3, Townsville MC, QLD, 4810, Australia
- School of BioSciences, University of Melbourne, Parkville, VIC, 3010, Australia
| | - Hannah Epstein
- Australian Institute of Marine Science, PMB No. 3, Townsville MC, QLD, 4810, Australia
- AIMS@JCU, James Cook University, Townsville, QLD, 4811, Australia
- College of Marine and Environmental Sciences, James Cook University, Townsville, QLD, 4811, Australia
- Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD, 4811, Australia
| | - Peter L Harrison
- Marine Ecology Research Centre, School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW, Australia
| | - Thomas A Jones
- USDA-Agricultural Research Service, Forage and Range Research Laboratory, Logan, UT, 84322-6300, USA
| | - Margaret Miller
- National Oceanic and Atmospheric Administration-National Marine Fisheries Service, Miami, FL, USA
| | - Rachel J Pears
- Great Barrier Reef Marine Park Authority, PO Box 1379, Townsville, QLD, 4810, Australia
| | - Lesa M Peplow
- Australian Institute of Marine Science, PMB No. 3, Townsville MC, QLD, 4810, Australia
| | - David A Raftos
- Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2109, Australia
| | - Britta Schaffelke
- Australian Institute of Marine Science, PMB No. 3, Townsville MC, QLD, 4810, Australia
| | - Kristen Stewart
- SUNY College of Environmental Science and Forestry, Syracuse, NY, 13210-2788, USA
| | - Gergely Torda
- Australian Institute of Marine Science, PMB No. 3, Townsville MC, QLD, 4810, Australia
- Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD, 4811, Australia
| | - David Wachenfeld
- Great Barrier Reef Marine Park Authority, PO Box 1379, Townsville, QLD, 4810, Australia
| | - Andrew R Weeks
- School of BioSciences, University of Melbourne, Parkville, VIC, 3010, Australia
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9
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Abstract
Knowledge of the onset duration of the Paleocene-Eocene Thermal Maximum-the largest known greenhouse-gas-driven global warming event of the Cenozoic-is central to drawing inferences for future climate change. Single-foraminifera measurements of the associated carbon isotope excursion from Maud Rise (South Atlantic Ocean) are controversial, as they seem to indicate geologically instantaneous carbon release and anomalously long ocean mixing. Here, we fundamentally reinterpret this record and extract the likely PETM onset duration. First, we employ an Earth system model to illustrate how the response of ocean circulation to warming does not support the interpretation of instantaneous carbon release. Instead, we use a novel sediment-mixing model to show how changes in the relative population sizes of calcareous plankton, combined with sediment mixing, can explain the observations. Furthermore, for any plausible PETM onset duration and sampling methodology, we place a probability on not sampling an intermediate, syn-excursion isotopic value. Assuming mixed-layer carbonate production continued at Maud Rise, we deduce the PETM onset was likely <5 kyr.Single-foraminifera measurements of the PETM carbon isotope excursion from Maud Rise have been interpreted as indicating geologically instantaneous carbon release. Here, the authors explain these records using an Earth system model and a sediment-mixing model and extract the likely PETM onset duration.
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10
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Schaller MF, Fung MK, Wright JD, Katz ME, Kent DV. Impact ejecta at the Paleocene-Eocene boundary. Science 2017; 354:225-229. [PMID: 27738171 DOI: 10.1126/science.aaf5466] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 09/16/2016] [Indexed: 11/02/2022]
Abstract
Extraterrestrial impacts have left a substantial imprint on the climate and evolutionary history of Earth. A rapid carbon cycle perturbation and global warming event about 56 million years ago at the Paleocene-Eocene (P-E) boundary (the Paleocene-Eocene Thermal Maximum) was accompanied by rapid expansions of mammals and terrestrial plants and extinctions of deep-sea benthic organisms. Here, we report the discovery of silicate glass spherules in a discrete stratigraphic layer from three marine P-E boundary sections on the Atlantic margin. Distinct characteristics identify the spherules as microtektites and microkrystites, indicating that an extraterrestrial impact occurred during the carbon isotope excursion at the P-E boundary.
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Affiliation(s)
- Morgan F Schaller
- Earth and Environmental Sciences, Rensselaer Polytechnic Institute (RPI), Troy, NY 12180, USA.
| | - Megan K Fung
- Earth and Environmental Sciences, Rensselaer Polytechnic Institute (RPI), Troy, NY 12180, USA
| | - James D Wright
- Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA
| | - Miriam E Katz
- Earth and Environmental Sciences, Rensselaer Polytechnic Institute (RPI), Troy, NY 12180, USA
| | - Dennis V Kent
- Earth and Planetary Sciences, Rutgers University, Piscataway, NJ 08854, USA. Lamont-Doherty Earth Observatory (LDEO), Columbia University, Palisades, NY 10964, USA
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11
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Glikson A. Cenozoic mean greenhouse gases and temperature changes with reference to the Anthropocene. GLOBAL CHANGE BIOLOGY 2016; 22:3843-3858. [PMID: 27151305 DOI: 10.1111/gcb.13342] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 04/30/2016] [Indexed: 06/05/2023]
Abstract
Cenozoic greenhouse gases (GHG) variations and warming periods underscore the extreme rates of current climate change, with major implications for the adaptability and survivability of terrestrial and marine habitats. Current rise rate of greenhouse gases, reaching 3.3 ppm CO2 per year during March 2015-2016, is the fastest recorded since the Paleocene-Eocene Thermal Event (PETM) when carbon release to the atmosphere was about an order of magnitude less than at present. The ice core evidence of concentration of (GHG) and temperatures in the atmosphere/ocean/cryosphere system over the last 740 kyr suggests that the rate of rise in GHG over the last ~260 years, CO2 rates rising from 0.94 ppm yr-1 in 1959 (315.97 ppm) to 1.62 ppm yr-1 in 2000 (369.52 ppm) to 3.05 ppm yr-1 in 2015 (400.83 ppm), constitutes a unique spike in the history of the atmosphere. The reliance of pre-740 kyr paleoclimate estimates on multiple proxies, including benthic and plankton fossils, fossil plants, residual organic matter, major and trace elements in fossils, sediments and soils, place limits on the resolution of pre-upper Pleistocene paleoclimate estimates, rendering it likely recorded mean Cenozoic paleoclimate trends may conceal abrupt short-term climate fluctuations. However, as exemplified by the Paleocene-Eocene thermal maximum (PETM) and earlier GHG and temperature spikes associated with major volcanic and asteroid impact events, the long-term residence time of CO2 in the atmosphere extends the signatures of abrupt warming events to within detection limits of multiple paleoproxies. The mean post-1750 temperature rise rate (approximately ~0.0034 °C per yr, or ~0.008 °C per yr where temperature is not masked by sulfur aerosols) exceeds those of the PETM (approximately ~0.0008-0.0015 °C per yr) by an order of magnitude and mean glacial termination warming rates (last glacial termination [LGT] ~ 0.00039; Eemian ~0.0004 °C per yr) by near to an order of magnitude. Consistent with previous interglacial peaks an increasing likelihood of collapse of the Atlantic Meridional Ocean Circulation is threatening a severe stadial event.
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Affiliation(s)
- Andrew Glikson
- Australian National University, Canberra, ACT, 2601, Australia
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Chavas JP, Grainger C, Hudson N. How should economists model climate? Tipping points and nonlinear dynamics of carbon dioxide concentrations. JOURNAL OF ECONOMIC BEHAVIOR & ORGANIZATION 2016; 132:56-65. [PMID: 30078923 PMCID: PMC6071419 DOI: 10.1016/j.jebo.2016.01.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Economists modeling climate policy face an array of choices when modeling climate change, including the role of uncertainty/ambiguity, irreversibility, and tipping points. After filtering out estimated cycles due to orbital climate forcing, we use a threshold quantile autoregressive model to characterize anomalies in atmospheric CO2 concentrations. We then test for local instability and tipping points, and we characterize the stationary distribution of anomalies. We find evidence of nonlinear dynamics, tipping points and a non-normal stationary distribution.
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13
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Bell JB, Aquilina A, Woulds C, Glover AG, Little CTS, Reid W, Hepburn LE, Newton J, Mills RA. Geochemistry, faunal composition and trophic structure in reducing sediments on the southwest South Georgia margin. ROYAL SOCIETY OPEN SCIENCE 2016; 3:160284. [PMID: 27703692 PMCID: PMC5043311 DOI: 10.1098/rsos.160284] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 08/25/2016] [Indexed: 05/05/2023]
Abstract
Despite a number of studies in areas of focused methane seepage, the extent of transitional sediments of more diffuse methane seepage, and their influence upon biological communities is poorly understood. We investigated an area of reducing sediments with elevated levels of methane on the South Georgia margin around 250 m depth and report data from a series of geochemical and biological analyses. Here, the geochemical signatures were consistent with weak methane seepage and the role of sub-surface methane consumption was clearly very important, preventing gas emissions into bottom waters. As a result, the contribution of methane-derived carbon to the microbial and metazoan food webs was very limited, although sulfur isotopic signatures indicated a wider range of dietary contributions than was apparent from carbon isotope ratios. Macrofaunal assemblages had high dominance and were indicative of reducing sediments, with many taxa common to other similar environments and no seep-endemic fauna, indicating transitional assemblages. Also similar to other cold seep areas, there were samples of authigenic carbonate, but rather than occurring as pavements or sedimentary concretions, these carbonates were restricted to patches on the shells of Axinulus antarcticus (Bivalvia, Thyasiridae), which is suggestive of microbe-metazoan interactions.
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Affiliation(s)
- James B. Bell
- School of Geography and Water@Leeds, University of Leeds, Leeds LS2 9JT, UK
- Life Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK
- Author for correspondence: James B. Bell e-mail:
| | - Alfred Aquilina
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton SO14 3ZH, UK
| | - Clare Woulds
- School of Geography and Water@Leeds, University of Leeds, Leeds LS2 9JT, UK
| | - Adrian G. Glover
- Life Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK
| | | | | | - Laura E. Hepburn
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton SO14 3ZH, UK
| | - Jason Newton
- NERC Life Sciences Mass Spectrometry Facility, SUERC, East Kilbride G75 0QF, UK
| | - Rachel A. Mills
- Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton SO14 3ZH, UK
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14
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Quantified abundance of magnetofossils at the Paleocene-Eocene boundary from synchrotron-based transmission X-ray microscopy. Proc Natl Acad Sci U S A 2015; 112:12598-603. [PMID: 26420869 DOI: 10.1073/pnas.1517475112] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Paleocene-Eocene boundary (∼55.8 million years ago) is marked by an abrupt negative carbon isotope excursion (CIE) that coincides with an oxygen isotope decrease interpreted as the Paleocene-Eocene thermal maximum. Biogenic magnetite (Fe3O4) in the form of giant (micron-sized) spearhead-like and spindle-like magnetofossils, as well as nano-sized magnetotactic bacteria magnetosome chains, have been reported in clay-rich sediments in the New Jersey Atlantic Coastal Plain and were thought to account for the distinctive single-domain magnetic properties of these sediments. Uncalibrated strong field magnet extraction techniques have been typically used to provide material for scanning and transmission electron microscopic imaging of these magnetic particles, whose concentration in the natural sediment is thus difficult to quantify. In this study, we use a recently developed ultrahigh-resolution, synchrotron-based, full-field transmission X-ray microscope to study the iron-rich minerals within the clay sediment in their bulk state. We are able to estimate the total magnetization concentration of the giant biogenic magnetofossils to be only ∼10% of whole sediment. Along with previous rock magnetic studies on the CIE clay, we suggest that most of the magnetite in the clay occurs as isolated, near-equidimensional nanoparticles, a suggestion that points to a nonbiogenic origin, such as comet impact plume condensates in what may be very rapidly deposited CIE clays.
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Reply to Pearson and Nicholas, Stassen et al., and Zeebe et al.: Teasing out the missing piece of the PETM puzzle. Proc Natl Acad Sci U S A 2014; 111:E1068-71. [PMID: 24829945 DOI: 10.1073/pnas.1321876111] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Onset of carbon isotope excursion at the Paleocene-Eocene thermal maximum took millennia, not 13 years. Proc Natl Acad Sci U S A 2014; 111:E1062-3. [PMID: 24572570 DOI: 10.1073/pnas.1321177111] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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Layering in the Paleocene/Eocene boundary of the Millville core is drilling disturbance. Proc Natl Acad Sci U S A 2014; 111:E1064-5. [PMID: 24572569 DOI: 10.1073/pnas.1322077111] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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