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Summary:

Researchers are looking to the geologic past to make future projections about climate change. Their research focuses on the ancient Tethys Ocean (site of the present-day Mediterranean Sea) and provides a benchmark for present and future climate and ocean models.

Source: Science Daily

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Perturbation to the nitrogen cycle during rapid Early Eocene global warming

Abstract.

"The degree to which ocean deoxygenation will alter the function of marine communities remains unclear but may be best constrained by detailed study of intervals of rapid warming in the geologic past. The Paleocene–Eocene Thermal Maximum (PETM) was an interval of rapid warming that was the result of increasing contents of greenhouse gases in the atmosphere that had wide ranging effects on ecosystems globally. Here, we present stable nitrogen isotope data from the Eastern Peri-Tethys Ocean that record a significant transition in the nitrogen cycle.  [...]"

Source: Nature Communications
Authors: Christopher K. Junium, Alexander J. Dickson & Benjamin T. Uveges 
DOI: 10.1038/s41467-018-05486-w

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Middle Eocene greenhouse warming facilitated by diminished weathering feedback

Abstract.

"The Middle Eocene Climatic Optimum (MECO) represents a ~500-kyr period of global warming ~40 million years ago and is associated with a rise in atmospheric CO2 concentrations, but the cause of this CO2 rise remains enigmatic. Here we show, based on osmium isotope ratios (187Os/188Os) of marine sediments and published records of the carbonate compensation depth (CCD), that the continental silicate weathering response to the inferred CO2 rise and warming was strongly diminished during the MECO—in contrast to expectations from the silicate weathering thermostat hypothesis. [...]"

Source: Nature Communications
Authors: Robin van der Ploeg et al.
DOI: 10.1038/s41467-018-05104-9

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Early Palaeozoic ocean anoxia and global warming driven by the evolution of shallow burrowing

Abstract.

"The evolution of burrowing animals forms a defining event in the history of the Earth. It has been hypothesised that the expansion of seafloor burrowing during the Palaeozoic altered the biogeochemistry of the oceans and atmosphere. However, whilst potential impacts of bioturbation on the individual phosphorus, oxygen and sulphur cycles have been considered, combined effects have not been investigated, leading to major uncertainty over the timing and magnitude of the Earth system response to the evolution of bioturbation. [...]"

Source: Nature Communications
Authors: Sebastiaan van de Velde et al.
DOI: 10.1038/s41467-018-04973-4

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Coupling of ocean redox and animal evolution during the Ediacaran-Cambrian transition

Abstract.

"The late Ediacaran to early Cambrian interval witnessed extraordinary radiations of metazoan life. The role of the physical environment in this biological revolution, such as changes to oxygen levels and nutrient availability, has been the focus of longstanding debate. Seemingly contradictory data from geochemical redox proxies help to fuel this controversy. As an essential nutrient, nitrogen can help to resolve this impasse by establishing linkages between nutrient supply, ocean redox, and biological changes. [...]"

Source: Nature Communications
Authors: Dan Wang et al.
DOI: 10.1038/s41467-018-04980-5

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Oxygen minimum zones in the early Cambrian ocean

Abstract.

"The relationship between the evolution of early animal communities and oceanic oxygen levels remains unclear. In particular, uncertainty persists in reconstructions of redox conditions during the pivotal early Cambrian (541-510 million years ago, Ma), where conflicting datasets from deeper marine settings suggest either ocean anoxia or fully oxygenated conditions. By coupling geochemical palaeoredox proxies with a record of organic-walled fossils from exceptionally well-defined successions of the early Cambrian Baltic Basin, we provide evidence for the early establishment of modern-type oxygen minimum zones (OMZs). [...]"

Source: Geochemical Perspectives Letters 
Authors: R. Guilbaud et al.
DOI: 10.7185/geochemlet.1806

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Early Palaeozoic ocean anoxia and global warming driven by the evolution of shallow burrowing

Abstract.

"The evolution of burrowing animals forms a defining event in the history of the Earth. It has been hypothesised that the expansion of seafloor burrowing during the Palaeozoic altered the biogeochemistry of the oceans and atmosphere. However, whilst potential impacts of bioturbation on the individual phosphorus, oxygen and sulphur cycles have been considered, combined effects have not been investigated, leading to major uncertainty over the timing and magnitude of the Earth system response to the evolution of bioturbation. [...]"

Source: Nature Communications
Authors: Sebastiaan van de Velde et al.
DOI: 10.1038/s41467-018-04973-4

Read the full article here.


Extensive marine anoxia during the terminal Ediacaran Period

Abstract.

"The terminal Ediacaran Period witnessed the decline of the Ediacara biota (which may have included many stem-group animals). To test whether oceanic anoxia might have played a role in this evolutionary event, we measured U isotope compositions (δ238U) in sedimentary carbonates from the Dengying Formation of South China to obtain new constraints on the extent of global redox change during the terminal Ediacaran. [...]"

Source: Science Advances
Authors: Feifei Zhang et al.
DOI: 10.1126/sciadv.aan8983

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Marine redox fluctuation as a potential trigger for the Cambrian explosion

Abstract.

The diversification of metazoans during the latest Neoproterozoic and early Cambrian has been attributed to, among other factors, a progressive rise in surface oxygen levels. However, recent results have also questioned the idea of a prominent rise in atmospheric oxygen levels or a major or unidirectional shift in the marine redox landscape across this interval. Here, we present new carbonate-associated uranium isotope data from upper Ediacaran to lower Cambrian marine carbonate successions. [...]"

Source: Geology
Authors: Guang-Yi Wei et al.
DOI: 10.1130/G40150.1

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Climate and marine biogeochemistry during the Holocene from transient model simulations

Abstract.

"Climate and marine biogeochemistry changes over the Holocene are investigated based on transient global climate and biogeochemistry model simulations over the last 9500 years. The simulations are forced by accelerated and non-accelerated orbital parameters, respectively, and atmospheric pCO2, CH4, and N2O. The analysis focusses on key climatic parameters of relevance to the marine biogeochemistry, and on the physical and biogeochemical processes that drive atmosphere–ocean carbon fluxes and changes in the oxygen minimum zones (OMZs). [...]"

Source: Biogeosciences
Authors: Joachim Segschneider, Birgit Schneider, and Vyacheslav Khon
DOI: 10.5194/bg-15-3243-2018

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