News

Multiple episodes of extensive marine anoxia linked to global warming and continental weathering following the latest Permian mass extinction

Abstract.

"Explaining the ~5-million-year delay in marine biotic recovery following the latest Permian mass extinction, the largest biotic crisis of the Phanerozoic, is a fundamental challenge for both geological and biological sciences. Ocean redox perturbations may have played a critical role in this delayed recovery. However, the lack of quantitative constraints on the details of Early Triassic oceanic anoxia (for example, time, duration, and extent) leaves the links between oceanic conditions and the delayed biotic recovery ambiguous. [...]"

Source: Science Advances
Authors: Feifei Zhan et al.
DOI:10.1126/sciadv.1602921

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Ocean euxinia and climate change "double whammy" drove the Late Ordovician mass extinction

Abstract.

"The Late Ordovician mass extinction (LOME, ca. 445 Ma) was the first of the "Big Five" Phanerozoic extinction events and comprised two extinction pulses. Proposed kill mechanisms include glacially induced global cooling and the expansion of water-column anoxia and/or euxinia (sulfidic conditions), but no general consensus has been reached with regard to the precise role of these mechanisms. [...]"

Source: Geology
Authors: Caineng Zou et al.
DOI: 10.1130/G40121.1

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Oxic Fe(III) reduction could have generated Fe(II) in the photic zone of Precambrian seawater

Abstract.

"Many marine Precambrian iron formations (IF) record deep anoxic seawater enriched in Fe(II) (i.e. ferruginous) overlain by mildly oxygenated surface water. This is reflected by iron-rich sediments forming in deep basins, and relatively iron-poor sediments forming in shallow, sunlit waters. Such an iron gradient is often interpreted as a redox interface where dissolved Fe(II) was oxidized and precipitated as Fe(III)-bearing minerals. As such, sedimentary iron enrichments are proxy to the progressive oxidation of the oceans through geological time. [...]"

Source: Scientific Reportsvolume
Authors: Elizabeth D. Swanner
DOI: 10.1038/s41598-018-22694-y

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The influence of the ocean circulation state on ocean carbon storage and CO2 drawdown potential in an Earth system model

Abstract.

"During the four most recent glacial cycles, atmospheric CO2 during glacial maxima has been lowered by about 90–100 ppm with respect to interglacials. There is widespread consensus that most of this carbon was partitioned in the ocean. It is, however, still debated which processes were dominant in achieving this increased carbon storage. In this paper, we use an Earth system model of intermediate complexity to explore the sensitivity of ocean carbon storage to ocean circulation state. We carry out a set of simulations in which we run the model to pre-industrial equilibrium, but in which we achieve different states of ocean circulation by changing forcing parameters such as wind stress, ocean diffusivity and atmospheric heat diffusivity. [...]"

Source: Biogeosciences
Authors: Malin Ödalen et al.
DOI: 10.5194/bg-15-1367-2018

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Nitrogen fixation sustained productivity in the wake of the Palaeoproterozoic Great Oxygenation Event

Abstract.

"The marine nitrogen cycle is dominated by redox-controlled biogeochemical processes and, therefore, is likely to have been revolutionised in response to Earth-surface oxygenation. The details, timing, and trajectory of nitrogen cycle evolution, however, remain elusive. Here we couple nitrogen and carbon isotope records from multiple drillcores through the Rooihoogte–Timeball Hill Formations from across the Carletonville area of the Kaapvaal Craton where the Great Oxygenation Event (GOE) and its aftermath are recorded. [...]"

Source: Nature Communications
Authors: Genming Luo
DOI: 10.1038/s41467-018-03361-2

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Uranium isotope evidence for two episodes of deoxygenation during Oceanic Anoxic Event 2

Abstract.

"Oceanic Anoxic Event 2 (OAE 2), occurring ∼94 million years ago, was one of the most extreme carbon cycle and climatic perturbations of the Phanerozoic Eon. It was typified by a rapid rise in atmospheric CO2, global warming, and marine anoxia, leading to the widespread devastation of marine ecosystems. However, the precise timing and extent to which oceanic anoxic conditions expanded during OAE 2 remains unresolved. [...]"

Source: PNAS
Authors: Matthew O. Clarkson et al.
DOI: 10.1073/pnas.1715278115

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Oxygen loss could be a huge issue for oceans

"A major study into an ancient climate change event that affected a significant percentage of Earth’s oceans has brought into sharp focus a lesser-known villain in global warming: oxygen depletion. 

The study, just published in the prestigious Proceedings of the National Academy of Sciences (PNAS), examined a past period of global warming around 94 million years ago, when oceans became de-oxygenated.

This famous period in Earth’s geological history, known as an Oceanic Anoxic Event (OAE), was more severe and on much longer timescales than the current changes. But it has given the scientists studying this period an extreme case-study to help understand how the oceans are effected by high atmospheric CO2 emissions. [...]"

Source: University of Exeter News

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Oceanic crustal carbon cycle drives 26-million-year atmospheric carbon dioxide periodicities

Abstract.

"Atmospheric carbon dioxide (CO2) data for the last 420 million years (My) show long-term fluctuations related to supercontinent cycles as well as shorter cycles at 26 to 32 My whose origin is unknown. Periodicities of 26 to 30 My occur in diverse geological phenomena including mass extinctions, flood basalt volcanism, ocean anoxic events, deposition of massive evaporites, sequence boundaries, and orogenic events and have previously been linked to an extraterrestrial mechanism. [...]

Source: Science Advances
Authors: R. Dietmar Müller and Adriana Dutkiewicz
DOI: 10.1126/sciadv.aaq0500

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Tropical Atlantic climate and ecosystem regime shifts during the Paleocene–Eocene Thermal Maximum

Abstract.

"The Paleocene–Eocene Thermal Maximum (PETM, 56 Ma) was a phase of rapid global warming associated with massive carbon input into the ocean–atmosphere system from a C-depleted reservoir. Many midlatitude and high-latitude sections have been studied and document changes in salinity, hydrology and sedimentation, deoxygenation, biotic overturning, and migrations, but detailed records from tropical regions are lacking. [...]"

Source: Climate of the Past
Authors: Joost Frieling et al.
DOI: 10.5194/cp-14-39-2018

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A record of deep-ocean dissolved O2 from the oxidation state of iron in submarine basalts

Abstract.

"The oxygenation of the deep ocean in the geological past has been associated with a rise in the partial pressure of atmospheric molecular oxygen (O2) to near-present levels and the emergence of modern marine biogeochemical cycles. It has also been linked to the origination and diversification of early animals. [...]"

Source: Nature
Authors: Daniel A. Stolper
DOI: 10.1038/nature25009

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