News

Unravelling the sources of carbon emissions at the onset of Oceanic Anoxic Event (OAE) 1a

Abstract.

"The early Aptian Oceanic Anoxic Event (OAE) 1a represents a major perturbation of the Earth's climate system and in particular the carbon cycle, as evidenced by widespread preservation of organic matter in marine settings and a characteristic negative carbon isotopic excursion (CIE) at its onset, followed by a broad positive CIE. The contemporaneous emplacement of a large igneous province (LIP) is invoked as a trigger for OAE 1a (and OAEs in general), but this link and the ultimate source of the carbon perturbation at the onset of OAEs is still debated. [...]"

Source: 
Authors: Markus Adloff et al.
DOI: 10.1016/j.epsl.2019.115947

Read the full article here.


Cretaceous Oceanic Anoxic Events prolonged by phosphorus cycle feedbacks

Abstract.

"Oceanic Anoxic Events (OAEs) document major perturbations of the global carbon cycle with repercussions on the Earth’s climate and ocean circulation that are relevant to understand future climate trends. Here, we compare sedimentation patterns, nutrient cycling, organic carbon accumulation and carbon isotope variability across Cretaceous Oceanic Anoxic Events OAE1a and OAE2 in two drill cores with unusually high sedimentation rates from the Vocontian Basin (southern France) and Tarfaya Basin (southern Morocco). [...]"

Source: Climate of the Past (Preprint)
Authors: Sebastian Beil et al.
DOI: 10.5194/cp-2019-118

Read the full article here.


Atmosphere–ocean oxygen and productivity dynamics during early animal radiations

Abstract.

"The proliferation of large, motile animals 540 to 520 Ma has been linked to both rising and declining O2 levels on Earth. To explore this conundrum, we reconstruct the global extent of seafloor oxygenation at approximately submillion-year resolution based on uranium isotope compositions of 187 marine carbonates samples from China, Siberia, and Morocco, and simulate O2 levels in the atmosphere and surface oceans using a mass balance model constrained by carbon, sulfur, and strontium isotopes in the same sedimentary successions. [...]"

Source: PNAS
Authors: Tais W. Dahl et al.
DOI: 10.1073/pnas.1901178116

Read the full article here.


High-resolution records of Oceanic Anoxic Event 2:

Insights into the timing, duration and extent of environmental perturbations from the palaeo-South Pacific Ocean

Abstract.

"Oceanic Anoxic Event 2 (OAE 2), which took place around the Cenomanian–Turonian boundary (∼94 Ma), is associated with extreme perturbations to the global carbon cycle, affected ocean basins worldwide and was associated with significant biological turnover. Although this event has been well studied in the northern hemisphere, the evolution and character of OAE 2, particularly in terms of the vertical and lateral extent of anoxia, is poorly constrained in the palaeo-Pacific Ocean. [...]"

Source: Earth and Planetary Science Letters
Authors: S. K. Gangl et al.
DOI: 10.1016/j.epsl.2019.04.028

Read the full article here.


The far-future ocean: Warm yet oxygen-rich

"The oceans are losing oxygen. Numerous studies based on direct measurements in recent years have shown this. Since water can dissolve less gas as temperatures rise, these results were not surprising. In addition to global warming, factors such as eutrophication of the coastal seas also contribute to the ongoing deoxygenation. [...]"

Source: Phys.org

Read the full article here.


Loss of fixed nitrogen causes net oxygen gain in a warmer future ocean

Abstract.

"Oceanic anoxic events have been associated with warm climates in Earth history, and there are concerns that current ocean deoxygenation may eventually lead to anoxia. Here we show results of a multi-millennial global-warming simulation that reveal, after a transitory deoxygenation, a marine oxygen inventory 6% higher than preindustrial despite an average 3 °C ocean warming. [...]"

Source: Nature Communications
Authors: Andreas Oschlies et al.
DOI: 10.1038/s41467-019-10813-w

Read the full article here.


Biomarker evidence for the occurrence of anaerobic ammonium oxidation in the eastern Mediterranean Sea during Quaternary and Pliocene sapropel formati

Abstract.

"The eastern Mediterranean Sea sedimentary record is characterised by intervals of organic rich sediment (sapropels), indicating periods of severe anoxia triggered by astronomical forcing. It has been hypothesized that nitrogen fixation was crucial in injecting the Mediterranean Sea with bioavailable nitrogen (N) during sapropel events. However, the evolution of the N biogeochemical cycle of sapropels is poorly understood. For example, the role of the complementary removal reaction, anaerobic ammonium oxidation (anammox), has not been investigated because the traditional lipid biomarkers for anammox, ladderane fatty acids, are not stable over long periods in the sedimentary record. [...]

Source: Biogeosciences
Authors: Darci Rush et al.
DOI: 10.5194/bg-2019-27

Read the full article here.

 


Southern Hemisphere sea-surface temperatures during the Cenomanian–Turonian: Implications for the termination of Oceanic Anoxic Event 2

Abstract.

"Mesozoic oceanic anoxic events (OAEs) were major perturbations of the Earth system, associated with high CO2 concentrations in the oceans and atmosphere, high temperatures, and widespread organic-carbon burial. Models for explaining OAEs and other similar phenomena in Earth history make specific predictions about the role and pattern of temperature change, which can be tested through comparison with the geological record. Oceanic Anoxic Event 2 (OAE 2) occurred ~94 m.y. ago and is commonly considered as the type example of an OAE. [...]"

Source: Geology 
Authors: Stuart A. Robinson et al.
DOI: 10.1130/G45842.1

Read the full article here.


Organic carbon burial during OAE2 driven by changes in the locus of organic matter sulfurization

Abstract.

"Ocean Anoxic Event 2 (OAE2) was a period of dramatic disruption to the global carbon cycle when massive amounts of organic matter (OM) were buried in marine sediments via complex and controversial mechanisms. Here we investigate the role of OM sulfurization, which makes OM less available for microbial respiration, in driving variable OM preservation in OAE2 sedimentary strata from Pont d’Issole (France). We find correlations between the concentration, S:C ratio, S-isotope composition, and sulfur speciation of OM suggesting that sulfurization facilitated changes in carbon burial at this site as the chemocline moved in and out of the sediments during deposition. [...]"

Source: Nature Communications
Authors: Morgan Reed Raven et al.
DOI: 10.1038/s41467-018-05943-6

Read the full article here.


Transient cooling episodes during Cretaceous Oceanic Anoxic Events with special reference to OAE 1a (Early Aptian)

Abstract.

"The two major oceanic anoxic events of the Cretaceous, those of the Early Aptian (OAE 1a) and the Cenomanian–Turonian boundary (OAE 2), registered some of the highest temperatures reconstructed for the Cretaceous Period, and are thought to be related to the input of volcanically derived carbon dioxide from one or more Large Igneous Provinces. Widely distributed deposition of marine organic matter, the hallmark of OAEs, and intensified silicate weathering in response to a globally accelerated hydrological cycle and/or reaction of seawater with freshly extruded basalt, are both potential mechanisms whereby the content of atmospheric carbon dioxide could have been drawn down to promote cooling, on the assumption that this potential effect was not offset by increased addition of this volcanically derived greenhouse gas. [...]"

Source: Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences
Author: Hugh C. Jenkyns
DOI: 10.1098/rsta.2017.0073

Read the full article here.


Showing 1 - 10 of 20 results.
Items per Page 10
of 2