News

Spatial pattern of marine oxygenation set by tectonic and ecological drivers over the Phanerozoic

Abstract.

"Marine redox conditions (that is, oxygen levels) impact a wide array of biogeochemical cycles, but the main controls of marine redox since the start of the Phanerozoic about 538 million years ago are not well established. Here we combine supervised machine learning with shale-hosted trace metal concentrations to reconstruct a near-continuous record of redox conditions in major marine depositional settings. We find synchronously opposite redox changes in upper ocean versus deep shelf and (semi-)restricted basin settings ('redox anticouples', nomen novum) in several multi-million-year intervals, which can be used to track the positions of oxygen-minimum zones and the primary locations of organic burial through time. [...]".

 

Source: Nature
Authors: Xiangli Wang et al. 
DOI: https://doi.org/10.1038/s41561-023-01296-y

Read the full article here.


Dynamical Response of the Arabian Sea Oxygen Minimum Zone to the Extreme Indian Ocean Dipole Events in 2016 and 2019

Abstract.

"The Indian Ocean Dipole (IOD) plays a crucial role in shaping local and global environments, yet its effects on interannual variability of the Arabian Sea oxygen minimum zone (ASOMZ) remains poorly understood. Here, we used a coupled physical-biogeochemical model to investigate the dynamical response of the ASOMZ to extreme negative (2016) and positive (2019) IOD events. Our findings revealed that the suboxic area of the ASOMZ reduced (expanded) by ∼27% (∼28%) after the negative (positive) IOD event. [...]".

 

Source: Wiley Online Library
Authors: Zhiwei Zhang et al.
DOI: https://doi.org/10.1029/2023GL104226

Read the full article here.


Effect of an Open Central American Seaway on Ocean Circulation and the Oxygen Minimum Zone in the Tropical Pacific From Model Simulations

Abstract.

"The tectonic closure of the Central American Seaway (CAS) during the mid-Miocene to mid-Pliocene (∼16–3 Ma BP) is thought of as a key interval for the onset of the present-day tropical Pacific oxygen minimum zone (OMZ). In this study we investigate the impact of an open CAS on the ocean circulation and the OMZ in the tropical Pacific. We perform a series of sensitivity experiments with the Kiel Climate Model, where we vary the CAS sill depth from shallow to deep. [...]".

 

Source: Wiley Online Library
Authors: Vyacheslav Khon et al. 
DOI: https://doi.org/10.1029/2023GL103728

Read the full article here.


Future change of summer hypoxia in coastal California Current

Abstract.

"The occurrences of summer hypoxia in coastal California Current can significantly affect the benthic and pelagic habitat and lead to complex ecosystem changes. Model-simulated hypoxia in this region is strongly spatially heterogeneous, and its future changes show uncertainties depending on the model used. Here, we used an ensemble of the new generation Earth system models to examine the present-day and future changes of summer hypoxia in this region. We applied model-specific thresholds combined with empirical bias adjustments of the dissolved oxygen variance to identify hypoxia. [...]".

 

Source: Frontiers in Marine Science 
Authors: Hui Shi et al.
DOI: https://doi.org/10.3389/fmars.2023.1205536

Read the full article here.


Decadal variability of oxygen uptake, export, and storage in the Labrador Sea from observations and CMIP6 models

Abstract.

"The uptake of dissolved oxygen from the atmosphere via air-sea gas exchange and its physical transport away from the region of uptake are crucial for supplying oxygen to the deep ocean. This process takes place in a few key regions that feature intense oxygen uptake, deep water formation, and physical oxygen export. In this study we analyze one such region, the Labrador Sea, utilizing the World Ocean Database (WOD) to construct a 65–year oxygen content time series in the Labrador Sea Water (LSW) layer (0–2200 m). [...]".

 

Source: Frontiers in Marine Science 
Authors: Jannes Koelling et al.
DOI: https://doi.org/10.3389/fmars.2023.1202299

Read the full article here.


Carbonate uranium isotopes across Cretaceous OAE 2 in southern Mexico: New constraints on the global spread of marine anoxia and organic carbon burial

Abstract.

"Oceanic anoxic events (OAEs) represent discrete intervals of decreased marine oxygen concentrations often associated with volcanism, enhanced organic carbon burial coupled with positive δ13C excursions, and significant biotic turnover. Cretaceous OAE 2 (ca. 94 Mya) is especially notable for globally-distributed changes in calcareous invertebrate and plankton populations. While the presence of organic-rich facies is consistent with locally anoxic environments in many cases, determining the global extent of anoxia is more problematic. [...]".

 

Source: Science Direct
Authors: Joseph T. Kulenguski et al.
DOI: https://doi.org/10.1016/j.palaeo.2023.111756

Read the full article here.


Editorial: Oxygen decline in coastal waters: its cause, present situation and future projection

Abstract.

"The decline of oxygen levels in coastal waters has emerged as a significant and pressing concern, carrying extensive ecological and environmental ramifications. Coastal areas, the interface between land and sea, represent intricate and dynamic ecosystems that hold paramount importance for global biodiversity and sustain a multitude of human activities. Nevertheless, these coastal regions are confronted with mounting stressors originating from both human-induced factors such as nutrient pollution [...]".

 

Source: Frontiers in Marine Science
Authors: Weiwei Fu & Tsuneo Ono
DOI: https://doi.org/10.3389/fmars.2023.1316092

Read the full article here.


Oxygenation of the Baltoscandian shelf linked to Ordovician biodiversification

Abstract.

"Marine biodiversity increased markedly during the Ordovician Period (~487–443 million years ago). Some intervals within the Ordovician were associated with unusually rapid and prominent rises in taxonomic richness, the reasons for which remain debated. Links between increased oxygenation and biodiversification have been proposed, although supporting marine oxygen proxy data are limited. Here we present an expansive multi-site iodine-to-calcium (I/Ca) record from Lower–Middle Ordovician marine carbonates in Baltoscandia that provides a detailed account of the spatio-temporal development of oxygen conditions across this palaeoshelf. [...]".

 

Source: Nature
Authors: Anders Lindskog et al.
DOI: https://doi.org/10.1038/s41561-023-01287-z

Read the full article here.


Job Offer in ocean coupled physical-biogeochemical modelling

PhD or mobility postdoctoral position: "Predicting marine deoxygenation from earth observation data using machine learning."

"A 4-year PhD or a 2-year postdoctoral position is available at the Liège University (MAST group, Department of Astrophysics, Geophysics and Oceanography) to develop prediction tools of deoxygenation. The developed approach will combine earth observation (EO), ARGO and mechanistic model products with machine learning to predict coastal hypoxia and sub-surface oxycline variability. The position is offered in the frame of the “Multiple Threats on Ocean Health”(MiTHo) research project funded by the European Space Agency."

You can find more details in this document


Job Offer in ocean coupled physical-biogeochemical modelling

PhD or mobility postdoctoral position: "Projecting the Black Sea’s ecosystem and ecosystem services in a future climate. Trends, tipping points and resilience assessment."

"A 4-year PhD or 2-year postdoctoral position is available at the Liège University (MAST group, Department of Astrophysics, Geophysics and Oceanography) in collaboration with the Stockholm Resilience centre to perform and analyse regional climate model projections over the Black Sea.
The research project aims at performing an ensemble of model simulations of the physical and biogeochemical state of the Black Sea over different scenarios of atmospheric conditions and river discharges. The modelling system consists of a (one-way) coupled atmosphere-ocean model. The atmospheric model is the regional atmospheric model (MAR), the oceanographic model couples the Nucleus for European Modelling of the Ocean (NEMO) hydrodynamical model and the BiogeochemicAl Model for Hypoxic and Benthic Influenced areas (BAMHBI). The different components of the modelling system are run at the Liège University in the frame of European projects."

You can find more details in this document


Oxygenated deep waters fed early Atlantic overturning circulation upon Antarctic glaciation

Abstract.

"The Atlantic meridional overturning circulation (AMOC) exerts a major control on the global distribution of heat, dissolved oxygen and carbon in the ocean. Yet the timing and cause of the inception of this system and its evolution since the start of the Cenozoic Era 65 million years ago (Ma) remain highly uncertain. Here we present records of microbial source indicators based on glycerol dialkyl glycerol tetraether distributions from the Cenozoic Northwest Atlantic Ocean (~43‒18 Ma) and use them to infer changes in AMOC-driven deep-ocean oxygenation. [...]".

 

Source: Nature
Authors: Huanye Wang et al.
DOI: https://doi.org/10.1038/s41561-023-01292-2

Read the full article here.


Combined effects of ocean deoxygenation, acidification, and phosphorus limitation on green tide macroalga, Ulva prolifera

Abstract.

"Ocean deoxygenation, acidification, and decreased phosphorus availability are predicted to increase in coastal ecosystems under future climate change. However, little is known regarding the combined effects of such environmental variables on the green tide macroalga Ulva prolifera. Here, we provide quantitative and mechanistic understanding of the acclimation mechanisms of U. prolifera to ocean deoxygenation, acidification, and phosphorus limitation under both laboratory and semi-natural (mesocosms) conditions. [...]".

 

Source: Science Direct
Authors: Xintong Huang et al.
DOI: https://doi.org/10.1016/j.scitotenv.2023.164982

Read the full article here.


Hands-on Hypoxia: Engaging High School Educators in the science behind Marine Microbial Dynamics in Hypoxic Coastal Areas ...

Full title: "Hands-on Hypoxia: Engaging High School Educators in the science behind Marine Microbial Dynamics in Hypoxic Coastal Areas Through Field and Classroom Experiences"

Abstract.

"The University of Southern California’s (USC) Joint Educational Project’s STEM Education Programs hosted a three-day summer workshop focused on marine microbiology and coastal deoxygenation for high school educators. To increase ocean literacy in high school students from Title I schools, topical marine science research was translated into four lesson plans appropriate for classrooms that teach biology and environmental science. [...]".

 

Source: Current Journal
Authors: Kyla J. Kelly et al.
DOI: https://doi.org/10.5334/cjme.86

Read the full article here.

 


Expansion of Ocean Anoxia During Glacial Periods Recorded in the Cobalt Flux to Pelagic Sediments

Abstract.

"The expansion of oxygen deficient zones (ODZs) within the ocean's interior is anticipated to be a major consequence of anthropogenic climate change, but past changes in ODZs are poorly defined. Recent mapping efforts have revealed plumes of the redox-active metal cobalt within ODZs, driving a basin-scale correlation between high cobalt and low O2. Here, we investigate the cobalt flux to Equatorial Pacific sediments along the Line Islands Ridge as a novel record of basin-scale fluctuations in ODZ extent. [...]".

 

Source: Wiley Online Library
Authors: Nicholas J. Hawco & Rhea K. Foreman
DOI: https://doi.org/10.1029/2023GL105135

Read the full article here.


GOBAI-O2: temporally and spatially resolved fields of ocean interior dissolved oxygen over nearly 2 decades

Abstract.

"For about 2 decades, oceanographers have been installing oxygen sensors on Argo profiling floats to be deployed throughout the world ocean, with the stated objective of better constraining trends and variability in the ocean's inventory of oxygen. Until now, measurements from these Argo-float-mounted oxygen sensors have been mainly used for localized process studies on air–sea oxygen exchange, upper-ocean primary production, biological pump efficiency, and oxygen minimum zone dynamics. Here, we present a new four-dimensional gridded product of ocean interior oxygen, derived via machine learning algorithms trained on dissolved oxygen [...]".

 

Source: Earth System Science Data
Authors: Jonathan D. Sharp et al.
DOI: https://doi.org/10.5194/essd-15-4481-2023

Read the full article here.


Paleoenvironmental significance of the carbon isotope record across the Cenomanian–Turonian transition and the Oceanic Anoxic Event 2 (OAE2) ...

Full title: "Paleoenvironmental significance of the carbon isotope record across the Cenomanian–Turonian transition and the Oceanic Anoxic Event 2 (OAE2) in the southeastern Neotethys, Zagros, Iran"

Abstract.

"A high–resolution carbon isotope record of pelagic carbonates (δ13Ccarb) from the Zagros Mountains, Iran, documents a 1.8‰ positive carbon isotope excursion (CIE) in the southeastern Neotethys during the Cenomanian–Turonian transition, corresponding to Ocean Anoxic Event (OAE2). The succession is controlled by biostratigraphy that includes the Rotalipora cushmani [...]".

 

Source: Science Direct
Authors: Borhan Bagherpour et al.
DOI: https://doi.org/10.1016/j.cretres.2023.105574

Read the full article here.


Driver of eustatic change during the early Aptian Oceanic Anoxic Event 1a (∼120 Ma)

Abstract.

"Sea-level changes exert an important control on oceanic circulation and climate evolution. Researchers have proposed that sea-level rise favored accumulation of sediments enriched in organic carbon during oceanic anoxic events (OAEs), although high-frequency sea-level changes and their controlling mechanism have remained poorly constrained. Here we present a detailed sedimentological and geochemical study on Aptian (Lower Cretaceous) shallow-water carbonates of the Dariyan Formation exposed in the Zagros fold belt of southern Iran. [...]".

 

Source: Science Direct
Authors: Yiwei Xu et al.
DOI: https://doi.org/10.1016/j.gloplacha.2023.104236

Read the full article here.


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