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Drivers and Potential Consequences of Observed Extreme Hypoxia Along the Canadian Pacific Continental Shelf

Abstract. 

"Bottom waters of the northeast Pacific continental shelf naturally experience localized hypoxic conditions, with significant influences on food webs and biogeochemical cycling. In August 2021, extreme hypoxia was detected from several measurement platforms along the southern British Columbia continental shelf, with oxygen concentration <60 μmol kg−1, and a difference from the seasonal climatology of more than 2 standard deviations. Early and intense remote upwelling and local density shifts were associated with an anomalously strong spring phytoplankton bloom, which likely stimulated localized respiration of subsurface organic matter. [...]".

 

Source: Wiley Online Library 
Authors: Ana C. Franco et al.
DOI: https://doi.org/10.1029/2022GL101857

Read the full article here.


Early detection of anthropogenic climate change signals in the ocean interior

Abstract. 

"Robust detection of anthropogenic climate change is crucial to: (i) improve our understanding of Earth system responses to external forcing, (ii) reduce uncertainty in future climate projections, and (iii) develop efficient mitigation and adaptation plans. Here, we use Earth system model projections to establish the detection timescales of anthropogenic signals in the global ocean through analyzing temperature, salinity, oxygen, and pH evolution from surface to 2000 m depths. For most variables, anthropogenic changes emerge earlier in the interior ocean than at the surface, due to the lower background variability at depth. [...]".

 

Source: Nature 
Authors: Jerry F. Tjiputra et al.
DOI: https://doi.org/10.1038/s41598-023-30159-0

Read the full article here.


Aquatic Productivity under Multiple Stressors

Abstract. 

"Aquatic ecosystems are responsible for about 50% of global productivity. They mitigate climate change by taking up a substantial fraction of anthropogenically emitted CO2 and sink part of it into the deep ocean. Productivity is controlled by a number of environmental factors, such as water temperature, ocean acidification, nutrient availability, deoxygenation and exposure to solar UV radiation. Recent studies have revealed that these factors may interact to yield additive, synergistic or antagonistic effects. While ocean warming and deoxygenation are supposed to affect mitochondrial respiration oppositely [...]".

 

Source: MDPI
Authors: Donat-P. Häder & Kunshan Gao
DOI: https://doi.org/10.3390/w15040817

Read the full article here.


Pathways of N2O production by marine ammonia-oxidizing archaea determined from dual-isotope labeling

Abstract. 

"The ocean is a net source of the greenhouse gas and ozone-depleting substance, nitrous oxide (N2O), to the atmosphere. Most of that N2O is produced as a trace side product during ammonia oxidation, primarily by ammonia-oxidizing archaea (AOA), which numerically dominate the ammonia-oxidizing community in most marine environments. The pathways to N2O production and their kinetics, however, are not completely understood. Here, we use 15N and 18O isotopes to determine the kinetics of N2O production and trace the source of nitrogen (N) and oxygen (O) atoms in N2O produced by a model marine AOA species, Nitrosopumilus maritimus. [...]".

 

Source: Proceedings of the National Academy of Sciences
Authors: Xianhui S. Wan et al.
DOI: https://doi.org/10.1073/pnas.2220697120

Read the full article here.


Climate Change Impacts on Dissolved Oxygen Concentration in Marine and Coastal Waters around the UK and Ireland

Abstract. 

"What is already happening

  • Since the 1960s, the global oceanic oxygen content has declined by more than 2%.
  • Sustained observations in the North Sea reveal the recent onset of oxygen deficiency in late summer, partly due to ocean warming. The intensity and extent of oxygen deficiency has also increased over time. [...]".

 

Source: Marine Climate Change Impacts Partnership  
Authors: Claire Mahaffey et al.
DOI: 10.14465/2023.reu07.oxy

Read the full article here.


Arctic deep-water anoxia and its potential role for ocean carbon sink during glacial periods

Abstract. 

"Deep water freshening beneath pan-Arctic ice shelves has recently been proposed based on the absence of excess thorium in glacial Arctic sediments. This profound proposal requires scrutiny of Arctic paleohydrology during past glacial periods. Here, we present structural and geochemical results of inorganic authigenic carbonates in deep-sea glacimarine sediments from the Mendeleev Ridge, western Arctic Ocean over the last 76 kyr. Our results suggest that Polar Deep Water in the western Arctic became brackish and anoxic during stadial periods. We argue that sediment-laden hyperpycnal meltwater discharged from paleo-ice sheets filled much of the water column [...]".

 

Source: Nature 
Authors: Kwangchul Jang et al.
DOI: https://doi.org/10.1038/s43247-023-00708-6

Read the full article here.


GO2NE Webinar on Ocean Deoxygenation

GO2NE Webinar on Ocean Deoxygenation. 

"Do you want to know more about deoxygenation in the ocean?
Join us for the upcoming webinar!

Tuesday, 21st March 2023, 16:00 h – 17:00 CET

Registration link

Please join the Global Ocean Oxygen Network (IOC Expert Working Group GO2NE) for a new session of its webinar series on ocean deoxygenation. The 19th webinar will take place 21 March 2023, 16:00 h CET. The webinar will feature presentations by a more senior and an early-career scientist, 20 minutes each followed by 10 minutes moderated discussion sessions. 

If you are interested to present at one of the upcoming webinars please submit a short abstract here.

Moderation
Andreas Oschlies
GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany

Speakers:
Haichao Guo
GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany
"Can oxygen utilization rates track the long-term trend of mesopelagic respiration"

Javier Arístegui
Instituto de Oceanografía y Cambio Global, Universidad de Las Palmas de Gran Canaria, Spain
"Estimating dark-ocean respiration through ETS activity" 

If you want to receive further information about upcoming webinars please register here." 


../common/calendar Start Date: 3/21/23

Global ocean redox changes before and during the Toarcian Oceanic Anoxic Event

Abstract. 

"Mesozoic oceanic anoxic events are recognized as widespread deposits of marine organic-rich mudrocks temporally associated with mass extinctions and large igneous province emplacement. The Toarcian Oceanic Anoxic Event is one example during which expanded ocean anoxia is hypothesized in response to environmental perturbations associated with emplacement of the Karoo–Ferrar igneous province. However, the global extent of total seafloor anoxia and the relative extent of euxinic (anoxic and sulfide-rich) and non-euxinic anoxic conditions during the Toarcian Oceanic Anoxic Event are poorly constrained. [...]".

 

Source: Nature
Authors: Alexandra Kunert & Brian Kendall
DOI: https://doi.org/10.1038/s41467-023-36516-x

Read the full article here.


Physiological and gene expression responses of the mussel Mytilus galloprovincialis to low pH and low dissolved oxygen

Abstract. 

"The prevalence and frequency of hypoxia events have increased worldwide over the past decade as a consequence of global climate change and coastal biological oxygen depletions. On the other hand, anthropogenic emissions of CO2 and consequent accumulation in the sea surface result in a perturbation of the seawater carbonate system, including a decrease in pH, known as ocean acidification. While the effect of decreases in pH and dissolved oxygen (DO) concentration is better understood, their combined effects are still poorly resolved. [...]". 

 

Source: Science Direct 
Authors: Murat Belivermiş et al.
DOI: https://doi.org/10.1016/j.marpolbul.2023.114602

Read the full article here.


Editorial: Regional coastal deoxygenation and related ecological and biogeochemical modifications in a warming climate

Abstract. 

"Coastal ecosystems play tremendous roles in socio-economic development, but their functions are degrading due to human activities. One of the most alarming degradations is coastal deoxygenation, driven primarily by the over-enrichment of anthropogenic nutrients and organic matter (eutrophication) in the coastal waters. The coastal deoxygenation has led to the worldwide spread of hypoxic zones (where dissolved oxygen concentration is less than 2 mg/L), with the number of reported hypoxic sites increasing from 45 in the 1960s to around 700 nowadays. Besides being perturbed by human activities locally, coastal waters respond more rapidly than [...]".

 

Source: Frontiers 
Authors: Wenxia Zhang et al.
DOI: https://doi.org/10.3389/fmars.2023.1146877

Read the full article here.


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