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Latitudinal gradient in the respiration quotient and the implications for ocean oxygen availability

Abstract.

"Climate-driven depletion of ocean oxygen strongly impacts the global cycles of carbon and nutrients as well as the survival of many animal species. One of the main uncertainties in predicting changes to marine oxygen levels is the regulation of the biological respiration demand associated with the biological pump. Derived from the Redfield ratio, the molar ratio of oxygen to organic carbon consumed during respiration (i.e., the respiration quotient, r −O2:C  r−O2:C ) is consistently assumed constant but rarely, if ever, measured. Using a prognostic[...]"

 

Source: Proceedings of the National Academy of Sciences of the United States of America
Authors: Allison R. Moreno et al.
DOI:  https://doi.org/10.1073/pnas.2004986117

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The Northeast Atlantic is running out of excess carbonate in the horizon of cold-water corals communities

Abstract.

"The oceanic uptake of atmospheric carbon dioxide (CO2) emitted by human activities alters the seawater carbonate system. Here, the chemical status of the Northeast Atlantic is examined by means of a high-quality database of carbon variables based on the GO-SHIP A25 section (1997–2018). The increase of atmospheric CO2 leads to an increase in ocean anthropogenic carbon (Cant) and a decrease in carbonate that is unequivocal in the upper and mid-layers (0–2,500 m depth). In the mid-layer, the carbonate content in the Northeast Atlantic is maintained by the interplay between the northward spreading of recently conveyed Mediterranean Water with excess of carbonate and the arrival of subpolar-origin waters close to carbonate[...]".

Source: Nature Reviews Earth & Environment
Authors: Marcos Fontela et al.
DOI: https://doi.org/10.1038/s41598-020-71793-2

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Contrasting Upper and Deep Ocean Oxygen Response to Protracted Global Warming

Abstract.

"It is well established that the ocean is currently losing dissolved oxygen (O2) in response to ocean warming, but the long‐term, equilibrium response of O2 to a warmer climate is neither well quantified nor understood. Here we use idealized multimillennial global warming simulations with a comprehensive Earth system model to show that the equilibrium response in ocean O2 differs fundamentally from the ongoing transient response. After physical equilibration of the model (>4,000 years) under a two times preindustrial CO2 scenario, the deep ocean[...]"

Source: Advancing Earth and Space Science
Authors: T. L. Frölicher et al.
DOI: https://doi.org/10.1029/2020GB006601

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Substrate regulation leads to differential responses of microbial ammonia-oxidizing communities to ocean warming

Abstract.

"In the context of continuously increasing anthropogenic nitrogen inputs, knowledge of how ammonia oxidation (AO) in the ocean responds to warming is crucial to predicting future changes in marine nitrogen biogeochemistry. Here, we show divergent thermal response patterns for marine AO across a wide onshore/offshore trophic gradient. [...]"

Source: Nature Communications
Authors: Zhen-Zhen Zheng et al.
DOI: 10.1038/s41467-020-17366-3

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Twenty-first century ocean warming, acidification, deoxygenation, and upper-ocean nutrient and primary production decline from CMIP6 model projections

Abstract.

"Anthropogenic climate change is projected to lead to ocean warming, acidification, deoxygenation, reductions in near-surface nutrients, and changes to primary production, all of which are expected to affect marine ecosystems. Here we assess projections of these drivers of environmental change over the twenty-first century from Earth system models (ESMs) participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6) that were forced under the CMIP6 Shared Socioeconomic Pathways (SSPs). [...]"

Source: Biogeosciences
Authors: Lester Kwiatkowski et al.
DOI: 10.5194/bg-17-3439-2020

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Is deoxygenation detectable before warming in the thermocline?

Abstract.

"Anthropogenic greenhouse gas emissions cause ocean warming and oxygen depletion, with adverse impacts on marine organisms and ecosystems. Warming is one of the main indicators of anthropogenic climate change, but, in the thermocline, changes in oxygen and other biogeochemical tracers may emerge from the bounds of natural variability prior to warming. Here, we assess the time of emergence (ToE) of anthropogenic change in thermocline temperature and thermocline oxygen within an ensemble of Earth system model simulations from the fifth phase of the Coupled Model Intercomparison Project. [...]"

Source: Biogeosciences
Authors: Angélique Hameau et al.
DOI: 10.5194/bg-17-1877-2020

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Warming stimulates sediment denitrification at the expense of anaerobic ammonium oxidation

Abstract.

"Temperature is one of the fundamental environmental variables governing microbially mediated denitrification and anaerobic ammonium oxidation (anammox) in sediments. The GHG nitrous oxide (N2O) is produced during denitrification, but not by anammox, and knowledge of how these pathways respond to global warming remains limited. [...]"

Source: Nature Climate Change
Authors: Ehui Tan et al.
DOI: 10.1038/s41558-020-0723-2

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HKU study shows that control of anthropogenic atmospheric emissions can improve water quality in China’s coastal Seas

"A new research led by MPhil student Miss Yu Yan Yau and supervised by Dr Benoit Thibodeau from the Department of Earth Sciences and the Swire Institute of Marine Science, the University of Hong Kong (HKU), highlighted the importance of reducing fossil fuel combustion not only to curb the trend of global warming, but also to improve the quality of China’s coastal waters. The findings were recently published in the prestigious journal Environmental Science & Technology. [...]"

Source: The University of Hong Kong

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Our Vanishing World: Oceans

"As the human onslaught against life on Earth accelerates, no part of the biosphere is left pristine. The simple act of consuming more than we actually need drives the world’s governments and corporations to endlessly destroy more and more of the Earth to extract the resources necessary to satisfy our insatiable desires. In fact, an initiative of the World Economic Forum has just reported that ‘For the first time in history, more than 100 billion tonnes of materials are entering the global economy every year’ – see ‘The Circularity Gap Report 2020’– which means that, on average, every person on Earth uses more than 13 tonnes of materials each year extracted from the Earth. [...]"

Source: GlobalReasearch

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Multi-agency report highlights increasing signs and impacts of climate change in atmosphere, land and oceans

"New York / Geneva, 10 March 2020 - The tell-tale physical signs of climate change such as increasing land and ocean heat, accelerating sea level rise and melting ice are highlighted in a new report compiled by the World Meteorological Organization and an extensive network of partners. It documents impacts of weather and climate events on socio-economic development, human health, migration and displacement, food security and land and marine ecosystems. [...]"

Source: World Meteorological Organization (WMO)

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