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Climatic Changes in North Atlantic O2 Amplified by Temperature Sensitivity of Phytoplankton Growth

Abstract.

"Ocean warming is associated with a decline in the global oxygen (O2) inventory, but the ratio of O2 loss to heat gain is poorly understood. We analyzed historical variability in temperature (T), O2, and nitrate (N⁢O3−) in hydrographic observations and model simulations of the North Atlantic, a relatively well-sampled region that is important for deep ocean ventilation. Multidecadal fluctuations of O2 concentrations in subpolar thermocline waters (100–700 m) are correlated with changes in their heat content, with a slope 35% steeper than that expected from thermal solubility. [...]".

 

Source: Wiley Online Library
Authors: Andrew J. Margolskee et al.
DOI: https://doi.org/10.1029/2023GB007930

Read the full article here.


Preprint: Evolution of oxygen and stratification in the North Pacific Ocean in CMIP6 Earth System Models

Abstract.

"This study examines the linkages between the upper ocean (0–200 m) oxygen (O2) content and stratification in the North Pacific Ocean in four Earth system models (ESMs), an ocean hindcast simulation, and ocean reanalysis data. Trend and variability of oceanic O2 content are driven by the imbalance between physical supply and biological demand. The physical supply is primarily controlled by ocean ventilation, which is responsible for the transport of O2-rich surface waters into subsurface. To quantify the ocean ventilation, Isopycnic Potential Vorticity (IPV) is used as a dynamical proxy in this study. [...]".

 

Source: Biogeosciences
Authors: Lyuba Novi et al.
DOI: https://doi.org/10.5194/bg-2023-129

Read the full article here.


Linking northeastern North Pacific oxygen changes to upstream surface outcrop variations

Abstract.

"Understanding the response of the ocean to global warming, including the renewal of ocean waters from the surface (ventilation), is important for future climate predictions. Oxygen distributions in the ocean thermocline have proven an effective way to infer changes in ventilation because physical processes (ventilation and circulation) that supply oxygen are thought to be primarily responsible for changes in interior oxygen concentrations. Here, the focus is on the North Pacific thermocline, where some of the world's oceans' largest oxygen variations have been observed. [...]".

 

Source: Biogeosciences
Authors: Sabine Mecking & Kyla Drushka
DOI: https://doi.org/10.5194/bg-21-1117-2024

Read the full article here.


Do phytoplankton require oxygen to survive? A hypothesis and model synthesis from oxygen minimum zones

Abstract. 

"It is commonly known that phytoplankton have a pivotal role in marine biogeochemistry and ecosystems as carbon fixers and oxygen producers, but their response to deoxygenation has scarcely been studied. Nonetheless, in the major oceanic oxygen minimum zones (OMZs), all surface phytoplankton groups, regardless of size, disappear and are replaced by unique cyanobacteria lineages below the oxycline. To develop reasonable hypotheses to explain this pattern, we conduct a review of available information on OMZ phytoplankton, and we re-analyze previously published data (flow cytometric and hydrographic) [...]". 

 

Source: Wiley Online Library
Authors: Jane C. Y. Wong et al.
DOI: https://doi.org/10.1002/lno.12367

Read the full article here.


Nitrite Oxidation Across the Full Oxygen Spectrum in the Ocean

Abstract. 

"Fixed nitrogen limits primary productivity in most areas of the surface ocean. Nitrite oxidation is the main source of nitrate, the most abundant form of inorganic fixed nitrogen. Even though known as an aerobic process, nitrite oxidation is not always stimulated by increased oxygen concentration, and nitrite oxidation occurs in layers of oxygen minimum zones (OMZs) where oxygen is not detectable. Nitrite-oxidizing bacteria, known since their original isolation as aerobes, were also detected in these layers. Whether and how nitrite oxidation is occurring in the anoxic seawater is debated. [...]".

 

Source: Wiley Online Library 
Authors: Xin Sun et al.
DOI: https://doi.org/10.1029/2022GB007548

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.


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