Authigenic uranium deposition in the glacial North Atlantic: Implications for changes in oxygenation, carbon storage, and deep water-mass geometry


"Oxygen in the ocean has essential ecological and climatic functions, and can be an important indicator of deep-ocean ventilation and carbon storage. Previous studies are divided on whether the subsurface North Atlantic, which today is well-oxygenated, had higher or lower oxygen levels during the Last Glacial Maximum (LGM). Crucially, the limited number of previous reconstructions precludes any conclusions regarding basin-wide patterns in past changes in oxygenation. [...]".


Source: Science Direct 
Authors: Yuxin Zhou & Jerry F. McManus

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The Peruvian oxygen minimum zone was similar in extent but weaker during the Last Glacial Maximum than Late Holocene


"Quantifying past oxygen concentrations in oceans is crucial to improving understanding of current global ocean deoxygenation. Here, we use a record of pore density of the epibenthic foraminifer Planulina limbata from the Peruvian Oxygen Minimum Zone to reconstruct oxygen concentrations in bottom waters from the Last Glacial Maximum to the Late Holocene at 17.5°S about 500 meters below the sea surface. We found that oxygen levels were 40% lower during the Last Glacial Maximum than during the Late Holocene (about 6.7 versus 11.1 µmol/kg, respectively). [...]".


Source: Nature
Authors: Nicolaas Glock et al. 

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A three-dimensional model of the marine nitrogen cycle during the Last Glacial Maximum constrained by sedimentary isotopes


"Nitrogen is a key limiting nutrient that influences marine productivity and carbon sequestration in the ocean via the biological pump. In this study, we present the first estimates of nitrogen cycling in a coupled 3D ocean-biogeochemistry-isotope model forced with realistic boundary conditions from the Last Glacial Maximum (LGM) ~21,000 years before present constrained by nitrogen isotopes. The model predicts a large decrease in nitrogen loss rates due to higher oxygen concentrations in the thermocline and sea level drop, and, as a response, reduced nitrogen fixation. Model experiments are performed to evaluate effects of hypothesized increases of atmospheric iron fluxes and oceanic phosphorus inventory relative to present-day conditions. [...]"

Source: Frontiers in Marine Science
Authors: Christopher J. Somes et al.
DOI: 10.3389/fmars.2017.00108

Full article


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