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The Equatorial Undercurrent and the Oxygen Minimum Zone in the Pacific

Abstract.

"Warming‐driven expansion of the oxygen minimum zone (OMZ) in the equatorial Pacific would bring very low oxygen waters closer to the ocean surface, and possibly impact global carbon/nutrient cycles and local ecosystems. Global coarse Earth System Models (ESMs) show, however, disparate trends that poorly constrain these future changes in the upper OMZ. [...]"

Source: Geophysical Research Letters
Authors: Julius J.M. Busecke, Laure Resplandy and John P. Dunne
DOI: 10.1029/2019GL082692

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Diapycnal dissolved organic matter supply into the upper Peruvian oxycline

Abstract.

"The eastern tropical South Pacific (ETSP) hosts the Peruvian upwelling system, which represents one of the most productive areas in the world ocean. High primary production followed by rapid heterotrophic utilization of organic matter supports the formation of one of the most intense oxygen minimum zones (OMZs) in the world ocean, where dissolved oxygen (O2) concentrations reach less than 1 µmol kg−1. [...]"

Source: Biogeosciences
Authors: Alexandra N. Loginova et al.
DOI: 10.5194/bg-16-2033-2019

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Strong intensification of the Arabian Sea oxygen minimum zone in response to Arabian Gulf warming

Abstract.

"The highly saline, oxygen saturated waters of the Arabian Gulf (hereafter the Gulf) sink to intermediate depths (200‐300m) when they enter the Arabian Sea, ventilating the World's thickest oxygen minimum zone (OMZ). Here, we investigate the impacts of a warming of the Gulf consistent with climate change projections on the intensity of this OMZ. Using a series of eddy‐resolving model simulations, we show that the warming of the Gulf waters increases their buoyancy and hence limits their contribution to the ventilation of intermediate depths. [...]"

Source: Geophysical Research Letters
Authors: Z. Lachkar, M. Lévy and S. Smith
DOI: 10.1029/2018GL081631

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Remote and local drivers of oxygen and nitrate variability in the shallow oxygen minimum zone off Mauritania in June 2014

Abstract.

"Upwelling systems play a key role in the global carbon and nitrogen cycles and are also of local relevance due to their high productivity and fish resources. To capture and understand the high spatial and temporal variability in physical and biogeochemical parameters found in these regions, novel measurement techniques have to be combined in an interdisciplinary manner. Here we use high-resolution glider-based physical–biogeochemical observations in combination with ship-based underwater vision profiler, sensor and bottle data to investigate the drivers of oxygen and nitrate variability across the shelf break off Mauritania in June 2014. [...]"

Source: Biogeosciences
Authors: Soeren Thomsen et al.
DOI: 10.5194/bg-16-979-2019

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N2O Emissions From the Northern Benguela Upwelling System

Abstract.

"The Benguela Upwelling System (BUS) is the most productive of all eastern boundary upwelling ecosystems and it hosts a well‐developed oxygen minimum zone. As such, the BUS is a potential hotspot for production of N2O, a potent greenhouse gas derived from microbially driven decay of sinking organic matter. Yet, the extent at which near‐surface waters emit N2O to the atmosphere in the BUS is highly uncertain. [...]"

Source: Geophysical Research Letters
Authors: D. L. Arévalo‐Martínez et al.
DOI: 10.1029/2018GL081648

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Yield stability analysis reveals sources of large-scale nitrogen loss from the US Midwest

Abstract.

"Loss of reactive nitrogen (N) from agricultural fields in the U.S. Midwest is a principal cause of the persistent hypoxic zone in the Gulf of Mexico. We used eight years of high resolution satellite imagery, field boundaries, crop data layers, and yield stability classes to estimate the proportion of N fertilizer removed in harvest (NUE) versus left as surplus N in 8 million corn (Zea mays) fields at subfield resolutions of 30 × 30 m (0.09 ha) across 30 million ha of 10 Midwest states. [...]"

Source: Scientific Reports
Authors: Bruno Basso et al.
DOI: 10.1038/s41598-019-42271-1

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Assessment of the impact of spatial resolution on ROMS simulated upper-ocean biogeochemistry of the Arabian Sea from an operational perspective

Abstract.

"The resolution of the model emerges to be an important factor in simulating the real oceanic features. In this paper, the performance of two coupled bio-physical models, having spatial resolutions 1/12° (∼9 km) and 1/4° (∼25 km) configured using Regional Ocean Modeling System (ROMS), have been evaluated in simulating upper ocean dynamics of the Arabian Sea. [...]"

Source: Journal of Operational Oceanography
Authors: Kunal Chakraborty et al.
DOI: 10.1080/1755876X.2019.1588697

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Microbial ecosystem dynamics drive fluctuating nitrogen loss in marine anoxic zones

Abstract.

"The dynamics of nitrogen (N) loss in the ocean’s oxygen-deficient zones (ODZs) are thought to be driven by climate impacts on ocean circulation and biological productivity. Here we analyze a data-constrained model of the microbial ecosystem in an ODZ and find that species interactions drive fluctuations in local- and regional-scale rates of N loss, even in the absence of climate variability. [...]"

Source: PNAS
Authors: Justin L. Penn et al.
DOI: 10.1073/pnas.1818014116

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Diversity of culturable Sulphur-oxidising bacteria in the oxygen minimum zones of the northern Indian Ocean

Abstract.

"Oxygen minimum zones (OMZs) are unique, widely spread and well-studied features of the global ocean, varying in seasonality and intensity. The Northern Indian Ocean contains OMZs in the Arabian Sea (AS-OMZ) and the Bay of Bengal (BB-OMZ) having unique biogeochemical features. OMZ water column harbours distinct microbial communities that play vital roles in ocean biogeochemical cycles. Sulphur cycling processes facilitated by OMZ microbial communities are poorly understood with regards to different microbial groups involved, spatially and temporally. [...]"

Source: Journal of Marine Systems (2018)
Authors: Larissa Menezes et al.
DOI: 10.1016/j.jmarsys.2018.05.007

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Nitrogen cycling driven by organic matter export in the South Pacific oxygen minimum zone

Abstract.

"Oxygen minimum zones are expanding globally, and at present account for around 20–40% of oceanic nitrogen loss. Heterotrophic denitrification and anammox—anaerobic ammonium oxidation with nitrite—are responsible for most nitrogen loss in these low-oxygen waters. Anammox is particularly significant in the eastern tropical South Pacific, one of the largest oxygen minimum zones globally. "

Source: Nature Geoscience (2013)
Authors: Tim Kalvelage et al.
DOI: 10.1038/ngeo1739

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