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Benthic fluxes of oxygen and heat from a seasonally hypoxic region of Saanich Inlet fjord observed by eddy covariance

Abstract.

"Benthic habitats within fjords are predominantly insulated from the high energy physical dynamics of open coastlines. As a result, fjords may have atypical mass and heat transfer rates at the seafloor. This study presents aquatic eddy covariance (EC) measurements made continuously from late May 2013 through December 2013, in Saanich Inlet fjord, British Columbia, to assess areal-averaged benthic fluxes of dissolved oxygen and heat, and their relationships to bottom boundary layer dynamics and water properties. The measurements were achieved by the connection of a system of underwater EC sensors to Ocean Network Canada's Victoria Experimental Network Under the Sea (VENUS) observatory that has a primary seafloor node[...]"

 

Source: Science Direct
Authors: Clare E. Reimers et al.
DOI: https://doi.org/10.1016/j.ecss.2020.106815

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Recovery from multi-millennial natural costal hypoxia in the Stockholm Archipelago, Baltic Sea, terminated by modern human activity

Abstract.

"Enhanced nutrient input and warming have led to the development of low oxygen (hypoxia) in coastal waters globally. For many coastal areas, insight into redox conditions prior to human impact is lacking. Here, we reconstructed bottom water redox conditions and sea surface temperatures (SSTs) for the coastal Stockholm Archipelago over the past 3000 yr. Elevated sedimentary concentrations of molybdenum indicate (seasonal) hypoxia between 1000 b.c.e. and 1500 c.e. Biomarker[...]"

 

Source: ASsociation for the Sciences of Limnology and Oceanography
Authors: Niels A. G. M. van Helmond et al.
DOI: https://doi.org/10.1002/lno.11575

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Impacts of climate change on dissolved oxygen concentration relevant to the costal and marine environment around the UK

Abstract.

"The decline in dissolved oxygen and onset of oxygen deficiency and hypoxia are naturally occurring phenomenon in aquatic environments, typically occurring on seasonal timescales. Over decadal timescales, there has been a measurable decline in dissolved oxygen concentrations in the global ocean due to warming caused by anthropogenic activity. Approximately 15% of the global decline in oxygen has been attributed to reduced solubility in response to ocean warming, with the remaining 85% due to intensified stratification. The relative contribution of these factors in coastal and shelf-sea waters is currently unknown. In UK waters, sustained observations in the North[...]"

 

Source: MCCIP Science Review
Authors: Mahaffey, C et al.
DOI: https://doi.org/10.14465/2020.arc02.oxy

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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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Dissolved oxygen and pH criteria leave fisheries at risk

Abstract.

"Changes in human population centers and agricultural fertilizer use have accelerated delivery rates of nitrogen and phosphorus to coastal waters, often stimulating rapid accumulations of primary production (1). Whereas resulting eutrophication processes are of less environmental relevance in well-mixed, ocean ecosystems, when they occur in warm, stratified, and/or poorly mixed waters, they can result in hypoxia [depletion of dissolved oxygen (DO)] and acidification (decrease in pH), both of which individually can have adverse effects on aquatic life, affecting a suite of physiological processes and increasing mortality rates (23). [...]"

Source: Science
Authors: Stephen J. Tomasetti, Christopher J. Gobler
DOI: 10.1126/science.aba4896

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Physical preconditioning of oxygen depletion in shelf seas

Abstract.

"The global ocean dissolved oxygen (DO) inventory is decreasing and the areal extent of DO deficiency is increasing. In the shelf sea BML, net DO removal can occur as a result of restricted ventilation due to seasonal thermal stratification, oxygen consumption via pelagic and benthic respiration of organic matter, and nitrification. DO decline is becoming evident in several shelf seas, with recent model studies estimating that large regions of the Northwest European continental shelf seas (325,000 to 400,000 km2) have the potential to become seasonally deficient in DO in late summer. It is therefore of vital importance that DO is monitored accurately and effectively in shelf seas. [...]"

Source: EGU General Assembly 2020
Authors: Charlotte Williams et al.
DOI: 10.5194/egusphere-egu2020-20219

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Effects of hypoxia on the behavior and physiology of kelp forest fishes

Abstract.

"Forecasts from climate models and oceanographic observations indicate increasing deoxygenation in the global oceans and an elevated frequency and intensity of hypoxic events in the coastal zone, which have the potential to affect marine biodiversity and fisheries. Exposure to low dissolved oxygen (DO) conditions may have deleterious effects on early life stages in fishes.  [...]"

Source: Global Change Biology
Authors: Evan G. Mattiasen et al.
DOI: 10.1111/gcb.15076

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Global certified-reference-material- or reference-material-scaled nutrient gridded dataset GND13

Abstract.

"A global nutrient gridded dataset that might be the basis for studies of more accurate spatial distributions of nutrients in the global ocean was created and named GND13. During 30 cruises, reference materials of nutrients in seawater or their equivalents were used at all stations, and high-precision measurements were made. The precision of the nutrient analyses was better than 0.2 %. Data were collected from the hydrographic cruises in the JASMTEC R/V Mirai cruises, JMA cruise, CARINA, PACIFICA, and WGHC datasets from which nutrient data were available. [...]"

Source: Earth System Science Data
Authors: Michio Aoyama
DOI: 10.5194/essd-12-487-2020

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Application of geoacoustic inference to assess the diurnal effects of photosynthetic activity in a seagrass meadow

Abstract.

"Seagrasses provide a multitude of ecosystem services: they alter water flow, cycle nutrients, stabilize sediments, support the food web structure, and provide a critical habitat for many animals. However, due to threats to seagrass meadows and their associated ecosystems, these habitats are declining globally. Acoustical methods can be a powerful remote sensing tool to efficiently monitor seagrass meadows, alleviating the problem of space and time aliasing associated with traditional spot measurements. [...]"

Source: Earth and Space Science Open Archive
Authors: Megan Ballard et al.
DOI: 10.1002/essoar.10502265.1

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Observed spatiotemporal variation of three-dimensional structure and heat/salt transport of anticyclonic mesoscale eddy in Northwest Pacific

Abstract.

"As in-situ observations are sparse, targeted observations of a specific mesoscale eddy are rare. Therefore, it is difficult to study the three-dimensional structure of moving mesoscale eddies. From April to September 2014, an anticyclonic eddy located at 135°E–155°E, 26°N–42°N was observed using 17 rapid-sampling Argo floats, and the spatiotemporal variations in the three-dimensional structure were studied. [...]"

Source: Journal of Oceanology and Limnology
Authors: Jun Dai et al.
DOI: 10.1007/s00343-019-9148-z

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