Processes controlling the redox budget for the oxic/anoxic water column of the Black Sea

Konovalov, Sergey; Murray, James; Luther, George W.; Tebo, Bradley M.

doi:10.1016/j.dsr2.2006.03.013

Cited by 64 publications

(52 citation statements)

References 61 publications

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“…This excludes the possibility that subsurface oxygen maximum is just a direct consequence of the oxygen-rich water created by winter convection, which remains overlain in summer by the low-oxygen (because of the high SST) surface water. The observed absolute oxygen maximum in the subsurface layers is consistent with the findings of Yakushev et al (2007), Konovalov et al (2006) and Gregoire and Soetart (2010) oxygen in the Black Sea was due to phytoplankton, which shows larger production in summer.…”

Section: Comparison Between the Numerical Simulations And Observationssupporting

confidence: 89%

Mixing in the Black Sea detected from the temporal and spatial variability of oxygen and sulfide – Argo float observations and numerical modelling

et al. 2014

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Abstract. The temporal and spatial variability of the upper ocean hydrochemistry in the Black Sea is analysed using data originating from profiling floats with oxygen sensors and carried out with a coupled three-dimensional circulationbiogeochemical model including 24 biochemical state variables. Major focus is on the dynamics of suboxic zone which is the interface separating oxygenated and anoxic waters. The scatter of oxygen data seen when plotted in density coordinates is larger than those for temperature, salinity and passive tracers. This scatter is indicative of vigorous biogeochemical reactions in the suboxic zone, which acts as a boundary layer or internal sink for oxygen. This internal sink affects the mixing patterns of oxygen compared to the ones of conservative tracers. Two different regimes of ventilation of pycnocline were clearly identified: a gyre-dominated (cyclonic) regime in winter and a coastal boundary layer (anticyclonic eddy)-dominated regime in summer. These contrasting states are characterized by very different pathways of oxygen intrusions along the isopycnals and vertical oxygen conveyor belt organized in multiple-layered cells formed in each gyre. The contribution of the three-dimensional modelling to the understanding of the Black Sea hydro-chemistry, and in particular the coast-to-open-sea mixing, is also demonstrated. Evidence is given that the formation of oxic waters and of cold intermediate waters, although triggered by the same physical process, each follow a different evolution. The difference in the depths of the temperature minimum and the oxygen maximum indicates that the variability of oxygen is not only just a response to physical forcing and changes in the surface conditions, but undergoes its own evolution.

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Section: Comparison Between the Numerical Simulations And Observationssupporting

confidence: 89%

Mixing in the Black Sea detected from the temporal and spatial variability of oxygen and sulfide – Argo float observations and numerical modelling

et al. 2014

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“…Cicerone and Oremland, 1988). Significant progress has been made to incorporate these complex biogeochemical cycles in models of low-oxygen environments in semi-enclosed seas such as the Black Sea (Oguz et al, 2000;Konovalov et al, 2006;Yakushev et al, 2007;Grégoire et al, 2008), but not in other regions (e.g. OMZ).…”

Section: Introductionmentioning

confidence: 99%

Modeling dissolved oxygen dynamics and hypoxia

et al. 2010

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Abstract. Hypoxia conditions are increasing throughout the world, influencing biogeochemical cycles of elements and marine life. Hypoxia results from complex interactions between physical and biogeochemical processes, which can not be understood by observations alone. Models are invaluable tools at studying system dynamics, generalizing discrete observations and predicting future states. They are also useful as management tools for evaluating site-specific responses to management scenarios. Here we review oxygen dynamics models that have significantly contributed to a better understanding of the effects of natural processes and human perturbations on the development of hypoxia, factors controlling the extent and temporal variability of coastal hypoxia, and the effects of oxygen depletion on biogeochemical cycles. Because hypoxia occurs in a variety of environments and can be persistent, periodic or episodic, models differ significantly in their complexity and temporal and spatial resolution. We discuss the progress in developing hypoxia models for benthic and pelagic systems that range from simple box models to three dimensional circulation models. Applications of these models in five major hypoxia regions are presented. In the last decades, substantial progress has been made towards the parameterization of biogeochemical processes in both hypoxic water columns and sediments. In coastal regions, semiempirical models have been used more frequently than mechanistic models to study nutrient enrichment and hypoxia relationships. Recent advances in three-dimensional coupled physical-ecological-biogeochemical models have allowed a better representation of physical-biological interactions in these systems. We discuss the remaining gaps in process deCorrespondence to: M. A. Peña (angelica.pena@dfo-mpo.gc.ca) scriptions and suggest directions for improvement. Better process representations in models will help us answer several important questions, such as those about the causes of the observed worldwide increase in hypoxic conditions, and future changes in the intensity and spread of coastal hypoxia. At the same time, quantitative model intercomparison studies suggest that the predictive ability of our models may be adversely affected by their increasing complexity, unless the models are properly constrained by observations.

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“…In recent years, much insight has been gained into the biogeochemical and physical processes driving the oxygen distribution in the Black Sea and its variability (e.g., Konovalov and Murray, 2001;Konovalov et al, 2003Konovalov et al, , 2005Konovalov et al, , 2006Glazer et al, 2006). Two important questions concerning the long-term (decadal) variations in oxygen distribution that still remain open are related to identifying the main drivers and distinguishing between the influence of climate change and the influence of direct anthropogenic pressure (eutrophication).…”

Section: Multidecadal Hypoxia Trends In Stratified Basinsan Example Fmentioning

confidence: 99%

Investigating hypoxia in aquatic environments: diverse approaches to addressing a complex phenomenon

et al. 2014

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Abstract. In this paper we provide an overview of new knowledge on oxygen depletion (hypoxia) and related phenomena in aquatic systems resulting from the EU-FP7 project HYPOX ("In situ monitoring of oxygen depletion in hypoxic ecosystems of coastal and open seas, and landlocked water bodies", www.hypox.net). In view of the anticipated oxygen loss in aquatic systems due to eutrophication and climate change, HYPOX was set up to improve capacities to monitor hypoxia as well as to understand its causes and consequences.Temporal dynamics and spatial patterns of hypoxia were analyzed in field studies in various aquatic environments, including the Baltic Sea, the Black Sea, Scottish and Scandinavian fjords, Ionian Sea lagoons and embayments, and Swiss lakes. Examples of episodic and rapid (hours) occurrences of hypoxia, as well as seasonal changes in bottom-water oxygenation in stratified systems, are discussed. Geologically driven hypoxia caused by gas seepage is demonstrated. Using novel technologies, temporal and spatial patterns of watercolumn oxygenation, from basin-scale seasonal patterns to meter-scale sub-micromolar oxygen distributions, were resolved. Existing multidecadal monitoring data were used to demonstrate the imprint of climate change and eutrophication on long-term oxygen distributions. Organic and inorganic proxies were used to extend investigations on past oxygen conditions to centennial and even longer timescales that cannot be resolved by monitoring. The effects of hypoxia on faunal communities and biogeochemical processes were also addressed in the project. An investigation of benthic fauna is presented as an example of hypoxia-devastated benthic communities that slowly recover upon a reduction in eutrophication in a system where naturally occurring hypoxia overlaps with anthropogenic hypoxia. Biogeochemical investigations reveal that oxygen intrusions have a strong effect on the microbially mediated redox cycling of elements. Observations and modeling studies of the sediments demonstrate the effect of seasonally changing oxygen conditions on benthic mineralization pathways and fluxes. Data quality and access are crucial in hypoxia research. Technical issues are therefore also addressed, including the availability of suitable sensor technology to resolve the gradual changes in bottom-water oxygen in marine systems that can be expected as a result of climate change. Using cabled observatories as examples, we show how the benefit of continuous oxygen monitoring can be maximized by adopting proper quality control. Finally, we discuss strategies for state-of-the-art data archiving and dissemination in compliance with global standards, and how ocean observations can contribute to global earth observation attempts.

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Processes controlling the redox budget for the oxic/anoxic water column of the Black Sea

Cited by 64 publications

References 61 publications

Mixing in the Black Sea detected from the temporal and spatial variability of oxygen and sulfide – Argo float observations and numerical modelling

Mixing in the Black Sea detected from the temporal and spatial variability of oxygen and sulfide – Argo float observations and numerical modelling

Modeling dissolved oxygen dynamics and hypoxia

Investigating hypoxia in aquatic environments: diverse approaches to addressing a complex phenomenon

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