Basin scale spatiotemporal analysis of shoreline change in the Black Sea

An important deoxygenation trend has been described in the Black Sea over the five past decades from in-situ observations [1]. While the implications for basin-scale biogeochemistry and possible future trends of this dynamics are unclear, it is important to consolidate our means to resolve the dynamics of the Black Sea oxygen content in order to assess the likelihood of future evolution scenario, and the possible morphology of low-oxygen events.&#160;Also, it is known that current global models simulate only about half the observed oceanic O2 loss and fail in reproducing its vertical distribution[2]. In parts, unexplained O2 losses could be attributed to illy parameterized biogeochemical processes within 3D models used to integrate those multi-elemental dynamics.Biogeochemical processes involved in O2 dynamics are structured vertically and well separated in the stratified Black Sea. O2 sources proceed from air-sea fluxes and photosynthesis in the photic zone. Organic matter (OM) is respired over a depth determined by its composition and sinking, via succeeding redox reactions. Those intricate dynamics leave unknowns as regards the biogeochemical impacts of future deoxygenation on associated cycles, for instance on the oceanic carbon pump. Here we use the Black Sea scene to derive model-observation strategies to best address the global deoxygenation concern.First, we decipher components of the O2 dynamics in the open basin, and discuss the way in which O2-based indicators informs on the relative importance of processes involved. Using 1D biogeochemical model set-up, we then conduct a sensitivity analysis to pin-point model parameters, ie. biogeochemical processes, that bears the largest part in the uncertainty of simulated results for those diagnostics. Finally, we identify among the most impacting parameters the ones that can most efficiently be constrained on the basis of modern observational infrastructure, and Bio-Argo in particular.&#160;The whole procedure aims at orienting the development of observations networks and data assimilation approaches in order to consolidate our means to anticipate the marine deoxygenation challenge.&#160;[1] Capet A et al., 2016, Biogeoscience, 13:1287-1297 [2] Oschlies A et al., 2018, Nature Geosci, 11(7):467&#8211;473

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Dynamics of the Deep Chlorophyll Maximum in the Black Sea as depicted by BGC-Argo floats

10.5194/egusphere-egu21-3191 ◽

2021 ◽

Author(s):

Arthur Capet ◽

florian ricour ◽

Fabrizio D'Ortenzio ◽

Bruno Delille ◽

Marilaure Grégoire

Keyword(s):

Black Sea ◽

Global Ocean ◽

The Black Sea ◽

Second Phase ◽

Deep Chlorophyll Maximum ◽

Phytoplankton Productivity ◽

Spatial Homogeneity ◽

Argo Floats ◽

Chlorophyll Maximum ◽

Basin Scale

The deep chlorophyll maximum (DCM) is a well known feature of the global ocean. However, its description and the study of its formation are a&#160; challenge, especially in the peculiar environment that is the Black Sea. The retrieval of chlorophyll a (Chla) from fluorescence (Fluo) profiles recorded by biogeochemical-Argo (BGC-Argo) floats is not trivial in the Black Sea, due to the very high content of colored dissolved organic matter (CDOM) which contributes to the fluorescence signal and produces an apparent increase of the Chla concentration with depth.Here, we revised Fluo correction protocols for the Black Sea context using co-located in-situ high-performance liquid chromatography (HPLC) and BGC-Argo measurements. The processed set of Chla data (2014&#8211;2019) is then used to provide a systematic description of the seasonal DCM dynamics in the Black Sea and to explore different hypotheses concerning the mechanisms underlying its development.Our results show that the corrections applied to the Chla profiles are consistent with HPLC data. In the Black Sea, the DCM begins to form in March, throughout the basin, at a density level set by the previous winter mixed layer. During a first phase (April-May), the DCM remains attached to this particular layer. The spatial homogeneity of this feature suggests a hysteresis mechanism, i.e., that the DCM structure locally influences environmental conditions rather than adapting instantaneously to external factors.In a second phase (July-September), the DCM migrates upward, where there is higher irradiance, which suggests the interplay of biotic factors. Overall, the DCM concentrates around 45 to 65% of the total chlorophyll content within a 10 m layer centered around a depth of 30 to 40 m, which stresses the importance of considering DCM dynamics when evaluating phytoplankton productivity at basin scale.

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MARINE FORECAST FOR THE EASTERNMOST PART OF THE BLACK SEA

10.32008/geolinks2021/b1/v3/50 ◽

2021 ◽

Author(s):

Demuri Demetrashvili ◽

Vepkhia Kukhalashvili ◽

Diana Kvaratskhelia ◽

Aleksandre Surmava

Keyword(s):

Black Sea ◽

Splitting Method ◽

Equation System ◽

Water Area ◽

Regional Model ◽

Scale Model ◽

The Black Sea ◽

Marine Hydrophysical Institute ◽

Basin Scale ◽

Short Term Forecasting

Modelling and forecasting of dynamic processes and distribution of various substances of anthropogenic and natural origin in coastal and shelf zones of the seas and oceans are of great interest due to the high anthropogenic load of these zones. The aim of this paper is to present some examples of modelling and short-term forecasting of dynamic fields – the current, temperature and salinity in the easternmost Black Sea covering Georgian sector of the Black Sea and adjacent water area using a high-resolution regional model of the Black Sea dynamics. The z-level regional model is based on a full system of ocean hydro-thermodynamics equations and is nested in the basin-scale model of the Black Sea dynamics of Marine Hydrophysical Institute (Sevastopol). To solve the model equation system, a numerical algorithm based on the splitting method is used. Calculations show that circulation processes in the easternmost water area of the Black Sea are characterized by a permanent alternation of different circulation modes with the formation of mesoscale and submesoscale eddies throughout the year, which significantly affect the formation of thermohaline fields; atmospheric wind forcing substantially determines not only the peculiarities of the sea surface horizontal circulation, also the vertical structure of the current field.

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Dynamics of the deep chlorophyll maximum in the Black Sea as depicted by BGC-Argo floats

Biogeosciences ◽

10.5194/bg-18-755-2021 ◽

2021 ◽

Vol 18 (2) ◽

pp. 755-774

Author(s):

Florian Ricour ◽

Arthur Capet ◽

Fabrizio D'Ortenzio ◽

Bruno Delille ◽

Marilaure Grégoire

Keyword(s):

Black Sea ◽

Global Ocean ◽

The Black Sea ◽

Second Phase ◽

Deep Chlorophyll Maximum ◽

Phytoplankton Productivity ◽

Chl A ◽

Argo Floats ◽

Chlorophyll Maximum ◽

Basin Scale

Abstract. The deep chlorophyll maximum (DCM) is a well-known feature of the global ocean. However, its description and the study of its formation are a challenge, especially in the peculiar environment that is the Black Sea. The retrieval of chlorophyll a (chl a) from fluorescence (Fluo) profiles recorded by Biogeochemical Argo (BGC-Argo) floats is not trivial in the Black Sea, due to the very high content of coloured dissolved organic matter (CDOM) which contributes to the fluorescence signal and produces an apparent increase in the chl a concentration with depth. Here, we revised Fluo correction protocols for the Black Sea context using co-located in situ high-performance liquid chromatography (HPLC) and BGC-Argo measurements. The processed set of chl a data (2014–2019) is then used to provide a systematic description of the seasonal DCM dynamics in the Black Sea and to explore different hypotheses concerning the mechanisms underlying its development. Our results show that the corrections applied to the chl a profiles are consistent with HPLC data. In the Black Sea, the DCM begins to form in March, throughout the basin, at a density level set by the previous winter mixed layer. During a first phase (April–May), the DCM remains attached to this particular layer. The spatial homogeneity of this feature suggests a hysteresis mechanism, i.e. that the DCM structure locally influences environmental conditions rather than adapting instantaneously to external factors. In a second phase (July–September), the DCM migrates upward, where there is higher irradiance, which suggests the interplay of biotic factors. Overall, the DCM concentrates around 45 % to 65 % of the total chlorophyll content within a 10 m layer centred around a depth of 30 to 40 m, which stresses the importance of considering DCM dynamics when evaluating phytoplankton productivity at basin scale.

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Effects of mesoscale eddies on behavior of an oil spill resulting from an accidental deepwater blowout in the Black Sea: an assessment of the environmental impacts

PeerJ ◽

10.7717/peerj.5448 ◽

2018 ◽

Vol 6 ◽

pp. e5448

Author(s):

Konstantin A. Korotenko

Keyword(s):

Black Sea ◽

Oil Spill ◽

Marine Environment ◽

Ocean Circulation ◽

Coupled Model ◽

Circulation Model ◽

The Black Sea ◽

Basin Scale ◽

Near Shore ◽

Oil Source

Because of the environmental sensitivity of the Black Sea, as a semi-enclosed sea, any subsea oil spill can cause destructive impacts on the marine environment and beaches. Employing numerical modeling as a prediction tool is one of the most efficient methods to understand oil spill behavior under various environmental forces. In this regard, a coupled circulation/deepsea oil spill model has been applied to the Black Sea to address the behavior of the oil plume resulting from a representative hypothetical deepwater blowout. With climatological forcing, the hydrodynamic module based on DieCAST ocean circulation model realistically reproduces seasonally-varying circulation from basin-scale dominant structures to meso- and sub-mesoscale elements. The oil spill model utilizes pre-calculated DieCAST thermo-hydrodynamic fields and uses a Lagrangian tracking algorithm for predicting the displacement of a large number of seeded oil droplets, the sum of which forms the rising oil plume resulting from a deepwater blowout. Basic processes affecting the transport, dispersal of oil and its fate in the water column are included in the coupled model. A hypothetical oil source was set at the bottom, at the northwestern edge of the Shatsky Ridge in the area east of the Crimea Peninsula where the oil exploration/development is likely to be planned. Goals of the study are to elucidate the behavior of the subsea oil plume and assess scales of contamination of marine environment and coastlines resulting from potential blowouts. The two 20-day scenarios with the oil released by a hypothetical blowout were examined to reveal combined effects of the basin-scale current, near-shore eddies, and winds on the behavior of the rising oil plume and its spreading on the surface. Special attention is paid to the Caucasian near-shore anticyclonic eddy which is able to trap surfacing oil, detain it and deliver it to shores. The length of contaminated coastlines of vulnerable Crimean and Caucasian coasts are assessed along with amounts of oil beached and deposited.

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First record of Pseudodiaptomus marinus (Copepoda: Calanoida: Pseudodiaptomidae) in the Black Sea (Sevastopol Bay)

Marine Biological Journal ◽

10.21072/mbj.2016.01.4.11 ◽

2016 ◽

Vol 1 (4) ◽

pp. 78-80 ◽

Cited By ~ 4

Author(s):

O. A. Garbazey ◽

E. V. Popova ◽

A. D. Gubanova ◽

D. A. Altukhov

Keyword(s):

Black Sea ◽

Structural Changes ◽

The Black Sea ◽

Mnemiopsis Leidyi ◽

Northwestern Pacific ◽

Basin Scale ◽

Wide Range ◽

Sevastopol Bay ◽

Pseudodiaptomus Marinus

Pseudodiaptomus marinus was initially discovered at the end of September 2016 in a sample taken during a long-term plankton survey of Sevastopol Bay started in 2002. We found 6 females and 12 copepodites (I-V stages) of P. marinus at the center of Sevastopol Bay (St. 3) on September 22. At the mouth of Bay (St. 2) the species was not found. Both females and copepodite stages I-V of P. marinus were found at the both stations on November 11. Abundance of P. marinus increased to 1236 individuals in sample (1373 ind/m3) at the center of the bay. Moreover, two individuals of P. marinus nauplii identified by Sazhina, were found in this sample. At the mouth of the bay abundance of the invasive species reached 103 individuals in sample (103 ind/m3). It is considered to be native to the Northwestern Pacific Ocean, but now species is widespread across the world. Brilinski described in details its distribution in the World's oceans. Recently P. marinus has been found in the Atlantic Ocean in the North Sea and in the Mediterranean Sea. P. marinus is a typical estuarine coastal copepod, living in shallow eutrophic inshore waters. It is tolerant to a wide range of salinity (2.5-35 ptt) and temperature (5-28 ºC) and has the highest invasive potential. Thus species is adapted to relatively low salinities and low winter temperatures of the Black Sea. Copepodite stages at both stations indicate the existence of reproducing populations. Thus, very likely P. marinus is the new established species in coastal area of the Black Sea. As other recent pelagic invaders – the copepods Acartia tonsa Dana 1849, Oithona davisae Ferrari F. D. & Orsi 1984; ctenophores Mnemiopsis leidyi A. Agassiz, 1865 and Beroe ovata Bruguiere, 1789 - P. marinus was most probably brought into Sevastopol Bay in the ballast water of ships. Long-term studies at basin scale are needed to estimate the structural changes in the Black Sea zooplankton community.

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Modeling long-term changes of the Black Sea ecosystem characteristics

Ocean Science Discussions ◽

10.5194/osd-9-2039-2012 ◽

2012 ◽

Vol 9 (3) ◽

pp. 2039-2080 ◽

Cited By ~ 1

Author(s):

V. L. Dorofeyev ◽

T. Oguz ◽

L. I. Sukhikh ◽

V. V. Knysh ◽

A. I. Kubryakov ◽

...

Keyword(s):

Black Sea ◽

Inorganic Nitrogen ◽

The Black Sea ◽

Mnemiopsis Leidyi ◽

Biogeochemical Model ◽

Food Web Structure ◽

Decadal Scale ◽

Basin Scale ◽

Long Term Changes

Abstract. A three dimensional coupled physical-biological model is provided for the Black Sea to investigate its long-term changes under the synergistic impacts of eutrophication, climatic changes and population outbreak of the gelatinous invader Mnemiopsis leidyi. The model circulation field is simulated using the high frequency ERA40 atmospheric forcing as well as assimilation of the available hydrographic and altimeter sea level anomaly data for the 30 yr period of 1971–2001. The circulation dynamics are shown to resolve well the different temporal and spatial scales from mesoscale to sub-basin scale and from seasonal peaks to decadal scale trend-like changes. The biogeochemical model includes the main vertical biological and chemical interactions and processes up to the anoxic interface zone. Its food web structure is represented by two phytoplankton and zooplankton size groups, bacterioplankton, gelatinous carnivores Mnemiopsis and Aurelia, opportunistic species Noctiluca scientillans. The nitrogen cycling is accommodated by the particulate and dissolved organic nitrogen compartments and the dissolved inorganic nitrogen in the forms of ammonium, nitrite and nitrate. The ecosystem model is able to simulate successfully main observed features and trends of the intense eutrophication phase (from the early 1970s to the early 1990s), but points to its modification to simulate better the ecosystem conditions of the post-eutrophication phase.

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Operative forecast of hydrophysical fields in the Georgian Black Sea coastal zone within the ECOOP

Ocean Science Discussions ◽

10.5194/osd-8-397-2011 ◽

2011 ◽

Vol 8 (1) ◽

pp. 397-433 ◽

Cited By ~ 1

Author(s):

A. A. Kordzadze ◽

D. I. Demetrashvili

Keyword(s):

High Resolution ◽

Black Sea ◽

Surface Wind ◽

Scale Model ◽

The Black Sea ◽

Time Step ◽

Regional Area ◽

Study Results ◽

Basin Scale ◽

Forecasting System

Abstract. One of the part of the Black Sea Nowcasting/Forecasting System is the regional forecasting system for the Easternmost part of the Black Sea (including the Georgian water area), which have been developed within the context of the EU International projects ARENA and ECOOP. A core of the regional system is a high-resolution baroclinic regional model of the Black Sea dynamics developed at M. Nodia Institute of Geophysics (RM-IG). This model is nested in the basin-scale model (BSM) of Marine Hydrophysical Institute (MHI, Sevastopol/Ukraine). The regional area is limited to the Caucasian and Turkish coastal lines and the western liquid boundary coinciding with a meridian 39.36° E. Since June 2010 we regularly compute 3 days' forecasts of current, temperature and salinity for the Easternmost part of the Black Sea with 1 km spacing. In this study results of two forecasts are presented. The first forecast corresponds to Summer season and covers the prognostic interval from 00:00 h, 6 August to 00:00 h, 9 August 2010. The second one corresponds to Autumn season and covers the prognostic interval from 00:00 h, 26 October to 00:00 h, 29 October 2010. Data needed for the forecasts – the 3-D initial and prognostic hydrophysical fields, also 2-D prognostic meteorological fields at the sea surface, wind stress, heat fluxes, evaporation and precipitation rates for the our regional area are placing on the MHI server every day and we are available to use these data operatively. Prognostic hydrophysical fields are results of forecast by BSM of MHI and 2-D meteorological boundary fields represent results of forecast by regional atmospheric model ALADIN. All these fields are given on the grid of BSM with 5 km spacing and with one-hour time step frequency for the integration period. The analysis of predicted fields shows that to use the model with high resolution is very important factor for identification of nearshore eddies of small sizes. It should be noted very different character of regional circulation in summer and autumn seasons in the Easternmost part of the Black Sea.

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