scholarly journals The short timescale variability of the oxygen inventory in the NE Black Sea slope water

Ocean Science ◽  
2018 ◽  
Vol 14 (6) ◽  
pp. 1567-1579
Author(s):  
Alexander G. Ostrovskii ◽  
Andrey G. Zatsepin ◽  
Vladimir A. Solovyev ◽  
Dmitry M. Soloviev
Keyword(s):  
Black Sea ◽  
Bottom Layer ◽  
Temporal Variations ◽  
The Black Sea ◽  
Low Oxygen ◽  
Oxygen Penetration ◽  
Direct Observations ◽  
Faunal Abundance ◽  
Vertical Displacements ◽  
Oxygenated Water

Abstract. Warm winters have recently become common over the Black Sea, leading to the risk of shoaling oxygen penetration. The insufficient supply of oxygen to the near-bottom layer may result in a decrease in faunal abundance. However, there is a lack of data on the temporal variations in oxygen throughout the water column over short timescales of hours to weeks. In this paper, new observations over the upper part of the NE Black Sea continental slope are presented. Regular, frequent measurements were performed using a moored profiler from January to early March 2016. The profiling allowed for direct observations of the temperature in the cold intermediate layer (CIL), pycnocline structure, current velocity, and oxygen stratification and in particular, the depths of hypoxia onset. The average local oxygen inventory below a depth of 30 m was 24.9 mol m−2. Relatively high/low oxygen inventory cases were related to the thin/thick main pycnocline, which was associated with the onshore/offshore location of the Black Sea Rim Current. The pycnocline hindered the vertical transport of oxygenated water to the CIL. The vertical displacements of the hypoxia onset depth ranged from 97 to 170 m, while the shelf edge depth in this region usually ranged from 90 to 100 m. Intermittently, the hypoxia boundary depth fluctuated on two timescales: ∼17 h due to inertial oscillations and 3–7 days due to current meanders and eddies.

scholarly journals The temporal variability of oxygen inventory in the NE Black Sea slope water

2018 ◽  
Author(s):  
Alexander G. Ostrovskii ◽  
Andrey G. Zatsepin ◽  
Vladimir A. Solovyev
Keyword(s):  
Black Sea ◽  
Oxygen Sensor ◽  
Temporal Dynamics ◽  
Shelf Break ◽  
The Black Sea ◽  
Low Oxygen ◽  
Water Column Stratification ◽  
Direct Observations ◽  
Vertical Displacements ◽  
Oxygenated Water

Abstract. The time series of vertical profiles of hydrophysical parameters and dissolved oxygen are critical for identifying trends in water column stratification, mixing, and ventilation in the Black Sea. Due to global warming, warm winters have recently become common over the Black Sea, and the temperature in the cold intermediate layer (CIL) is increasing. Regular measurements that are as frequent as every 2 h were performed using a moored profiler near the shelf break at a depth of 220 m in the northeastern Black Sea from January to early March 2016 to assess the temporal dynamics of the oxygen inventory over the upper part of the continental slope on timescales from hours to months. The moored profiler was equipped with a sensor suite that included the CTD 52-MP CTD with the fast oxygen sensor SBE43F and the acoustic Doppler current meter Nortek Aquadopp 2 MHz, which allowed for direct observations of the CIL temperature, the pycnocline structure, the current velocity and the oxygen stratification, in particular, the depths of the hypoxia onset. The average oxygen inventory below a depth of 30 m was 24.9 mol m−2. Relatively high/low oxygen inventory cases were related to the thin/thick main pycnocline that was associated with the inshore/offshore location of the Black Sea Rim Current. The pycnocline hindered the vertical transport of oxygenated water to the CIL. The new CIL emerged by horizontal advection above the pycnocline only at the end of the observational survey. The vertical displacements of the hypoxia onset depth ranged from 97–170 m, while the shelf edge depth in this region usually ranges from 90–100 m. Intermittently, the hypoxia boundary depth fluctuated on two-time scales: ~ 17 h due to the inertial oscillations and approximately 5 days due to the current meanders and eddies. Further efforts are urgently needed for monitoring the rise of hypoxia onset depth above the shelf break in the Black Sea.

scholarly journals On the possible presence of oxygen in the upper sediment layer of the hydrogen sulfide zone in the Black Sea

2019 ◽  
Vol 59 (1) ◽  
pp. 166-169
Author(s):  
P. A. Stunzhas ◽  
M. B. Gulin ◽  
A. G. Zatsepin ◽  
E. A. Ivanova
Keyword(s):  
Black Sea ◽  
Benthic Fauna ◽  
Water Layer ◽  
Bottom Layer ◽  
The Black Sea ◽  
Depth Range ◽  
Sediment Layer ◽  
Bottom Water Layer ◽  
Long Time ◽  
Eukaryotic Organisms

In the northeastern Black Sea the search was performed for living eukaryotic organisms (micro- and meiobenthos) in hypoxic and anoxic conditions as well as measurement of O2 in the bottom water layer and in the upper layer of sediments. The results have shown the presence of a deep maximum abundance of zoobenthos in a depth range of 215–244 m. This aggregation of benthic fauna occupies a layer of 30 m along the vertical. In general, the proportion of active meiobenthos was no greater than 1.5% of the total number of organisms recorded from the sample.The presence of aerobic benthos near the upper boundary of the H2S zone can be explained by: sliding down of sediments from a higher depth; quasi-periodic O2 supply due to fluctuations in the position of the isopycna and/or sinking of waters downslope in the bottom Ekman layer. Also, in the case of physical entry of oxygen into the bottom layer, it can remain for a relatively long time in the upper part of the H2S zone due to the lack of deep Mn+2 flux and reaction with it.

Biogeochemical controls on the Black Sea oxygen dynamics : relevant diagnostics, key processes and adequacy of the monitoring infrastructure.

2020 ◽  
Author(s):  
Arthur Capet ◽  
vandenbulcke Luc ◽  
Grégoire Marilaure
Keyword(s):  
Black Sea ◽  
3D Models ◽  
The Black Sea ◽  
Biogeochemical Model ◽  
Model Parameters ◽  
Biogeochemical Processes ◽  
Low Oxygen ◽  
Future Evolution ◽  
Basin Scale ◽  
Set Up

<p>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. </p><p>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.</p><p>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<br>photic zone. Organic matter (OM) is respired over a depth determined by its composition and<br>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.</p><p>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. </p><p>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. </p><p>[1] Capet A et al., 2016, Biogeoscience, 13:1287-1297<br>[2] Oschlies A et al., 2018, Nature Geosci, 11(7):467–473</p>

COASTAL EROSION IN THE GULF OF KALAMITA AS A RESULT OF LONG-TERM ANTHROPOGENIC INFLUENCE

2017 ◽  
Author(s):  
Yuri Goryachkin ◽  
Yuri Goryachkin
Keyword(s):  
Black Sea ◽  
Anthropogenic Impacts ◽  
Sandy Beaches ◽  
The Black Sea ◽  
Storm Activity ◽  
Direct Observations ◽  
The Crimea ◽  
Near Shore ◽  
Annual Scale

The Gulf of Kalamita is located in the Black Sea off the west coast of the Crimea and is known to be a major recreational area. However, in the last 30 years, its famous sandy beaches have drastically degraded. Degradation of sandy beaches was expressed in erosion of the coastal line (30-70 m) and reduction of the total area of beaches; disappearance of sand in a number of ar-eas in the near-shore zone and openings of marl; sharp increase of fragments of limestone in the composition of beaches. In the last 60 years, the level of the Black Sea has risen by 14 cm. Only this factor, as the calculations show, has caused about 15 mln m3 deficiency of deposits. Accord-ing to direct observations, shoreline response to changes in the sea level at the inter-annual scale changes comproses 0,3 m per 1 cm. Climate changes in trajectories of passing cyclones have resulted in a 2-3 times increase in storm activity over the past 30 years. The contribution of natural factors into the shoreline changes do not exceed 10-15% according to our estimates. The main contribution is related to the background and point anthropogenic impacts. The first group includes overall reduction of sediment in the sea due to construction of reservoirs, cliffs closing with concrete embankments, reducing populations of benthic mollusks for various rea-sons, etc. The second group includes construction of hydraulic structures which do not address lithodynamics peculiarities in particular stretches of coastline.

Hydrometeorological Conditions in the Southern Part of the Kerch Strait and the Pre-Strait Zone of the Black Sea as a Potential Area for Industrial Shellfish Cultivation

2020 ◽  
pp. 112-117
Author(s):  
Natalya A. Sytnik
Keyword(s):  
Black Sea ◽  
Bottom Layer ◽  
Water Area ◽  
The Black Sea ◽  
Frequent Change ◽  
Trophic Conditions ◽  
Kerch Strait ◽  
Sea Currents ◽  
Summer Minimum ◽  
Hydrometeorological Conditions

Considered materials on the hydrometeorological conditions of the Kerch Strait and the Black Sea. The data on the wind regime in the study areas are presented. The materials on currents and water exchange in the southern part of the Kerch Strait and the Black Sea waters are presented. The average monthly, annual, minimum and maximum values of air temperature at the coastal hydrometeorological stations are analyzed. In the seasonal course of salinity, in contrast to the regularities in the sea zone (in the surface and bottom layers), there is no summer minimum in the bottom layer of the strait. This indicates the development of coastal upwellings in the Black Sea in the summer, which facilitates the penetration of the Black Sea waters into the strait in the bottom layer. The oxygen saturation of the waters in the strait (both in the surface and in the bottom layers) is higher than in the sea area. This indicates a more intensive course of production processes. The stable Azov currents are most favorable for the plantations located in the strait near the Crimean coast during the collection of larvae on the collector and for the improvement of trophic conditions in the plantation areas. For the purification of coastal waters from suspended matter, the Black Sea currents are preferred. The frequent change of the Azov and Black Sea currents creates favorable conditions for the effective operation of mariculture farms. On the basis of the studies carried out, conclusions were drawn about the possibility of industrial cultivation of mollusks in the water area of the Kerch Strait and the Black Sea.

Tinogullmia lukyanovae sp. nov.—a monothalamous, organic-walled foraminiferan from the coastal Black Sea

2006 ◽  
Vol 86 (1) ◽  
pp. 43-49 ◽  
Author(s):  
Andrew J. Gooday ◽  
Oksana V. Anikeeva ◽  
Nelly G. Sergeeva
Keyword(s):  
New Species ◽  
Black Sea ◽  
Coastal Waters ◽  
Bottom Water ◽  
The Black Sea ◽  
The Caucasus ◽  
The World ◽  
Oxygenated Water ◽  
Deep Site

Recent studies indicate that monothalamous (single-chambered) foraminifera are an important component of meiobenthic communities in the brackish, coastal waters of the Black Sea. The dominant taxa include Psammophaga and Vellaria, both of which are common in estuarine settings in other parts of the world. Here, we describe Tinogullmia lukyanovae sp. nov. from the Crimean and Caucasus regions of the Black Sea. The new species is several hundreds of microns in size. It is characterized by a more or less symmetrical, spindle-shaped to cylindrical, organic-walled test with two terminal apertural structures, usually in the form of rounded or more elongate, nipple-like projections. The protoplasm is finely granular and a nucleus is not visible. The new species typically occurs in well-oxygenated water at depths of a few tens of metres or less. A specimen from a 250-m deep site off the Caucasus coast, tentatively assigned to T. lukyanovae sp. nov., is of particular interest because it occurs at a depth where the bottom water is anoxic and sulphidic.

scholarly journals Internal waves of mode 2 in the Black Sea

2019 ◽  
Vol 488 (5) ◽  
pp. 555-559
Author(s):  
A. N. Serebryany ◽  
E. E. Khimchenko
Keyword(s):  
Water Column ◽  
Internal Waves ◽  
Black Sea ◽  
Horizontal Component ◽  
The Black Sea ◽  
Short Period ◽  
Mode 2 ◽  
Vertical Displacements

The results of the first observations of mode 2 internal waves in the Black Sea are presented. The measurements were carried out on the Crimean shelf from the MGI platform in July 2011. In the period after the sweep, when measurements were taken, firstly mode 1 inertial internal waves were observed, and then mode 2 one. The oscillations of mode 2 were most pronounced in the vertical displacements of the water column, reaching amplitudes of 10 m. The features of mode 2 were also noted in fluctuations of the horizontal component of the currents. Along with the registration of mode 2 inertial internal waves, the appearance of short-period internal waves of mode 2 was also noted.

scholarly journals The energy spectrum of the current velocity in deep layers of the Black Sea

2019 ◽  
Vol 488 (5) ◽  
pp. 550-554
Author(s):  
A. A. Klyuvitkin ◽  
A. G. Ostrovskii ◽  
A. P. Lisitzin ◽  
S. K. Konovalov
Keyword(s):  
Energy Spectrum ◽  
Black Sea ◽  
Blue Shift ◽  
Bottom Layer ◽  
The Black Sea ◽  
Spectral Energy ◽  
Data Set ◽  
Deep Layers ◽  
Deep Current ◽  
First Time

In 2016-2017, for the first time, nearly year-long measurements of the current velocities were carried out below the thermocline at a depth of 100 m and at a depth of 1700 m that was about 100 m above the seabed by using the mooring station in the deep central part of the Black Sea. Analysis of the new data set allowed us to uncover the followings. In the near-bottom layer, the significant flow velocities were recorded, reaching a peak magnitude of 0.13 m/s. Near the frequency of 110-6 Hz, in the transition region of the energy spectrum, the spectral energy of the deep current was close to that observed in the same range in the subthermocline layer of the sea. In the range of balanced geostrophic motions, the energy spectrum had a slope of -2,8 that should be compared to a spectrum slope of -1,8 obtained for current below the thermocline. The regular strong horizontal currents were observed near the local inertial frequency fI. There was a blue shift of the inertial maximum up to 5% with respect to fI in the energy spectrum.

scholarly journals Decline of the Black Sea oxygen inventory

2016 ◽  
Vol 13 (4) ◽  
pp. 1287-1297 ◽  
Author(s):  
Arthur Capet ◽  
Emil V. Stanev ◽  
Jean-Marie Beckers ◽  
James W. Murray ◽  
Marilaure Grégoire
Keyword(s):  
Spatial Variability ◽  
Penetration Depth ◽  
Black Sea ◽  
The Black Sea ◽  
Nutrient Loads ◽  
Oxygen Penetration ◽  
Oxygen Penetration Depth ◽  
Atmospheric Warming ◽  
The Stability ◽  
Near Future

Abstract. We show that from 1955 to 2015, the inventory of oxygen in the Black Sea has decreased by 44 % and the basin-averaged oxygen penetration depth has decreased from 140 m in 1955 to 90 m in 2015, which is the shallowest annual value recorded during that period. The oxygenated Black Sea surface layer separates the world's largest reservoir of toxic hydrogen sulfide from the atmosphere. The threat of chemocline excursion events led to hot debates in the past decades arguing on the vertical stability of the Black Sea oxic/suboxic interface. In the 1970s and 1980s, when the Black Sea faced severe eutrophication, enhanced respiration rates reduced the thickness of the oxygenated layer. Re-increasing oxygen inventory in 1985–1995 supported arguments in favor of the stability of the oxic layer. Concomitant with a reduction of nutrient loads, it also supported the perception of a Black Sea recovering from eutrophication. More recently, atmospheric warming was shown to reduce the ventilation of the lower oxic layer by lowering cold intermediate layer (CIL) formation rates. The debate on the vertical migration of the oxic interface also addressed the natural spatial variability affecting Black Sea properties when expressed in terms of depth. Here we show that using isopycnal coordinates does not overcome the significant spatial variability of oxygen penetration depth. By considering this spatial variability, the analysis of a composite historical set of oxygen profiles evidenced a significant shoaling of the oxic layer, and showed that the transient "recovery" of the 1990s was mainly a result of increased CIL formation rates during that period. As both atmospheric warming and eutrophication are expected to increase in the near future, monitoring the dynamics of the Black Sea oxic layer is urgently required to assess the threat of further shoaling.

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