scholarly journals Snapshot observation of physical structure and stratification in deep-water of the South Caspian Sea (western part)

2009 ◽  
Vol 6 (3) ◽  
pp. 2555-2578
Author(s):  
P. Ghaffari ◽  
H. A. Lahijani ◽  
J. Azizpour
Keyword(s):  
Continental Shelf ◽  
Mixed Layer ◽  
Caspian Sea ◽  
Static Stability ◽  
Physical Structure ◽  
Water Masses ◽  
Physical Parameters ◽  
Surface Mixed Layer ◽  
The Caspian Sea ◽  
Southwestern Part

Abstract. In this article, we describe physical parameters structures and different water masses using CTD measurements in southwestern part of the Caspian Sea (CS) in adjacent to Anzali Port (AP). CTD profilings were conducted along a transect perpendicular to the coastline over 13 stations from the coast down to 720 m in winter 2008. According to the results the continental shelf waters are located in surface mixed layer. Surface mixed layer extends itself down to almost 100 m in outer areas of the continental shelf with a weak seasonal thermocline layer between 80 to 140 m. Freshwaters inflow of local rivers is clearly seen outside continental shelf at the surface layers. Investigating the dissolved oxygen reveals that winter convection is traceable down to 500 m in the lateral waters over the shelf break. Among the deeper stations that are located in continental rise and abyssal plain, 350 m seems to be threshold for penetration of seasonal changes; therefore deeper waters tend to be impermeable against seasonal variances. Despite to the small variations, stability is positive in most region of the study area and temperature plays an important role in static stability and in triggering the lateral mixing. In view of both temperature-salinity and temperature-oxygen distributions in the southwestern part of the CS, three different water masses are separable in cold phase. Snapshot observation of physical properties in the early winter 2008, to some extent revealed that a mixing was triggered at least in the lateral waters of the study area.

scholarly journals Snapshot observation of the physical structure and stratification in deep-water of the South Caspian Sea (western part)

Ocean Science ◽  
2010 ◽  
Vol 6 (4) ◽  
pp. 877-885 ◽  
Author(s):  
P. Ghaffari ◽  
H. A. Lahijani ◽  
J. Azizpour
Keyword(s):  
Continental Shelf ◽  
Mixed Layer ◽  
Caspian Sea ◽  
Static Stability ◽  
Physical Structure ◽  
Water Masses ◽  
Physical Parameters ◽  
Surface Mixed Layer ◽  
The Caspian Sea ◽  
Southwestern Part

Abstract. The physical parameters structures and different water masses using CTD measurements in southwestern part of the Caspian Sea (CS) adjacent to Anzali Port (AP) are investigated. CTD profiles were conducted along a transect perpendicular to the coastline on 13 stations from the coast down to 720 m on 22 January 2008. According to the results the continental shelf waters are located in the surface mixed layer. The surface mixed layer extends itself down to almost 100 m in outer areas of the continental shelf with a weak seasonal thermocline layer between 80 to 140 m Freshwaters inflow of local rivers is clearly seen outside the continental shelf at the surface layers. Investigating the dissolved oxygen reveals that winter convection is traceable down to 500 m in the lateral waters over the shelf break. Among the deeper stations that are located in continental rise and abyssal plain, 300 m seems to be a threshold for penetration of seasonal changes; therefore deeper waters tend to be impermeable against seasonal variances. Despite the small variations, stability is positive in the study area and temperature plays an important role in static stability and in triggering the lateral mixing. In view of both temperature-salinity and temperature-oxygen distributions in the southwestern part of the CS, two different water masses are separable in cold phase. Snapshot observations of physical properties in the early winter 2008, to some extent revealed that a mixing was triggered at least in the lateral waters of the study area.

scholarly journals Study of the Effective Factors on Shelf Currents in the Southern Caspian Sea

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Maryam ShieaAli
Keyword(s):  
Caspian Sea ◽  
Low Frequency ◽  
Coastal Current ◽  
Surface Currents ◽  
Measured Temperature ◽  
The Caspian Sea ◽  
The West ◽  
Southwestern Part ◽  
Significant Difference ◽  
Weak Winds

The current and wind records and the physical parameter structures such as temperature and salinity in the southwestern part of the Caspian Sea adjacent to Anzali Port were investigated from November 2004 up to the end of January 2005. Results show that, despite the existence of relatively weak winds along the coast in the area, the measurements indicate strong long shore currents. However, when heavy wind tension is observed in the area, then strong currents are also present, which - from the perspective of direction – also have good coordination with the wind. The direction of dominated currents was parallel to the coast from the west to the east. In most cases, the flow rate was identical from the surface to the seabed, and in this condition - because the values of the measured temperature points were almost identical-barotropic currents were present. However, in the autumn at some region, a significant difference was observed between the surface currents and subsurface currents due to temperature differences that affected the density and caused the creation of barclinic currents. Due to the high velocity of currents compared to wind velocity, and the intense slope of the coast and low-frequency movements in the area, we can hypothesize the existence of motions such as Kelvin waves and conclude that the effect of the wind compared to the other factors of the coastal current in the area was weaker.

scholarly journals Comparison of spawning patterns of the Brazilian sardine (Sardinella brasiliensis) and anchoita (Engrautis anchoita) in Ubatuba region, southern Brazil during 1985 through 1988

1992 ◽  
Vol 40 (1-2) ◽  
pp. 101-115 ◽  
Author(s):  
Yasunobu Matsuura ◽  
Henry L. Spach ◽  
Mário Katsuragawa
Keyword(s):  
Mixed Layer ◽  
Cold Water ◽  
Coastal Region ◽  
Bottom Layer ◽  
Water Masses ◽  
Late Spring ◽  
Surface Mixed Layer ◽  
Southern Brazil ◽  
South Atlantic Central Water ◽  
Spawning Time

The Brazilian sardine (Sardinella brasiliensis) and anchoita (Engrautis anchoita) inhabit the southeastern Brazilian Bight. The former spawns at night (21:00-03:00) in coastal region during late-spring and summer, meanwhile, the latter spawns all year-around, mainly in coastal region during summer and in neritic region during winter. The spawning time of E. anchoita was observed all day long, but more intensively at night. During summer there occurs a strong vertical stratification of water masses. The spawning of S. brasiliensis occurs in surface mixed layer, while that of E. anchoita occurs beneath the thermocline inside the cool South Atlantic Central Water which occupies the bottom layer during late spring and summer. However, the sardine and anchovy egss and larvae were found inside both the upper tropical and lower cold water masses, but predominantly above thermocline in this region

scholarly journals Study of the Effective Factors on Shelf Currents in the Southern Caspian Sea

2019 ◽  
Vol 1 (1) ◽  
Author(s):  
Maryam ShieaAli
Keyword(s):  
Caspian Sea ◽  
Low Frequency ◽  
Coastal Current ◽  
Surface Currents ◽  
Measured Temperature ◽  
The Caspian Sea ◽  
The West ◽  
Southwestern Part ◽  
Significant Difference ◽  
Weak Winds

The current and wind records and the physical parameter structures such as temperature and salinity in the southwestern part of the Caspian Sea adjacent to Anzali Port were investigated from November 2004 up to the end of January 2005. Results show that, despite the existence of relatively weak winds along the coast in the area, the measurements indicate strong long shore currents. However, when heavy wind tension is observed in the area, then strong currents are also present, which - from the perspective of direction – also have good coordination with the wind. The direction of dominated currents was parallel to the coast from the west to the east. In most cases, the flow rate was identical from the surface to the seabed, and in this condition - because the values of the measured temperature points were almost identical-barotropic currents were present. However, in the autumn at some region, a significant difference was observed between the surface currents and subsurface currents due to temperature differences that affected the density and caused the creation of barclinic currents. Due to the high velocity of currents compared to wind velocity, and the intense slope of the coast and low-frequency movements in the area, we can hypothesize the existence of motions such as Kelvin waves and conclude that the effect of the wind compared to the other factors of the coastal current in the area was weaker.

scholarly journals Hydrological factors of formation of oxygen regime of inland seas

2018 ◽  
pp. 90-97
Author(s):  
N. Berlinsky
Keyword(s):  
Gas Exchange ◽  
Black Sea ◽  
Caspian Sea ◽  
Regime Shift ◽  
Static Stability ◽  
The Black Sea ◽  
Northwestern Part ◽  
The Caspian Sea ◽  
Oxygen Regime ◽  
Deep Layers

Introduction. The regularities of the formation and dynamics of the oxygen regime in inland seas - the Black Sea and Caspian, under the influence of natural and anthropogenic factors are estimated. Purpose. One of the features of the Black Sea is the absence of dissolved oxygen in the water below 200 meters depth. A comparison is made between the hydrological conditions of the Black Sea and the Caspian, where the depths are also quite large, but the intensity of vertical exchange is different. In addition, it is necessary to distinguish the reasons for the formation of oxygen deficient in the seas. They can be natural and human-made origin as well. The paper presents an analysis of the cause-and-effect patterns of the development of pelagial hypoxia as the examples of the Caspian and the Black Sea. Methods. The work is the review of the problem literature that allows an assessment of the cur-rent state of gas exchange of pelagic and abyssal marine basins. Results. Three main formation factors of the features of the hydrological structure and processes responsible for the intensity of gas exchange in the pelagic zone are identified. So, in the Black Sea, saline waters come with the Lower Bosporus Current and flow down the slope, filling the deep layers of the Black Sea basin, forming a stable vertical stratification density, that limiting vertical gas exchange. The second factor is contributing to oxygen saturation of the lower layers during the process of winter vertical circulation that is mainly expressed in the northwestern part. The third factor is the regime shift of 1976-1978 in the Black Sea as a decrease of the winter temperature and salinity in the surface layer that led to increasing of static stability. According to actively developed convection processes, covering the entire body of the Caspian Sea, in contrast to the Black Sea, there is an intensive exchange between the upper and the deep layers and the intensity of convection depends on the temperature regime of the year. In the Caspian Sea, the regime shift of 1976-1978 led to a twofold increase in the static stability of water below 100 m, the almost complete cessation of the ventilation of the deep waters of the (the process the slope cascading) and the extreme decrease in the concentrations of dissolved oxygen. Conclusion. In the Black Sea, the formation of a stable of the density vertical stratification is due to the intrusion of saline dense waters of the Lower Bosporus Current, and the winter vertical circulation is expressed only in the northwestern part of the sea, which generally limits vertical gas exchange with the deep water. In the Caspian Sea, convective mixing plays a main role in the for-mation of the hydrological structure of water and the ventilation of the bottom layers. In cold winters in the northern Caspian, strong cooling, as well as salinity during ice formation, creates the conditions for the formation of waters with a density that allows them to flow down the slopes of  the bottom along isopycnic surfaces and aerating the deep layers of the sea.

THE NUMBER AND QUALITATIVE CHARACTERISTICS OF FRY FISH IN SHALLOW COASTAL WATERS OF THE VOLGA IN THE SUMMER-AUTUMN PERIOD OF 2012

2017 ◽  
pp. 65-73
Author(s):  
Edward Vladimirovich Nikitin
Keyword(s):  
Fish Species ◽  
Coastal Waters ◽  
Caspian Sea ◽  
The Caspian Sea ◽  
Volga River ◽  
Commercial Fish ◽  
Autumn Period ◽  
Fish Juveniles ◽  
Qualitative Characteristics ◽  
Shallow Coastal Waters

Shallow coastal waters of the Volga river is a flooded feeding area for fish juveniles of nonmigratory fish species. There takes place annual downstream migration of fluvial anadromous fish species from spawning grounds of the Volga river to the Northern Caspian Sea. The most important factors determining the number and qualitative characteristics of fry fishes are the level of the Caspian Sea (currently having a tendency to the lowering), hydrological and thermal regimes of the Volga river. Researches were carried out in definite periods of time. In the summer-autumn period of 2012 fry fishes were presented by 19 species (13 of them were commercial species), which belonged to 9 families. The article gives data on all the commercial fish species. In the first decade of July the maximum number of fry fish was registered in the western part of the Volga outfall offshore - in box 247 (19.86 mln specimens/km2), in the eastern part - in box 142 (20.4 mln specimens/km2). The most populous were roach, red-eye, silver bream and bream; size-weight characteristics were better in the areas remoted from the Volga delta. In the third decade of July the quantitative indicators of fry fish on these areas decreased, size-weight characteristics greatly increased. In the second decade of October in the western part of the seaside there were registered increased pre-wintering concentrations of fish juveniles, their qualitative indicators increased, which is evidence to favorable feeding conditions in 2012.

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