Thermohaline structure in the equatorial Indian Ocean during Monsoon-77

The hydrographic and BT data sets collected in the upper 200 m water column along three zonal transects (2°N, equator and 2°S) in the equatorial Indian Ocean (between 70oE and 90OE) made by USSR ships during the field observational programme of Monsoon-77 (end May/early June 1977) showed prominent eastward depression of thermocline in association with the surface easterly equatorial jet. In the central indian. Ocean, the mixed layer cooling and deepening rates were weak with the. Onset and sway of the summer monsoon over a two month period from end May 1977, but relatively significant changes were noticed in the salinity of the upper 200 m water column. In this region, on a synoptic scale a mild increase in SST is in accor4ance with the net surface heat gain during the last week of July 1977.

CONTROL OF POTENTIAL MUSSEL RECRUITMENT TAKING INTO ACCOUNT SOME ENVIRONMENTAL PARAMETERS IN SEVASTOPOL ESTUARINE ZONE

In 2020-2021, potential recruitment of the mussel Mytilus galloprovincialis was measured in Sevastopol estuarine waters with regard to temperature, salinity, and pH in three depth horizons 1–3, 7, and 11 m. Compared to the previous annual period in 2021, spring mussel recruitment at all depth horizons in-creased by an order of magnitude. This increase was preceded by a mild winter. Also in 2021, a decrease in salinity and an increase in the vertical variability of the thermohaline structure of water were observed. The obtained data may indirectly indicate the improvement of environmental conditions for mussel productivity increase in 2021. The necessity of improving the method of the control for mussel recruit-ment related to possible vertical migrations of its post-larvae is shown.

Double diffusion, shear instabilities, and heat impacts of a Pacific Summer Water intrusion in the Beaufort Sea

Pacific Summer Water eddies and intrusions transport heat and salt from boundary regions into the western Arctic basin. Here we examine concurrent effects of lateral stirring and vertical mixing using microstructure data collected within a Pacific Summer Water intrusion with a length scale of ∼20 km. This intrusion was characterized by complex thermohaline structure in which warm Pacific Summer Water interleaved in alternating layers of O(1 m) thickness with cooler water, due to lateral stirring and intrusive processes. Along interfaces between warm/salty and cold/fresh water masses, the density ratio was favorable to double-diffusive processes. The rate of dissipation of turbulent kinetic energy (ε) was elevated along the interleaving surfaces, with values up to 3×10−8 W kg−1 compared to background ε of less than 10−9 W kg−1. Based on the distribution of ε as a function of density ratio Rρ , we conclude that double-diffusive convection is largely responsible for the elevated ε observed over the survey. The lateral processes that created the layered thermohaline structure resulted in vertical thermohaline gradients susceptible to double-diffusive convection, resulting in upward vertical heat fluxes. Bulk vertical heat fluxes above the intrusion are estimated in the range of 0.2-1 W m−2, with the localized flux above the uppermost warm layer elevated to 2- 10 W m−2. Lateral fluxes are much larger, estimated between 1000-5000 W m−2, and set an overall decay rate for the intrusion of 1-5 years.

On the use of acoustic data to characterise the thermohaline stratification in a tropical ocean

The use of active acoustic to monitor abiotic structures and processes in the ocean have been gaining ground in oceanography. In some systems, acoustics allow the robust estimation of the depth of the pycnocline or thermocline either directly or indirectly when the physical structures drive the one of organisms. Here, we examined the feasibility of extracting the thermohaline structure (mixed-layer depth, upper and lower thermocline) from echosounder data collected in the oligotrophic Southwestern tropical Atlantic region at two seasons (spring and fall), more precisely in two areas with different thermohaline conditions, at both day and night. For that, we tested three approaches: (i) the vertical extension of the epipelagic community; (ii) the use of acoustic gradients; and (iii) a cross-wavelet approach. Results show that, even if the thermohaline structure impacts the vertical distribution of acoustic scatters, the resultant structuring did not allow for a robust estimation of the thermohaline limits indicating that other oceanographic or biological processes are acting. This result prevents for a fine-scale representation of the upper-layer turbulence from acoustic data. However, studying the proportion of acoustic biomass within each layer provides interesting insights on ecosystem structure in different thermohaline, seasonal and diel scenarios.

Composition and distribution of microplankton in the Barents Sea in connection with the thermohaline structure of the pelagial

The research is devoted to the microplankton from the southwestern part of the Barents Sea, which is under the influence of the central branch of the North Cape Current. The main patterns of distribution for individual species and general parameters of microplankton abundance in June 2019 were revealed. The key biological parameters such as the taxonomic composition of microplankton, level of total biomass and biomass of individual groups, characteristic species and species complexes were described for the water masses of the investigated area during the study.

Long-term and seasonal anomalies of the Sea of the Azov thermohaline structure for 1913 – 2018

Variability of temperature and salinity as well as quantifying global trends are fundamental for understanding changes in the Earth's climate. In current paper, a long-term variability of the hydrological regime of the Sea of Azov for 1913–2018 is studied. On the basis of oceanographic information, the seasonal variability of temperature and salinity by the areas of the Sea of Azov is analysed. Temperature anomalies have been revealed, periods of salinization and desalination of the Sea of Azov have been noted and linear trends of the anomaly have been obtained.

Spatial Characteristics of the Black Sea Cold Intermediate Layer in Summer, 2017

Purpose. The aim of the paper is to study spatial characteristics of the cold intermediate layer (CIL) after its waters were renewed due to the cold winter, using analysis of the data obtained during the Black Sea expedition in June 14 – July 3, 2017 (the 95th cruise of R/V “Professor Vodyanitsky”). Methods and Results. The data both from the CTD-measurements by the SBE911+ probe and the current velocity profile measurements by the Lowered Acoustic Doppler Current Profiler (LADCP) were used. Isopycnic averaging of the profile ensembles was applied to obtain the averaged characteristics of the water vertical thermohaline structure. During the measurement period, the minimum average temperature of the CIL core was 7.2°C at the density value 14.5 kg/m3. The layer upper boundary (according to the 8°C criterion) corresponded to the density value ~14.3 kg/m3, its lower one – to ~15.0 kg/m3. CIL water formation was most pronounced in the vicinity of the Rim Current, which was clearly seen on the isopycnic surfaces 14.6, and 15.0 kg/m3. According to the measurements, the main mass of CIL waters was identified in the Rim Current and in its right part (on the coast side). The CIL maximum thickness was ~60 m and the vertical position of its core corresponded to the 40–100 m depth. Conclusions. The synchronous profiles of current velocity, temperature, salinity, and density obtained in the Black Sea expedition in summer, 2017 made it possible to analyze the waters thermohaline structure with the regard for real dynamic situation. As a result, the CIL parameters, its spatial scales and position relative to the Rim Current were determined with due regard for the features of the density field structure in summer, 2017. This information can be useful for model verification and numerical experiments aimed at studying the mechanisms and the areas of CIL formation in the Black Sea.

Spatial Characteristics of the Black Sea Cold Intermediate Layer in Summer, 2017

Purpose. The aim of the paper is to study spatial characteristics of the cold intermediate layer (CIL) after its waters were renewed due to the cold winter, using analysis of the data obtained during the Black Sea expedition in June 14 – July 3, 2017 (the 95th cruise of R/V “Professor Vodyanitsky”). Methods and Results. The data both from the CTD-measurements by the SBE911+ probe and the current velocity profile measurements by the Lowered Acoustic Doppler Current Profiler (LADCP) were used. Isopycnic averaging of the profile ensembles was applied to obtain the averaged characteristics of the water vertical thermohaline structure. During the measurement period, the minimum average temperature of the CIL core was 7.2°C at the density value 14.5 kg/m3 . The layer upper boundary (according to the 8°C criterion) corresponded to the density value 14.3 kg/m3 , its lower one – to 15.0 kg/m3 . CIL water formation was most pronounced in the vicinity of the Rim Current, which was clearly seen on the isopycnic surfaces 14.6, and 15.0 kg/m3 . According to the measurements, the main mass of CIL waters was identified in the Rim Current and in its right part (on the coast side). The CIL maximum thickness was 60 m and the vertical position of its core corresponded to the 40–100 m depth. Conclusions. The synchronous profiles of current velocity, temperature, salinity, and density obtained in the Black Sea expedition in summer, 2017 made it possible to analyze the waters thermohaline structure with the regard for real dynamic situation. As a result, the CIL parameters, its spatial scales and position relative to the Rim Current were determined with due regard for the features of the density field structure in summer, 2017. This information can be useful for model verification and numerical experiments aimed at studying the mechanisms and the areas of CIL formation in the Black Sea