The Response of the Water Surface Layer to Internal Turbulence and Surface Forcing

We have carried out an experimental study of the turbulence kinetic energy dissipation rate (ϵ), temperature dissipation rate (χ), and turbulent heat flux (THF) within the water surface layer in the presence of non-breaking wave, surface convection, and horizontal heat and eddy fluxes that play a prominent role in the front. We noted that the non-breaking wave dominates ϵ values within the surface layer. While analyzing the vertical ϵ variability, the presence of a wave-affected layer from the water surface to a depth of z≈1.25λw is observed, where λw is the wavelength. ϵ associated with non-breaking waves ranged to 4.9×10−6–7×10−6 m2/s3 for the wavelength range of 0.038 m < λw < 0.098 m categorized as the gravity and gravity-capillary wave regimes. ϵ values increase for longer λw and non-breaking wave ϵ values represent their significant contribution to the ocean energy budget and dynamic of surface layer considering that the non-breaking wave covers the large fraction of ocean surface. We also found that the surface mean square slope (MSS) and wave generated ϵ have the same order of magnitude, i.e., MSS ∼ϵ. Besides, we have documented that the small-scale temperature fluctuation change (i.e., χ) is consistent with the large-scale temperature gradient change (i.e., d<T>/dz). The value of the THF is approximately constant within the surface layer. It represents that the measured THF near the water surface can be considered a surface water THF, challenging to measure directly.

MICROALGAE FROM THE COASTAL WATERS OF TYULENY ISLAND IN THE CASPIAN SEA

Aim. In this work, we set out to study the composition of a phytoplankton community in an important fishery area, the coastal water area of Tyuleny Island in the Caspian Sea.Methods. We present the results of seasonal observations (2016) on the state of phytoplankton in the coastal waters of Tyuleny Island in the Caspian Sea. In total, 120 phytoplankton samples were collected at four stations from the water surface layer (May–October) using the Nansen bottle and subsequent fixation by Lugolʹs solution. Sedimentation and concentration were carried out using standard procedures. The samples were processed in the Nageotte chamber with a volume of 0.1 ml under a light microscope.Results. According to the research results (2016), 103 species and varieties of microalgae were found in the phytoplankton samples collected from the water area of Tyuleny Island. The microalgae were represented by four divisions: Bacillariophyta – 49 species, Cyano‐ phyta – 24 species, Chlorophyta – 23 species and Pyrrophyta – 7 species. The greatest species diversity of phytoplankton in the studied water area was noted during the autumn period (61 spe‐ cies). In general, phytoplankton was found to be distributed homogeneously throughout the coastal area of the island, with the biomass concentration not reaching 1 g/m3.Conclusion. In 2016, favorable hydrological and hydrochemical conditions for the development of microalgae were observed. The desalinated water around Tyuleny Island, which is well warmed in the summer and does not freeze in the winter, contributed to the development of rich flora. Although bi‐ omass values were not high due to the prevalence of small‐celled microalgae in phytoplankton, in general, it should have a positive effect on the development of subsequent links in a trophic chain, as well as promote an increase in the productivity of waters of the Northern Caspian Sea.

STUDY OF BIO-OPTICAL CHARACTERISTICS OF THE BARENTS AND NORWEGIAN SEAS SURFACE LAYER WATERS IN SUMMER 2017

A study of the surface layer bio-optical properties of the Barents and Norwegian Seas in the summer of 2017 is carried out. Ship data were obtained during the 68th cruise of the R/V ‘Akademik Mstislav Keldysh’ (June-August 2017). Using a flow-through system, the fluorescence intensities of chlorophyll ‘a’ and dissolved organic matter as well as the salinity and temperature of the water surface layer along the ship’s route were continuously recorded. Seawater samples were taken for spectral fluorescence and absorbance measurements performed with a laser spectrometer and an integrating cavity absorption meter. The results are compared with the data of direct determinations of the chlorophyll concentration. Frequent continuous cloudiness prevented the use of ocean color data for the Norwegian Sea. In the coccolithophore bloom area in the Barents Sea, the results of shipboard measurements are compared with the data of OLCI satellite scanner. In this area, standard OLCI algorithms overestimate chlorophyll concentration, while the regression algorithm works better than based on neural networks. Comparison of the fluorescence and absorption spectra has shown the possibility of carrying out a rapid assessment of the chlorophyll concentration using optical methods. The change in the coefficients of the regression equations of chlorophyll fluorescence intensity and its concentration, determined by direct methods for different regions, is shown.

Evaluation of Equivalent Circulating Density in Deep Water Dynamic Kill Drilling

Dynamic kill drilling is a technology which is applied in order to control the deep water drilling shallow gas or shallow wells flowing by establish a normal cycle automatically in the deepwater shallow wells section. Equivalent circulating density (ECD) is an important parameters to control the bottom hole pressure, in the ECD estimate, if we don’t consider the effects of low temperature on rheological parameters of drilling fluid, it will result in errors in ECD estimates. Considering the impact of low temperature on the rheological parameters, this paper determines the temperature, rheological parameters and the annulus circulating pressure loss of each well section. Then Superposing each well section annular circulating pressure loss together, and finally calculate the equivalent circulating density. The deeper the water the greater of difference between ECD prediction model and the results calculated by rheological parameters on ground, and the more shallow wells the larger of difference. Therefore, in the process of deep water surface layer dynamic killing, We need to predict the equivalent circulating density of drilling fluids (ECD) accurately.