O. Yu. Lavrova

Anisotropic field of background internal waves on a sea shelf and its effect on low-frequency sound propagation

The space-time spectral characteristics of the field of background internal waves (IW) are obtained for two oceanic shelf regions (the Atlantic shelf of the United States and the Kamchatka shelf) and analyzed. Within the framework of a numerical experiment, it is shown that the observed anisotropy of the IW field may considerably affect the low-frequency sound fluctuations in the aforementioned regions and, in particular, may change the interference invariant of the sound field.

Catastrophic oil spill in the Gulf of Mexico in April–May 2010

The evolution of oil pollution in the Gulf of Mexico from April 20 to May 28, 2010, which resulted from the accident on the BP Deepwater Horizon oil platform that occurred on April 20, 2010, is reviewed. The development of the situation was traced on the basis of a joint analysis of optical and radar images (RIs), which proved to be very effective since the optical images made it possible to exclude the areas of calm on the RIs from consideration, and the RIs gave more complete information about dimensions of the areas covered with oil films indiscernible on optical images. It is shown that the mesoscale water dynamics is of prime importance in oil pollution transport in the gulf; therefore, almost all model predictions of a giant oil spill drift were not justified.

Observation of eddy structures in the Baltic Sea with the use of radiolocation and radiometric satellite data

The manifestations of mesoscale and submesoscale eddy elements in surface currents of the Baltic Sea in satellite images differing in physical nature and spatial resolution are considered. The investigation is based on the Envisat ASAR and ERS-2 SAR high-resolution radiolocation images (RLIs) obtained in 2008–2009 for different sites of the Baltic Sea water area and the use of the Envisat MERIS and Landsat ETM+ radiometric images of the visible spectrum. Possible mechanisms of the appearance of eddy structures in RLIs of the Baltic Sea water area are considered. Joint analysis of the mentioned data revealed specific features of the appearance of eddy structures in satellite images, taking into account the variability of optical characteristics of Baltic Sea surface waters during the summer blooming of cyanobacteria and the spring blooming of diatomic algae.

Satellite monitoring of oil slicks on the Black Sea surface

This paper summarizes the results of perennial combined satellite monitoring of the Black Sea conducted in order to detect sea-surface oil and oil-product pollution, as well as biogenic and anthropogenic surfactant films. A joint analysis of data obtained by various remote sensing techniques has been performed. The large amount of data has resulted in generalizations and reliable statistics on the spatial and temporal variability of different film manifestations in radar images of the sea surface. Regions most severely polluted by petroleum products have been identified. A hypothesis is suggested linking the surface manifestations of certain types of polluting films with natural gas and oil seeps and mud volcanism in the Black Sea. Improvements in the reliability of interpreting satellite data are discussed.

Study of internal wave generation and propagation features in non-tidal seas based on satellite synthetic aperture radar data

Despite the intense attention paid to internal wave (IW) investigation, the most experimentally studied and theoretically described are internal gravitational waves in shelf zones of oceans and tidal seas appearing during the interaction of tidal currents with the margin of the shelf. Information on surface manifestations of internal waves in enclosed seas, such as the Black and Caspian seas, is almost absent. In this paper, the results of study of the peculiarities of generation and propagation of nontidal internal waves are presented; the study is carried out on the basis of combined analysis in data of marine surface radiolocation and data of optical and infrared satellite-borne sensors. The experimental basis of investigation is radar images of the marine surface derived with the help of Synthetic Aperture Radars, onboard the Envisat and ERS-2 satellites. Additionally, the data of the following sensors belonging to the optical and infrared ranges were used for the purpose of radar image interpretation: MODIS (onboard the Aqua/Terra satellite), MERIS (Envisat), and AVHRR (NOAA). Surface manifestations of IWs in the northeastern part of the Black Sea and in the Caspian Sea have been found in radar imagery for the first time, their pattern of spatial and temporal variation has been reconstructed. The possible factors leading to generation of the observed nontidal IWs are determined and suppositions about the corresponding generation mechanisms are made. In particular, the IW manifestations recorded in the northeastern part of the Black Sea are localized in the vicinity of the boundaries of eddies or hydrological fronts; this fact evidences for the frontal mechanism of generation, at which IWs are radiated by a nonstationary (moving and/or inertially oscillating) front. The most probable main sources of generation of IWs detected in the Caspian Sea are longitudinal one-knot seiches, whose knot point is located near the Apsheron sill.

Satellite observations of surface manifestations of internal waves in the Caspian Sea

Results of satellite observations of surface manifestations of internal waves in the Caspian Sea are presented. It is proposed that the possible cause of generation of the revealed internal waves is uninodal seiches with a nodal line located in the vicinity of the Apsheron Sill. The basic parameters of internal waves in the Caspian Sea, having the form of classical soliton trains, are determined. Seasonal variability of surface manifestations of the internal waves is revealed. The horizontal current velocity of the solitons is assessed. According to the estimation, velocity is about 0.2 m/s, which is sufficient for wind ripple modulation.

Satellite monitoring of pollution in the Russian sector of the Azov and Black Seas in 2003–2007

The results of satellite monitoring of pollution in the Russian sector of the Azov-Black Sea basin in 2003–2007 are considered. Within the framework of this work, a technology of monitoring the state and pollution of the water environment from satellite information received during this period from Russian and foreign satellites has been developed. With this technology, the coastal pollution parameters and hydrometeorological characteristics of the water environment in the area of observation were mapped operationally; 14 types of different satellite information products were issued daily; and the results were generalized over 3 days, ten days, a month, and a period of observation. Long-term satellite monitoring makes it possible to determine and analyze typical situations of pollution distribution in the coastal waters and to detect new circulation elements that transport pollutants, thus purifying the water environment. For example, for the first time, it was found from satellite data that the contribution of a small-scale circulation of waters of the Russian sector of the Black Sea to the transport and distribution of pollutants is commensurable with the contribution of the Main Black Sea Current and coastal anticyclonic eddies. The regularities in the dynamics of pollution distribution promote the increased reliability of charting of the environmental situation, including the prediction of dynamics of pollution spreading.

Space monitoring of pollution of the Russian sector of the Azov-Black Sea basin in 2008

Technology of space monitoring of the state of water bodies and results of its application for studying the Azov-Black Sea basin in 2008 are considered. Based on the processing of more than 1000 satellite images and ground-based station data, basic characteristic features of the marine environmental pollution are determined which are connected with suspension dispersion, phytoplankton and algae growth, ship dumping of oil products (more than 62 oil patches were revealed), etc. The influence of dynamic structures in the coastal zone on the spatiotemporal distribution of the sea surface pollution parameters, and their contribution to mechanisms of water purification and self-purification are estimated. In particular, new data are obtained about the evolution of “Caucasian anticyclones,” about the dates of intensification of the Main Black Sea Current, and about features of coccolithophore bloom in the abyssal area of the Black Sea, etc.

Manifestation specifics of hydrodynamic processes in satellite images of intense phytoplankton bloom areas

The paper summarizes the results of the long-term complex satellite monitoring of the Black and Baltic seas. Data from synthetic aperture radars (SARs) constitute the experimental basis for the investigation of satellite. In addition to radar data, the data of the visible and infrared bands from MODIS Terra/Aqua, MERIS Envisat, Landsat series sensors are used. The features of the manifestation of hydrodynamic processes, submesoscale eddies in particular, in satellite radar and optical images in a period of intense phytoplankton bloom are discussed. A relationship is established between the intensity and duration of the phytoplankton bloom in the regions of observation and the frequency of the appearance of long-lasting wakes behind moving ships in SAR images. These wakes appear as long narrow bright bands of enhanced backscattered signal extending for tens and sometimes hundreds of kilometers. It is proposed to consider the wakes of this type as indicators of the areas and duration of intense phytoplankton bloom. Satellite observations over the Black and Baltic Seas conducted for more than ten years have shown that long-lasting ship wakes are influenced by powerful jet streams, such as those associated with the passage of eddies that leads to shifts and deformations. By comparing the true route of a ship with its wake in the satellite image, it is possible to obtain detailed information about the parameters of currents.

Fine spatial structure of flows on satellite radar image of the Baltic Sea

Satellite images of the sea surface demonstrate different dynamic processes at the water–air boundary and in the water layer. The objective of this investigation is to identify the fine structure of flows in the mesoscale vortex with the help of a specially developed method for flow estimation by ship wakes in the sea. The method described in this work made it possible to identify the jet nature and surges of flows in the mesoscale cyclonic vortex in the southern part of the Baltic Sea after long western and southwestern winds.