A laser method for remote determination of the distribution of capillary and gravity wave slopes on the sea surface is considered. The method illuminates the sea surface from top to bottom with a continuous laser beam and records scattered radiation below the point of incidence of the beam on the sea surface using a video camera. In the presence of intense capillary waves, the beam image has the shape of a light “skirt” that is formed below the point of incidence of the beam on the surface. It is shown that the distribution of capillary wave slopes along the axis perpendicular to the axis of the video camera can be determined from the distribution of light intensity in the cross-section of the light skirt. The distribution of slopes can be estimated almost instantaneously from one video frame in 0.01 s on a surface area of 50 cm2. Accumulating frames and averaging the illumination of the skirt over time τ makes it possible to estimate the distribution of slopes of all waves whose period is less than τ. The article presents the results of theoretical calculations and examples of field measurements in various meteorological conditions. The advantage of the method is the possibility of conducting measurements at almost any time of day, as well as the possibility of measurements from unmanned aerial vehicles.
To study the formation of dense shelf water and subsequent flow along the continental slope in the coastal area of the Cape Darnley Polynya during a specific period of its opening, the small-scale Fluidity ICOM model is used for the first time in a fully nonhydrostatic formulation. The model allows correct analysis of small-scale dynamics of density currents in mesoscale development. In calculations in the computational domain, the bottom topography is close to the actual one; the initial conditions are created in a preliminary experiment and are not specified. To calculate the intensity of intrawater (frazil) ice formation in a polynya, actual parameters of atmospheric forcing are used. The estimates of the values obtained for storm conditions: heat loss from the open water surface of the polynya, the rate of intrawater ice formation (ice productivity) and the intensity of salt fluxes into the water increase sharply (by an order of magnitude or more). In this connection, sharp intensification of convection in the polynya is observed, which enhances baroclinic circulation in the shelf-slope zone. Formed under the polynya, Antarctic shelf water spreads along the shelf and slope in the form of discrete unstable density currents, meanders, which often turn into eddies. In addition to the characteristic baroclinic instability, on bottom irregularities, the density currents also experience hydrodynamic instability, which ensures ventilation of waters on the slope. The bottom irregularities literally determine the cascading dynamics. Direct reliable estimates of the specific and volumetric flows of dense waters on the slope, obtained for conditions when the Cape Darnley Polynya is open, increase by six to seven times. In such areas of the slope in Antarctica, the formation of Antarctic bottom water increases sharply.
The problem of marine litter accumulation is relevant even in remote regions with low anthropogenic pressure, such as the Arctic seas. This study presents the results of three surveys conducted in 2021 and 2023 on the distribution and accumulation of macro- and microlitter in surface waters of the Kara and Barents seas. In 2021, an area of 18.3 km2 was observed, with 695 macrolitter items recorded (average: 4.56 items/km2; pollution density range: 0–210.6 items/km2). In 2023, 108 items were found over 9.4 km2 (average: 8.4 items/km2; pollution density range: 0–24.7 items/km2). Microlitter (1–5 mm) was analyzed based on 45 samples in 2021 (1.679 particles; mean concentration: 0.124 ± 0.383 items/m3; range: 0–1.53 items/m3) and 31 samples in 2023 (184 particles; mean: 0.02 ± 0.02 items/m3; range: 0–0.166 items/m3). Fishing nets were the main contributor to the mass of macrolitter. The average weight of microplastic was 0.0135 g/km2, while macrolitter amounted to 13.4 g/km2, which is 992.6 times higher.
Based on passive microwave remote sensing data, the dynamics of the area of sea ice and ice-free period (IFP) parameters in the East Siberian Sea were analyzed. The average annual start and end dates, as well as the duration of the IFP and rates of their changes for the period 1979–2022, were calculated. Also the features of the spatial and temporal distribution of the IFP parameters were described in the western and eastern parts, as well as in the entire water area, of the East Siberian Sea. From August to October, there is a significant decline in area of sea ice in the East Siberian Sea. This reduction has led to an increase in the duration of IFP. It is shown that during 1979–2022, the duration of he IFP in the East Siberian Sea increased statistically significantly by only 45
The comparison of satellite and visual cloud cover observations over the ocean is a crucial aspect of modern climatology and meteorology. Since 1853, visual cloud observations have been systematically conducted from commercial vessels, forming the basis of the extensive ICOADS dataset, which contains millions of ship-based meteorological reports distributed across the world’s oceans. Initially, cloud cover was measured in quarters of sky coverage, later transitioning to a ten-point scale in the first half of the 20th century. Since the 1950s, the eight-point scale (okta) has become the standard, where eight oktas represent complete cloud cover. The advent of satellite technology in the 1970s revolutionized cloud cover monitoring. Geostationary satellites like METEOSAT provide high-resolution data (0.05° × 0.05°) with multiple hourly images, while polar-orbiting satellites such as EPS/MetOP and POES/NOAA complement these observations. Comparing satellite and visual data presents two major challenges. First, visual observations cover approximately a 13–14 km radius from a height of 12–13 m, requiring proper spatial averaging of satellite data. Second, conversion between measurement units—from okta to percentage coverage—demands careful consideration. The study analyzed two primary datasets: ICOADS visual observations and COMET ed. 2.0 satellite data from 1983 to 2021 in the North Atlantic region. The research methodology included spatial averaging of satellite data, quality control of visual observations, daytime filtering, and exclusion of night observations due to lower accuracy. Analysis revealed several significant findings. Visual observers tend to underestimate cloud cover, sometimes by more than two oktas. Daytime observations showed higher accuracy than nighttime measurements. The research established clear thresholds: values below 6.25
