Search Results (18)

Arctic shipping lanes are gradually opening, creating an urgent demand for unmanned surface vehicles (USVs) capable of safe and efficient navigation in drifting-ice environments. However, dense, highly dynamic sea ice poses significant challenges for existing obstacle-avoidance approaches. This study proposes a dynamically weighted hybrid obstacle avoidance algorithm integrating an improved VO module and an enhanced APF module. The optimized VO method refines the velocity sampling strategy and incorporates DCPA/TCPA-based risk screening to eliminate high-risk candidate velocities. The improved APF method introduces adaptive parameter regulation, virtual-target-based local minimum escape, and historical-velocity-driven oscillation suppression. Furthermore, a real-time dynamic weighting mechanism is designed to balance the contributions of the VO and APF modules according to the instantaneous environmental risk level. Extensive simulation experiments demonstrate that the proposed algorithm achieves reliable collision avoidance performance, high navigation efficiency, and strong environmental adaptability for USVs operating in dynamic Arctic drifting-ice environments. Full article

A study was conducted on the interaction of surface gravity waves with a relatively thin, free-floating ice floe compared to the height of the waves. Physical and numerical modeling, as well as analytical research, were used. An overview of scientific works on the research topic is presented. The physical model consisted of an experimental setup (wave flume) with a wooden plate exposed to gravitational harmonic waves of different lengths and periods. The numerical model is based on calculations performed in the LS-DYNA program, where the fluid was simulated using the Euler–Lagrange method, and solid bodies were considered rigid. Analytical studies use the theory of interaction of small-amplitude waves with floating breakwaters. It is shown that as the wave height increases for conditions of interaction between waves and ice floes of almost identical horizontal dimensions, one end of the floating body sinks into the water, which leads to a significant reduction in the drift speed of the ice floe. Formulas have been obtained that express the ratio of the ice floe’s speed to the wave velocity, as well as the ratio of the height of the incident waves to the height of the transmitted waves, depending on the ratio of the wavelength to the horizontal dimensions of the floating ice floe. Full article

The presence of ice cover significantly alters the hydraulic characteristics of river channels, and the evolutionary law of ice drift velocity is crucial for understanding the ice-jam floods (IJFs) formation mechanism during the spring IJFs breakup period. Based on miniature ice buoy locators and Sentinel-2 satellite remote sensing data, this study systematically analyzes the channel characteristics of the upper Heilongjiang River and the regulatory effect of channel morphology on ice drift velocity. The results show that the river width of the upper Heilongjiang River exhibits a widening trend, with a variation range of 212 to 1292 m, characterized by large longitudinal dispersion and significant spatial variability. During the 2024 spring IJFs breakup period, the ice drift velocity ranges from 0.57 to 3.48 m/s with an average of 1.92 m/s, and a significant decreasing trend is observed when the ice drift passes through the entrances/exits of meandering bends and the confluences of distributaries in braided channels. The longitudinal distribution law of ice drift velocity revealed in this study can provide key data support and scientific reference for the accurate prediction of IJFs and the prevention and control of IJFs. Full article

Sea ice is highly dynamic. Differences in the sea ice drift velocity and direction can cause deformations such as ridges and rubble fields or open up leads. These and other deformations have a major impact on the interaction between the atmosphere, sea ice and the ocean, and strongly influence ship navigability in polar waters. Spaceborne Synthetic Aperture Radar (SAR) data is well suited to observing the sea ice and retrieving sea ice drift vector fields at a small scale (<1 km), revealing deformation zones. This paper introduces a software processor designed to retrieve high-resolution sea ice drift vector fields from pairs of subsequent SAR acquisitions using phase correlation embedded in a multiscale Gaussian image pyramid. We assess the accuracy of the algorithm by using drift buoys and landfast ice boundaries manually outlined from large series of TerraSAR-X acquisitions taken during winter and spring sea ice break up. In particular, we provide a first analysis of the localization accuracy in deformation zones. Overall, our experiments show that deformation zones are well detected, but can be misplaced by up to 1.1 km. An additional interferometric analysis narrows down the location of the landfast ice boundary. Full article

Global climate changes impact the Arctic seas by decreasing the sea ice area and changing the inorganic and organic matter supply via rivers and coastal permafrost thawing. Therefore, climate change may affect biogeochemical processes in the Kara Sea (KS) and Laptev Sea (LS), which form the Arctic Transpolar Drift. This study explores the effect of the KS shelf water supply on seawater parameters in the LS in late summer and early fall 2007, 2008, 2018, 2019, and 2024 using ship-borne (temperature, salinity, dissolved oxygen, nutrients, and pH), satellite-derived (sea surface heights, geostrophic current velocities), and model (current velocities) data. The results demonstrate that an inflow of KS shelf water with salinity of 33.0–34.5, high Apparent Oxygen Utilization values (50–110 µM), and increased concentrations of the dissolved inorganic phosphorus (DIP~ 0.7–1.2 µM), dissolved inorganic nitrogen (DIN~ 4–12 µM) and silicic acid (DSi~ 10–18 µM) enriches the subsurface layer of the LS with nutrients. The distributions of Atlantic—derived water (ADW) and KS shelf water in the LS from August to October depend on water dynamics caused by wind and river discharge. High Lena River discharge and westerly (downwelling favorable) winds promoted the supply of the KS shelf water to the LS through Vilkitsky Strait. In the area of the central trough of the LS, the KS shelf water can be modified by mixing with ADW. Mixing ADW with high DIN/DIP ratios (DIN~ 10 µM at DIP of 0.80 µM) and KS shelf water with low DIN/DIP ratios (DIN~ 8 µM at DIP of 0.80 µM) leads to changes in the DIN vs. DIP ratio in the subsurface layer of the LS. Full article

Accurate measurement of running parameters, including the step length (SL), step frequency (SF), and velocity, is essential for optimizing sprint performance. Traditional methods, such as 2D video analysis and inertial measurement units (IMUs), face limitations in precision and practicality. This study introduces and evaluates two methods for estimating running parameters using real-time kinematic global navigation satellite systems (RTK GNSS) with 100 Hz sampling. Method 1 identifies mid-stance phases via vertical position minima, while Method 2 aligns with the initial contact (IC) events through vertical velocity minima. Two collegiate sprinters completed a 400 m sprint under controlled conditions, with RTK GNSS measurements validated against 3D video analysis and IMU data. Both methods estimated the SF, SL, and velocity, but Method 2 demonstrated superior accuracy, achieving a lower RMSE (SF: 0.205 Hz versus 0.291 Hz; SL: 0.143 m versus 0.190 m) and higher correlation with the reference data. Method 2 also exhibited improved performance in curved sections and detected stride asymmetries with higher consistency than Method 1. These findings highlight RTK GNSS, particularly the velocity minima approach, as a robust, drift-free, single-sensor solution for detailed per-step sprint analysis in outdoor conditions. This approach offers a practical alternative to IMU-based methods and enables training optimization and performance evaluation. Full article

Changes in the masses of icebergs due to deterioration processes affect the drift of icebergs and should be taken into account when assessing iceberg risks in the areas of offshore development. In 2022 and 2023, eight laboratory experiments were carried out in the wave tank of the University Centre in Svalbard to study the melting of icebergs in sea water under calm and rough conditions. In the experiments, the water temperatures varied from $0 ℃$ to $2.2 ℃$. Cylindrical iceberg models were made from columnar ice cores with a diameter of 24 cm. In one experiment, the iceberg model was protected on the sides with plastic fencing to investigate the iceberg’s protection from melting when towed to deliver fresh water. The iceberg masses, water temperatures, and ice temperatures were measured in the experiments. The water velocity near the iceberg models was measured with an acoustic Doppler velocimeter. During the experiments, time-lapse cameras were used to describe the shapes and measure the vertical dimensions of the icebergs. Using experimental data, we calculated the horizontal dimensions of icebergs, latent heat fluxes, conductive heat fluxes inside the iceberg models, and turbulent heat fluxes in water as a function of time. We discovered the influence of surface waves and water mixing on the melt rates and found a significant reduction in the melt rates due to the lateral protection of the iceberg model using a plastic barrier. Based on the experimental data obtained, the ratio of the rates of lateral and bottom melting of the icebergs and lateral melting of the icebergs under wave conditions was parametrized depending on the wave frequency. Full article

Acquisition of continuous drift ice characteristic parameters such as ice size, shape, concentration, and drift velocity are of great importance for understanding river freezing and thawing processes. This study acquired hourly oblique images captured by a shore-based camera in the winter of 2021–2022 on the Yellow River, China. The pixel point scale method for correcting oblique images is provided. The 61 lines were measured at the calibration site and the absolute error between the measured value and the calculated value was in the range of 0.009–0.850 m, with a mean error of 0.236 m. After the correction of oblique images, the true equivalent diameter of drift ice during the freezing period ranged from 0.52–13.10 m with a mean size of 3.36 m, which was larger than that of 2.30 m during the thawing period which ranged from 0.20–12.54 m. It was found that the size of drift ice increased with time during the freezing period and decreased with time during the thawing period. The fractal dimension and roundness were used to represent drift ice shape. The fractal dimension ranged from 1.0–1.3 and the roundness ranged from 0.1–1.0. A Gaussian distribution was used to estimate drift ice size and shape distributions. There is a nonlinear relationship between ice concentration and drift velocity, which can be well expressed by the logistic function. In the future, drift ice parameters for more years and hydrometeorological data for the same time need to be accumulated, which helps to analyze the freezing and thawing patterns of river ice. Full article

This article contains the analytical model of the drift of a separate ice field under the action of wind and current, in which velocities and directions can vary over time. The model takes into account the mass of ice, added mass of seawater, and the effects of the wind and current on the ice field in forming the friction on its upper and underwater surfaces and the frontal resistance on its end (forward and backward) surfaces. Simulation of the wind drift of the ice field showed the drift velocity exceeds the considerable known velocity of a compact ice cover drift. A drifting ice field has a certain kinetic energy that should be released when a collision occurs with an unmovable obstacle, and spent on brittle breakdown of a quantity of the ice field. The volume of formed small ice pieces (fragments of ice field) was estimated by comparison of the specific energy of the sea ice brittle destruction and the kinetic energy of the drifting ice field. The article presents the results of the estimation of the possible volume of the ice pieces and the scales of formed piles as a result of a collision with an obstacle, depending on the initial dimensions of the ice field and wind speed. Developed models and the results of computer modeling can be used to estimate the ice pile sizes near the stationary platforms and terminals on the Arctic seas. Full article

Yellow River ice is the most prominent and significant natural disaster in winter and spring in China. During the drift ice period, water transmission tunnels located in this area tend to be hit by water–drift ice coupling. Thus, it is an important issue to reduce water transmission tunnel damage by drift ice, ensure the safety of operation and maintenance, and prevent engineering failure. In this paper, a numerical simulation of the collision process between ice and the tunnel is carried out by using the fluid structure coupling method and ANSYS/LS-DYNA finite element software. In addition, a model test with a geometric scale of 1:10 is carried out to verify the numerical simulation results, and the mechanical properties and damage mechanism of drift ice impacting the tunnel concrete lining in water medium are studied. The results show the following: the experimental values of maximum equivalent stress and X-directional displacement of the flow ice on the water transfer tunnel have the same trend as the simulated values, both of which show an increasing trend with an increase in flow ice velocity. It is shown that the ice material model parameters, ALE algorithm, and grid size used in this paper are able to simulate the impact of drift ice on the water transfer tunnel more accurately. With an increase in drift ice collision angle and drift ice size, the fitted curves of equivalent stress and peak displacement in X-direction all show relationships of exponential function. The peak value of displacement in the X-direction and maximum equivalent stress decrease with an increase in the curvature of the tunnel structure. It is also shown that the influence of change in drift ice size on the tunnel lining is greater than that of a change in tunnel section form. It is found that a high-pressure field will be formed due to extrusion of flowing ice, which should be fully considered in the numerical simulation. The research method and results can provide technical reference and theoretical support for prevention and control of ice jam disasters in the Yellow River Basin. Full article

The computational model was established to investigate the characteristics of oil spreading under arctic environments focusing on two aspects: ice concentrations and wave impacts. The ice field was constructed using the ice plates to compose three kinds of fixed arrays based on different ice concentrations of 90%, 60% and 0%. The wave was generated using the improved Jonswap spectrum method to control the focusing time, focusing location and focusing wave amplitude. The oil spreading’s movement was simulated and compared to the field experiment to verify the numerical model’s validity. The oil spill was trapped under the ice plates’ lower surface when the ice concentration was 60% or 90%, which had a spreading velocity slower than the non-ice water. The moving ice simulation was performed via the overset technique and coupled with the current, wind and wave. With ice drifting, the oil spreading was accelerated, leading to the presence of oil both on and under the ice surface. The ice was driven by the wave to affect the running details of the oil trajectory. These findings can be utilized for future oil spreading prediction when an oil spill accident occurs in the Arctic Ocean. Full article

Oceanographic and ice conditions in the region of Spitsbergen Bank in the Barents Sea were investigated in research cruises of the “Polarsyssel” in 2017–2019. Trajectories of ice drift were constructed using GPS data of the buoys deployed on the floes in the research cruises. The duration of the ice season in the region was analyzed using ice charts. The air temperature and wind velocities were analyzed using the data of meteorological stations on Bear Island and Hopen Island. Fieldwork on drifting ice showed the existence of thick consolidated floes with drafts up to 8 m, which were identified as completely consolidated sea ice ridges. The presence of such floes is dangerous for winter navigation along Spitsbergen Bank. A model of thermodynamic consolidation of ice ridges was formulated to investigate the thermodynamic evolution of ice ridges. The observed air and sea water temperatures were used in the boundary conditions on top and bottom surfaces of sea ice rubble. It was shown that the regular interaction of sea ice rubble with Atlantic and Arctic waters in the region of Spitsbergen Bank leads to almost complete consolidation of the ice rubble with an initial macro-porosity 0.2 for 150 days. Full article

In situ recordings by the solar Wind spacecraft reveal the ubiquitousness of alpha particles, whose drift velocities to the background proton $v_{\alpha }$ are generally less than or equal to the local Alfvén velocity $v_A$. The alpha beam instability plays a significant role in the alpha beam deceleration in the solar wind; nonetheless, the detailed mechanism of deceleration remains unclear. By using the linear Vlasov equation of the PDRK/B0 solver, the present work investigates the kinetic instability caused by both the alpha beam and the electron temperature anisotropy in the solar wind and assesses the effects of the electron temperature anisotropy on such instability. The results show that both anisotropic electrons and alpha beams lead to the excitation of several plasma waves, and the wave frequency, growth rate, and polarization properties are sensitive to the electron temperature anisotropy ($T_{e\perp }/T_{e\Vert }$), the parallel electron beta (${\beta }_{e\Vert }$), and the alpha beam drift velocity ($v_{\alpha }/v_A$). With an excess parallel temperature $T_{e\perp }/T_{e\Vert }<1$, the parallel magnetosonic/whistler (PM/W), parallel Alfvén wave (PAW), and oblique Alfvén/ion cyclotron (OA/IC) instabilities could be generated, while for an excess perpendicular temperature $T_{e\perp }/T_{e\Vert }>1$, the PM/W, OA/IC, parallel whistler (PW), and kinetic Alfvén wave (KAW) instabilities could grow. In the region of $T_{e\perp }/T_{e\Vert }<1$, the thresholds of the PM/W, PAW, and OA/IC instabilities extend to lower drift velocity $v_{\alpha }/v_A$. In the region of $T_{e\perp }/T_{e\Vert }>1$, the thresholds of the PM/W and OA/IC instabilities increase, while those of the PW and KAW instabilities are shifted to lower $v_{\alpha }/v_A$. The current study presents a comprehensive overview for alpha beam instabilities that limit the alpha beam drift velocity in the solar wind. Full article

In river management, it is important to obtain ice velocity quickly and accurately during ice flood periods. However, traditional ice velocity monitoring methods require buoys, which are costly and inefficient to distribute. It was found that UAV remote sensing images combined with machine vision technology yielded obvious practical advantages in ice velocity monitoring. Current research has mainly monitored sea ice velocity through GPS or satellite remote sensing technology, with few reports available on river ice velocity monitoring. Moreover, traditional river ice velocity monitoring methods are subjective. To solve the problems of existing time-consuming and inaccurate ice velocity monitoring methods, a new ice velocity extraction method based on UAV remote sensing technology is proposed in this article. In this study, the Mohe River section in Heilongjiang Province was chosen as the research area. High-resolution orthoimages were obtained with a UAV during the ice flood period, and feature points in drift ice images were then extracted with the scale-invariant feature transform (SIFT) algorithm. Moreover, the extracted feature points were matched with the brute force (BF) algorithm. According to optimization results obtained with the random sample consensus (RANSAC) algorithm, the motion trajectories of these feature points were tracked, and an ice displacement rate field was finally established. The results indicated that the average ice velocities in the research area reached 2.00 and 0.74 m/s, and the maximum ice velocities on the right side of the river center were 2.65 and 1.04 m/s at 16:00 on 25 April 2021 and 8:00 on 26 April 2021, respectively. The ice velocity decreased from the river center toward the river banks. The proposed ice velocity monitoring technique and reported data in this study could provide an effective reference for the prediction of ice flood disasters. Full article

The Ross Sea region, including three main polynya areas in McMurdo Sound, Terra Nova Bay, and in front of the Ross Ice Shelf, has experienced a significant increase in sea ice extent in the first four decades of satellite observations. Here, we use Co-Registration of Optically Sensed Images and Correlation (COSI-Corr) to estimate 894 high-resolution sea ice motion fields of the Western Ross Sea in order to explore ice-atmosphere interactions based on sequential high-resolution Advanced Synthetic Aperture Radar (ASAR) images from the Envisat satellite acquired between 2002–2012. Validation of output motion vectors with manually drawn vectors for 24 image pairs show Pearson correlation coefficients of 0.92 ± 0.09 with a mean deviation in direction of −3.17 ± 6.48 degrees. The high-resolution vectors were also validated against the Environment and Climate Change Canada sea ice motion tracking algorithm, resulting in correlation coefficients of 0.84 ± 0.20 and the mean deviation in the direction of −0.04 ± 17.39 degrees. A total of 480 one-day separated velocity vector fields have been compared to an available NSIDC low-resolution sea ice motion vector product, showing much lower correlations and high directional differences. The high-resolution product is able to better identify short-term and spatial variations, whereas the low-resolution product underestimates the actual sea ice velocities by 47% in this important near-coastal region. The large-scale pattern of sea ice drift over the full time period is similar in both products. Improved image coverage is still desired to capture drift variations shorter than 24 h. Full article