Extensive research has established that both anthropogenic activities and river--tide interactions are significant factors affecting the sediment dynamics in estuarine and coastal regions. Particularly, it is considered that the narrowing and deepening of estuarine topography and decline in upstream discharge and sediment supply by anthropogenic activities (including reservoirs or dam construction, coastal reclamation, sand excavation, and channel dredging) may exert profound changes in the sediment dynamics characteristics of the Pearl River Estuary (PRE), a key region within the Guangdong-Hong Kong-Macao Greater Bay Area. To investigate the resulting impacts on sedimentary records, this study analyzed grain size distribution and loss-on-ignition (organic matter; OM) content from sediment cores collected from both eastern and western regions of the LE, the largest sub-estuary of the PRE, based on a ²¹⁰Pb-based chronological framework. The results reveal shifts in estuarine dynamics around 1994, marked by a 33 % reduction in sediment flux and amplified tidal energy, transforming the originally river-dominated estuary into a tide-dominated regime. Spatial heterogeneity in sedimentary responses was observed. In the eastern Lingdingyang Estuary (LE), sediment coarsening and improved sorting due to intensified tidal currents, while the western LE showed mixed deposition and poorer sorting linked to constrained ebb flows and sediment trapping effects. Furthermore, OM enrichment was strongly correlated with clay content, particularly in the western LE, indicating flocculation processes under tidal influence. OM accumulation increased westward but declined in the east. Our findings demonstrate that anthropogenic interventions dominate over natural processes in controlling estuarine sediment dynamics and provide essential understandings for sustainable management of the PRE and the Greater Bay Area while also offering a valuable reference for other heavily modified estuary systems worldwide.

The White Sea is a semi-enclosed basin of the Arctic Ocean connected to the Barents Sea by the narrow Gorlo Strait. Coastal polynyas of the White Sea are sections of open water or thin ice near the coast. Wind and dynamic processes, such as currents and tides, maintain them. The tides in the White Sea have a significant impact on the water's dynamics. Strong semidiurnal tides with amplitudes up to 9 m propagate through Gorlo, creating vigorous tidal currents throughout the sea. This large tidal range also causes daily reversed flow and intense mixing at straits, affecting polynyas situated in the Gorlo Strait and nearby areas. Landfast ice extends only a few kilometers from the shore. Tidal oscillations break it up. Polynyas vary yearly with ice conditions. Coastal polynyas influence regional climate, warming the surrounding areas. New young ice forms in polynyas. Brine rejection in polynyas affects local salinity, water density and mixing. Tidal forcing maintains coastal open-water areas via mechanical stirring and amplifies mixing in the coastal shelf, reinforcing the thermal- and haline-related effects of polynyas. Coastal polynyas detected from the coastal polynyas of the White Sea have not been well studied. Kupetsky was among the first to publish on this topic in the mid-20th century (Kupetsky, 1959). The complex configuration of the coastline and the presence of narrow bays determine the heterogeneous impact of the wind and consequently the location of polynyas. Due to water dynamics, modeling coastal sloughs is difficult and often yields inconsistent results. Therefore, satellite data seem to be a good option for studying the dynamics of polynyas. The initial data of the regional charts of the sea ice conditions in the White Sea from the World Sea Ice Data Center (http://wdc.aari.ru/datasets/) from 1999 to 2025 was used to prepare a dataset of polynya characteristics, including area, spatial position, and variability over time. The spatial and temporal variability of polynyas during the specified period was analyzed using the obtained time series.

Tidal fluctuations in sea level and currents are represented by a special set of harmonical functions. In a linear approximation, averaging of tidal fluctuations gives a result close to zero. However, in reality, due to nonlinear effects, such averaging will give a different result. This mechanism will lead to the appearance of a static sea level rise and the generation of a constant current. The change in the average sea level due to nonlinear effects is known as the residual tidal level. Permanent currents resulting from the transfer of energy from semi-diurnal and diurnal tidal waves are known as residual tidal currents, and the system they constitute is called residual tidal circulation.

The first description and explanation of residual tidal currents was given in the work of Timonov, 1960. Since then, numerous works have appeared describing residual tidal currents in various water areas. As a rule, residual tidal circulation was described based on the results of numerical hydrodynamic models. Specific conditions are required for reliable identification of residual tidal circulation in measurement data: strong tidal currents and limited influence of currents caused by other factors. Such conditions are observed in the semi-enclosed waters of the Keret Bay, where the Department of Oceanology of St. Petersburg State University has been conducting long-term research.

The investigation focused on Keret Bay in the Chupa Estuary and Kandalaksha Bay in the White Sea. There are small straits and bays, including the semi-enclosed Lebyazya Bay. The waters in a semi-enclosed basin have special features due to tidal cycles and topography. Numerical simulations and field observations revealed the unique characteristics of tide-induced circulation.

We employed a combination of numerous measurements and results of hydrodynamic simulations. The residual level and residual tidal circulation were calculated based on 30-day numerical experiment results. Filtering was performed twice using a moving average with a step of one day to eliminate harmonic components whose period is not a multiple of the length of the series. The values of the residual current and residual sea level were then determined from the filtered data.

The residual tidal sea level throughout the whole Keret Bay is practically absent. The deviation in the residual tidal level from the average sea level does not exceed a few millimeters. This is less than the accuracy of the methods used for analysis. The freshwater runoff from the Keret River will change the average sea level. It will also cause additional nonlinear effects associated with the interaction of river runoff and tidal waves.

The residual tidal currents obtained from model calculations are of most interest. Lebyazya Bay's permanent circulation, caused by tidal dynamics, is one of the most interesting special features. The characteristic flow velocities are 1-3 cm/s, reaching 5 cm/s. This circulation is a tide-induced permanent residual circulation, which is the result of the complex interaction of tides and topography.

A coupled circulation-ice modelling system with multi-grid nesting capacity was developed for the northwest Atlantic (CCIMS-nWA) based on the Regional Ocean Modeling System (ROMS) and Los Alamos Sea Ice Model (CICE). CCIMS-nwA is forced by atmospheric forcing (including winds, atmospheric pressure at the mean sea level and net heat and freshwater fluxes) at the surface, tidal forcing, inflows, hydrography and ice conditions specified at lateral open boundaries. The model external forcing also includes riverine freshwater discharges, and continental runoff due to melting of ice and snow over land. This paper provides an overview on different nested-grid setups developed by the regional modelling group at Dalhousie University for different projects. Performance of CCIMS-nwA is assessed using various data including in-situ oceanographic observations, satellite remote sensing data, and ocean reanalysis. Model results in two applications demonstrate the feasibility and skills of CCIMs-nwA in simulating both the large-scale hydrodynamics over the eastern Canadian shelf and fine-resolution currents and hydrography over three different coastal waters. These two different coastal waters include (a) southwestern Scotian Shelf, (b) Bras d’Or Lake of Cape Breton. The temporal and spatial variability of three-dimensional (3D) currents and hydrography simulated by this modelling system for these three coastal waters were examined based on time-dependent 3D model results.

Hurricane Fiona in late September 2022 was a large and destructive Category-4 Atlantic hurricane, with the wind gusts of about 180 km/h recorded at Arisaig of Nova Scotia. This storm was the most intense (and costly) extreme storm to hit Atlantic Canada on record, resulting in an issured loss of over 800 million Canadian dollar. A coupled wave-circulation model is used in this study to examine the storm-induced hydrodynamic changes and effects of wave-current interaction (WCI) during Hurricane Fiona. The coupled modelling system is based on the Regional Ocean Modeling System (ROMS) and the Simulating Waves Nearshore model (SWAN). Analysis of model results demonstrates very intense vertical mixing and currents generated by Hurricane Fiona in the surface mixed layer, both of which are biased to the right of the storm track. In addition to the strong wind forcing and large atmospheric pressure perturbations, the WCI plays a very important role in the hydrodynamic changes in the top ~80 m over the eastern Scotian Shelf and adjacent waters. Over the offshore deep waters (coastal waters) of the study region, the maximum significant wave heights (SWHs) reach up to 21 m (16 m), biased to the right of the storm track. The storm-induced near inertial currents are significantly stronger over the slope and deep waters compared to coastal and shelf waters.

The age composition of the Laptev Sea ice cover is considered. The seasonal course of the ice development, as well as interannual changes, was estimated from October to May in 1997-2024. Regional Laptev Sea charts of the ice conditions, compiled by the AARI (available in the electronic catalog of the World Sea Ice Data Center), were used as the data source. Regional charts are the result of analyzing satellite information in 2-3 days made as SIGRID-3 format. The spatial and temporal variability of sea ice with different stages of development (new ice, nilas, gray and gray-white ice, one-year thin, medium, thick and old ice) was analyzed using the method of probability calculated by polygon intersections.

Assessing the interannual variability of age composition during winter season, a tendency was revealed to shift the terms of the transition to the next age gradation to later ones, as well as a tendency to reduce the amount of the old and thick one-year ice, while the number of medium and young ice increased. The main factors determining the interannual changes in the area of ice of various age gradations for certain areas of the Laptev Sea were also considered. For this purpose, physico-statistical equations with the highest coefficients of correlation and determination were constructed, and optimal combinations of predictors were found to describe changes in the age composition of the sea ice cover.

An ice massif is a significant quasi-stationary accumulation of close or very close sea ice (with an ice concentration ranging from 7 to 10 tenths, and the concentration is the ratio expressed in tenths describing the amount of the sea surface covered by ice as a fraction of the whole area being considered, according to WMO Sea Ice Nomenclature). Ice massifs cover hundreds of square kilometers and are found in the same region every summer melting period.

Being an obstacle to navigation, ice massifs were first discovered in the 1940s with the help of air reconnaissance. These are also of interest now, since the development of the Arctic Sea shelf and related activities require safety and timing of work. We used data from the electronical archive of the Arctic and Antarctic Research Institute (AARI). The archive contains information on the year-round distribution of the ice cover in the form of maps and quantitative estimates of Arctic ice cover, including ice massifs. For assesment of interannual variability of ice massifs, we used a data set of quantitative estimates since 1940 to 2024 for June–September. For assessment of spatial distribution, we used regional Laptev Sea charts of the ice conditions, compiled by the AARI for June–September in 1997–2024. These data were analyzed using the method of probability calculation with polygon intersections. There are two ice massifs in the Laptev Sea: the Yansky ice massif, formed by fast ice in the eastern part of the sea, and the Taimyrsky ice massif, formed by a narrow fast ice and drifting ice in the western part of the sea. In summer, the Taimyrsky ice massif is fed by ice coming from the Arctic basin. By the end of the melting period, the Taimyrsky ice massif rarely disappears completely. However, during recent decades, the frequency of these events has increased. The Yansky massif consists mainly of fast ice, which lasts for a long time at the beginning of the summer period and quickly collapses after fast ice destruction. The Yansky massif disappears completely with very high frequency.

Drifting objects are the best proxy to elucidate the nature of the ocean surface currents. With the advancement of satellite tracked GPS, drifter observations offers a more comprehensive understanding of the spatial and temporal aspects of the ocean surface currents. North of Australia is a data sparse region from the oceanographers viewpoint. In the Browse Basin of Australia, The University of Western Australia deployed over 150 surface drifters during 2019 to 2022. This data was used to examine the seasonality in Lagrangian characteristics of the Browse basin surface currents, in the light of the wind data from the Adele island meteorological station of the Bureau of Meteorology. This extensive deployment revealed that the prominent mean currents in the region during the first indigenous season, Mangala (December to January) was directed northeastward due to winds from the southwestward direction. For the Marrul (April), Wirralburu (May), Barrgana (June-August), Wirlburu (September) through Laja (October-November) the surface currents were directed in a westward direction following the southeasterly winds. Furthermore, our drifters could capture the high frequency to low frequency variabilities in the surface currents like tides, inertial currents and eddies, which were not always captured in the satellite observations. The drifters also revealed a region of higher mixing which is in agreement with the higher kinetic energy imagery from satellite data.

During hurricanes and other extreme weather events, wave-current interactions are important over shelf and coastal waters. A state-of-the-art circulation-wave modelling system with parameterizations of Langmuir turbulence (LT) and wave breaking (WB) is used in this study to examine wave-current interactions during Hurricane Arthur (2014). Unlike previous studies, the effects of local topography on wave-current interactions are investigated during Hurricane Arthur. In particular, we focused on the dynamics within the Gulf of Maine and Gulf of St. Lawrence. The significant wave heights, vertical mixing and near-inertial currents all have highly asymmetric spatial distributions due to the proximity of the storm track to the coastline, which limits the fetch. Both LT and WB alter the storm-induced changes to the temperature and circulation in our results. Due to LT, the cold wake over the Mid-Atlantic Bight is enhanced by 0.5 °C. There is also clear LT-enhanced cooling over the area between the Gulf of Maine and the Scotian Shelf. However, the LT-enhanced cooling in the Gulf of St. Lawrence is mostly a cumulative effect from earlier storms. In the Mid-Atlantic Bight, WB increases horizontal advection. WB affects the momentum and cooling in the Gulf of Maine and Scotian Shelf asymmetrically, with larger impacts to the right of the storm track. WB also enhances the surface cooling in the southern part of the Gulf of St. Lawrence. Both LT and WB have a much bigger impact on the upper-ocean dynamics than the wave-induced bottom boundary layer and conservative Stokes drift effects.

The estuarine turbidity maximum (ETM) is typically found in tidal estuaries. The research on the ETM in non-tidal estuaries is comparatively limited. The presentation is focused on the ETM in the context of non-tidal Baltic Sea estuaries, particularly that of the Pregolya River, and is the first attempt to estimate the presence of ETM in the Baltic Sea river mouths environment. The study presents field measurement results examining the spatial distribution of temperature, salinity, turbidity, and suspended matter content along the Pregolya River estuary (South-Eastern Baltic). Measurements were taken monthly in 2024 to determine seasonal changes in these characteristics. It was found that ETM did not appear during the spring increase in river runoff, but formed during the period of low water, especially during the wind surges in the autumn. The biogenic component of suspended matter prevailed during the warm season. Lithogenic component prevailed at other times of the year (except during the spring runoff period). Results showed that ETM can occur under non-tidal conditions, exhibiting seasonal cyclicity and being driven by processes associated with the gravitational, colloidal-sorption, and biogenic stages. The microplastics (0.3-5 mm) and mesoplastics (5-25 mm) were investigated for the first time. The mean abundance of all plastics (0.3-25 mm) ranged from 7.7±5.1 to 15.7±4.9 items per litre. Fibres accounted for 98% of all plastic particles found. Two maxima in number and mass of plastic debris were found along the estuary, and it was hypothesised that the microplastic maximum is gradually formed by seasonal dynamics.