Ice-covered Waters Research Articles

Rapid fCO2 rise in the northern Barents Sea and Nansen Basin

Maps of surface water fugacity of CO2 (fCO2) over eastern Fram Strait, south-western Nansen Basin, and the north-western Barents Sea (73–84°N, 5–46°E) from September 1997 to December 2020 were made and used to investigate seasonal and temporal trends. The mapping utilized a neural network technique, the self-organizing map (SOM), that was trained with different combinations of satellite/observational/model data of sea surface temperature (SST), sea surface salinity (SSS), mixed layer depth (MLD), chlorophyll a (Chl a), sea ice concentration, and atmospheric mole fraction of CO2 (xCO2). The trained SOM was labelled with available surface ocean fCO2 data, and the labelled SOM was subsequently used to map the fCO2. The produced maps reveal that fCO2 in northern Barents Sea, at the border of the Nansen Basin, has increased significantly over the last decades by between 4.2 and 5.5 ± 0.6–1.1 µatm yr−1 over the winter to summer seasons. These rates are twice the rate of atmospheric CO2 increase, which was about 2 µatm yr−1. The spatial pattern coincides with the strongest decreases in sea ice concentration as well as with a salinification of the surface water. The former allows for a prolongation of the air-sea CO2 flux with resultant oceanic CO2 uptake in previously ice-covered waters, and the latter is caused by a shift from Arctic Water dominance to more saline waters containing more dissolved inorganic carbon, most likely of Atlantic Water origin although brine-release influenced deep water may also contribute.

Seasonality and drivers of water column optical properties on the northwestern Barents Sea shelf

Hydrographic and bio-optical measurements were conducted along a south–north transect on the northwestern Barents Sea shelf from early spring to late summer in 2021. Strong climate change manifestations observed in this region are rapidly changing the marine environment. These rare observations cover the seasonal evolution from well-mixed and sea ice-covered winter conditions, through sea ice retreat in spring, to late summer where the sea ice had largely retreated and the water column was stratified due to sea ice melt.Phytoplankton drives the spatial and temporal variability in optical properties in most of the water column, but increased scattering and absorption could also be seen in the bottom boundary layer due to resuspended particles. The relationship between chlorophyll-a and particulate absorption deviates from the globally observed relationship, likely due to light adaptations in the ice-covered water masses. We recommend developing specific models for spring phytoplankton growth in ice-covered waters to accurately account for self-shading effects. The absorption of colored dissolved organic matter (CDOM) was relatively low, due to waters of Atlantic origin in the studied region, and varied considerably less than particulate absorption. CDOM was nevertheless the optically dominant ocean constituent in the very clear waters in late winter.Regional relationships for estimating particulate organic carbon (POC) and chlorophyll-a concentrations from in situ attenuation and fluorescence measurements were developed. POC may act as an alternative indicator to chlorophyll-a for optical properties in ice-covered open ocean, which is relevant for light availability parametrizations in biogeochemical ocean models.

Freezing degradation of the anticonvulsant oxcarbazepine by bromate in water ice under sunlight irradiation

Ice plays a crucial role in contaminant transformation in seasonally ice-covered waters. In this study, the characteristics and mechanisms of an emerging contaminant oxcarbazepine (OXC) degradation by a disinfection by-product bromate (BrO3–) in ice were explored via combined experiments and theoretical calculations. Results showed that 74.0 % and 86.4 % of OXC was degraded by BrO3– in ice after 140 min in dark and 120 min under solar irradiation, respectively, while the reaction was negligible in water. The oxidation-reduction potential of BrO3– solution at 1000 μmol L−1 was 56.9 % higher than that at 50 μmol L−1. The oxidation-reduction potential of BrO3– solution at pH 2 was 14.8 %–109.5 % higher than those at other pH values. Enhanced OXC degradation by BrO3– in ice could be attributed to increased BrO3– oxidation capacity resulting from locally elevated BrO3– and H+ concentrations. Hypobromous acid (HOBr), •OH, and Br• generated by direct photolysis under solar irradiation further promoted the OXC degradation in ice. Br• formed by the direct photolysis of accumulated HOBr under solar irradiation caused the generation of bromine-containing degradation products. Bromine-containing degradation products possessed higher potential toxicities, which could contribute to increase the secondary pollution of water environment.

Diversity and seasonal development of large zooplankton along physical gradients in the Arctic Barents Sea

Due to ongoing climate change, a new Arctic Ocean ecosystem is emerging. Within the framework of the Nansen Legacy project, we investigated the community composition of the large zooplankton and its seasonal development along a latitudinal gradient in the northern Barents Sea. Total biomass was maximal in summer and early winter, and minimal in spring, with copepods contributing considerably in all seasons. Euphausiids represented a minor fraction of the biomass, whereas chaetognaths and other gelatinous zooplankton contributed substantially to the sampled zooplankton at all stations, particularly in winter. Amphipod biomass was high in early winter, but otherwise low. Temperature in the water column interior and bottom-depth had the highest explanatory power for the community composition of the large zooplankton, both revealing the same distinct Atlantic and Arctic domains along the studied section. The continental shelf of the northern Barents Sea had an Arctic signature and was in terms of biomass characterized by a dominance of cold-water species, such as Themisto libellula, and Calanus glacialis. The copepod Calanus hyperboreus was the dominant over the continental slope. Locations at the southern and northern end of the studied section were influenced by Atlantic Water (at intermediate depth at the northern stations), and contained a mixture of temperate species, deep-water species, and sympagic amphipods in northern ice-covered waters. In the northern Barents Sea, a seasonal change was observed in the biomass fractions of different zooplankton feeding guilds, with dominance of herbivores in summer and carnivores in winter. This suggests switching between bottom-up and top-down control through the year. On the continental slope, species that are typically considered omnivores seemed to increase in importance. The role of seasonally changing food preferences to bridge periods outside of the main primary production season is discussed in light of ecosystem resilience to the expected changes in the Arctic Ocean.

Detection of phosphates originating from Enceladus’s ocean

Saturn’s moon Enceladus harbours a global1 ice-covered water ocean2,3. The Cassini spacecraft investigated the composition of the ocean by analysis of material ejected into space by the moon’s cryovolcanic plume4–9. The analysis of salt-rich ice grains by Cassini’s Cosmic Dust Analyzer10 enabled inference of major solutes in the ocean water (Na+, K+, Cl–, HCO3–, CO32–) and its alkaline pH3,11. Phosphorus, the least abundant of the bio-essential elements12–14, has not yet been detected in an ocean beyond Earth. Earlier geochemical modelling studies suggest that phosphate might be scarce in the ocean of Enceladus and other icy ocean worlds15,16. However, more recent modelling of mineral solubilities in Enceladus’s ocean indicates that phosphate could be relatively abundant17. Here we present Cassini’s Cosmic Dust Analyzer mass spectra of ice grains emitted by Enceladus that show the presence of sodium phosphates. Our observational results, together with laboratory analogue experiments, suggest that phosphorus is readily available in Enceladus’s ocean in the form of orthophosphates, with phosphorus concentrations at least 100-fold higher in the moon’s plume-forming ocean waters than in Earth’s oceans. Furthermore, geochemical experiments and modelling demonstrate that such high phosphate abundances could be achieved in Enceladus and possibly in other icy ocean worlds beyond the primordial CO2 snowline, either at the cold seafloor or in hydrothermal environments with moderate temperatures. In both cases the main driver is probably the higher solubility of calcium phosphate minerals compared with calcium carbonate in moderately alkaline solutions rich in carbonate or bicarbonate ions.

Air quality impacts in the vicinity of a chemical herder mediated in-situ burn for Arctic oil spill response

Chemical herder augmented in-situ burning (ISB) is one of the most viable oil spill response techniques in partially ice-covered waters. Herein we report on the impacts of herder-mediated ISB tests on ambient air quality by making atmospheric measurements during ISB field tests in partially ice-covered waters in Fairbanks, Alaska. Concentrations of PM2.5, six combustion gases (CO, CO2, NO, NO2, NOx, SO2), volatile organic compounds (VOCs), and herding agent (OP-40) in the airborne plume (6–12 m downwind) were measured during three ISB events. PM2.5 concentrations significantly (p-value = 0.8014) exceeded NAAQS (24 h) exposure limits, while the remaining pollutants were found significantly (p-value <0.05) below the established exposure limits. OP-40 herder was not detected in the collected aerosol samples. To our knowledge, this is the first study on atmospheric emissions in the vicinity of a field-scale herder-augmented oil-spill ISB study in a high-latitude Arctic environment and provides information that is helpful to ensure the safety and well-being of on-site response personnel.

Influence of propeller on brash ice loads and pressure fluctuation for a reversing polar ship

When a polar ship is stuck in ice-covered waters, reversing operation is an effective way for it to escape from ice. During this operation, rotational propeller will affect flow field and motion of brash ice, thus affecting ice loads and pressure fluctuation. In this paper, a new coupling model using Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) is proposed to investigate characteristics of brash ice loads and pressure fluctuation for a polar ship reversing in a brash ice channel. The present method is well validated by model tests of a towing polar ship in brash ice channel. The simulation results show that in reversing process, brash ice blocks collide with the stern and two sides of ship, where ice blocks accumulate. When the reversing speed is low, the pumping action and acceleration effect of the propeller on the brash ice are obvious. The pumping action reduces the average value of the longitudinal and vertical ice loads, and the acceleration effect makes ice loads occur multiple peaks. The increase in reversing speed worsens the performance of propeller, weakening the pumping action and acceleration effect. The pressure fluctuation period is consistent with propeller rotation period, which decreases for poor propeller propulsion caused by higher reversing speed. It is necessary to strengthen the stern structure in reversing process, especially at low speed, for pumping action and acceleration effect of propeller.

Water wave diffraction by a submerged prolate spheroid in ice-covered water

Using the multipoles method, we formulate the problems of diffraction (both surge and heave) of water waves by a submerged prolate spheroidal body in deep water with an ice-cover, the ice-cover being modeled as an elastic plate of very small thickness. It investigates the linear hydrodynamic diffraction problem by prolate spheroidal body and obtains the analytical solution for the associated boundary value problem. The structural model is spheroidal with its polar axis greater than its equatorial diameter, subjected to the action of an incident wave. The hydrodynamic forces (surge and heave exciting forces) are obtained and depicted graphically against the wave number for various parameters and the flexural rigidity of the ice-cover is used to show the effects of the ice-cover on these quantities. When the flexural rigidity is zero, the numerical results for the forces for water with a free surface are recovered.

Distribution and photodegradation of typical nonsteroidal anti-inflammatory drugs in an ice-water system: Simulation of surface waters with an ice cover

In surface waters at middle and high latitudes during winter, the coexistence of ice and water is a natural phenomenon. Nonsteroidal anti-inflammatory drugs (NSAIDs) as emerging contaminants have been found frequently in aquatic environments, including waters that are seasonally covered in ice. However, little is available for the environmental behaviors and fate of NSAIDs in ice, particularly in the system where ice and water coexist. In this study, the distribution and photodegradation of model NSAIDs naproxen (NPX), diclofenac (DCF), and acetaminophen (APAP) in an ice-water system were investigated. The findings demonstrated a 66.7%, 60.5%, and 66.7% increase in the ice-water distribution coefficient Kiw of NPX, DCF, and APAP with initial concentrations of 10 ng L−1 relative to 500 ng L−1. The Kiw values were in decreased order of DCF, NPX, and APAP. The photodegradation rate constants of NPX, DCF, and APAP in ice increased by 27.0%, 35.6%, and 56.6% relative to those in water. With the increase in freezing time, the contribution ratios of distribution to the mass loss of NPX, DCF, and APAP increased by 19.9%, 21.1%, and 16.1%, respectively. The ratios of photodegradation to the mass loss of NPX, DCF, and APAP decreased by 5.0%, 5.7%, and 0.9%, respectively. An ice cover as the predominant factor could affect the distribution and photodegradation of drugs in the surface water. This study can close a knowledge gap regarding the transport and transformation of NSAIDs in the ice-water system and provide fresh insights into the behaviors and fate of emerging contaminants in seasonally ice-covered waters.

Coupled Vibration Analysis of Ice–Wind–Vehicle–Bridge Interaction System

Bridges built in ice-covered water regions are mostly in complex marine environments, they not only need to withstand strong wind but also resist the impact of drift ice. However, at present, there is a lack of vehicle–bridge coupling vibration analysis and driving safety assessment under combined ice and wind. Therefore, this study constructs a complete analysis framework of ice–wind–vehicle–bridge interaction to investigate the dynamic responses of the coupled system. Ice load is simulated by a linearized ice–structure interaction model, which is based on the self-excited vibration theory. Wind load on the bridge deck includes steady-state force and buffeting force. Wind load on the vehicle is simulated based on the quasi-steady model. Subsequently, ice load, wind load, soil–structure interaction (SSI), and additional water mass are all integrated into a full bridge model based on a sea-crossing bridge with running vehicles in the Bohai Sea. The results indicate that ice load has a greater impact on the lateral dynamic response of the bridge, the combined action of ice and wind has no superimposed effect on the movement of the bridge but has a restraining effect. Wind load presents a more significant influence on the lateral dynamic response of the vehicle, the coupled dynamic responses of the vehicle cannot be combined by the superposition under separate ice and wind. The combined effect of ice and wind obviously increases the sideslip risk of running vehicles and reduces driving safety.

Simulation and Key Physical Drivers of Primary Productivity in a Temperate Lake during the Ice-Covered Period: Based on the VGPM Model

The primary productivity of seasonal ice-covered water bodies is an important variable for understanding how temperate lake ecosystems are changing due to global warming. But there have been few studies on the complete change process of primary productivity during the ice-covered period, and the connection between ice physical and associated biological production has not been fully understood. In this study, a Vertically Generalized Production Model (VGPM) suitable for the ice-covered period was used to calculate the primary productivity of a temperate lake, and the key physical controlling factor was analyzed in the process of primary productivity change in the ice-covered period. The results showed that there was a high level of primary productivity, (189.1 ± 112.6) mg C·m−2·d−1, under the ice in the study site, Hanzhang Lake. The phytoplankton production under the ice was not as severely restricted by light as commonly thought. The water temperature played a more crucial role in the changes of primary productivity than the light beneath the ice. The study highlighted the variability in primary productivity covering the whole ice-covered age, and provided a better understanding of how the aquatic environment of lakes in seasonal ice-covered areas was affected by warmer temperatures.

Response of microbial communities in North Saskatchewan River to diluted bitumen and conventional crude under freeze-thaw-refreeze cycle

Microorganisms are the first responder to oil spills and their response provides insight into the ecological effects of oils on aquatic ecosystems. Limited information is available about the impact of oil spills on freshwater ecosystems under seasonal river-ice regimes. This study aimed to investigate the microbial response of North Saskatchewan River water to diluted bitumen (DB) and conventional crude (CC) during the freeze-thaw-refreeze cycle. In two separate experiments, equivalent to 2 L of fresh DB and CC were spilled on the ice-covered river water within a mesoscale spill tank. The microbial response (changes in abundance and diversity) to oils under the freeze, thaw, and refreeze cycles were assessed for 10 days using 16S rRNA gene sequencing. The results showed that microbial communities exhibited different responses to the DB and CC oils. The effect of oils was more pronounced than that of the freeze or thaw cycles. The river microbial community rapidly responded to both spills, which coincided with a steady increase in the organic content of water throughout the freeze-thaw-refreeze cycle. Microbial diversity increased after the DB spill, but remain unchanged after the CC spill, regardless of the cycles. A higher number of new taxa emerged during the ice-covered period, while more microbial enrichment (increase in abundance) was observed during the thaw cycle. Flavobacterium (37 ± 5%) and Pseudomonas (36 ± 4%) remained the most predominant genera post-DB and CC spill, respectively. The results of this study suggest that ice coverage of 5 cm did not prevent the microbial communities from the effects of oils. Thus, a quick clean-up response to an oil spill on ice-covered water is equally critical to avoid the effects of oils on the underlying freshwater ecosystems.

Features of Oil Spills Monitoring on the Water Surface by the Russian Federation in the Arctic Region

Given that the recent rapid growth of offshore production, especially in the Arctic region of the Russian Federation, is causing increased concern about oil spills on the water surface, this issue is especially relevant and important today. These pollutants have a devastating impact on the world’s marine biosphere. Therefore, effective and reliable methods and instruments must be used for operational spill detection in order to detect a remote oil spill. Several methods for oil spill monitoring and Russian developments in this area were described, including their features, advantages, and drawbacks. In cases when use in difficult Arctic conditions was anticipated, due to the harsh climate and ice-covered water surface, it was not always possible for spill detection instruments to be utilized. Despite this, such methods as radar, infrared, and ultraviolet were proven to be effective during this research. Ultimately, the combination of these methods returned the greatest volume of information to offshore platform staff about a detected oil spill. The information provided includes the spread area of the spill, the thickness of the leak, and the chemical composition of the oil.

Numerical Simulation of Oil Spill in the Arctic Ice-Covered Waters: Focusing on Different Ice Concentrations and Wave’s Impacts

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.

Goal-based Ship Design Towards Safe and Sustainable Shipping in Ice-Covered Waters

Maritime activity in the Arctic is on the increase, driven by the extraction of natural resources, trans-Arctic shipping, and tourism. To manage the risks to humans and the polar environment, in 2017 the IMO enforced the International Code for Ships Operating in Polar Waters (Polar Code). The safety provisions of this Code are fundamentally goal-based, allowing designers to deviate from established prescriptive safety rules, facilitating design optimization and innovation. However, to enable goal-based design, ship designers need relevant and validated design tools. In this paper, we present examples of such tools, namely (a) accident statistics, (b) a framework for risk-based design of Arctic ships, (c) a simulation model of a winter navigation system, and (d) a sustainability assessment tool for Arctic shipping. The results are based on three different European Union funded research projects (SEDNA, WINMOS I/II), as well as on the Lloyd's Register Foundation funded project CEPOLAR.

Oil spill response technology for ice-covered waters in the Arctic

A technology for removing oil spills from under the ice, based on the use of the vortex funnel effect, is proposed. A comparative analysis of methods oil pollution removal from under the ice cover is carried out. Models of the processes of separation of the “ice-oil-water” system occurring in the vortex funnel are presented, as well as, based on the experiment, photo illustrations of the stages of formation of the vortex funnel and removal of oil from under-ice. The schemes of deployment and operation of mobile equipment for removing oil spills from under the ice are proposed. It is shown that the proposed approach to liquidation of emergency oil spills in the Arctic can be used to create means and technologies of liquidation of more large-scale disasters of this kind.

Surface light modulation by sea ice and phytoplankton survival in a convective flow model

Plankton dynamics depend in a complex manner on a variety of physical phenomena, according to both experimental and numerical data. In particular, experimental field studies have highlighted the relation between phytoplankton survival and turbulent upwelling and downwelling from thermal convection. Recent numerical works have also shown the importance of accounting for advective transport by persistent structures in simulation models. In nutrient-rich polar marine environments phytoplankton blooms are critically limited by light availability under ice-covered waters. Such heterogeneity of the light intensity distribution, in association with a large-scale coherent fluid flow, can give rise to nontrivial growth dynamics. In this work we extend a previous advection-reaction-diffusion model of phytoplankton light-limited vertical dynamics in the presence of convective transport. Specifically, we consider horizontally heterogeneous light conditions through the use of two regions with different production regimes, modelling the absence (presence) of light under (in between) obstacles. Such a model is intended as an idealized representation of nonuniformly ice-covered polar waters. By means of numerical simulations, we find that the main role of advective transport is to hinder phytoplankton growth, but also that such effect depends on the positions of the obstacles with respect to the upwelling and downwelling flow regions. Furthermore, we show that the sinking speed due to the density difference between phytoplankton organisms and water, while small, plays an important role, which depends on how it adds to the flow. These results indicate that advective transport can have a crucial impact on the survival conditions of sinking phytoplankton species in polar environments.

Path planning for ships assisted by the icebreaker in ice-covered waters in the Northern Sea Route based on optimal control

This paper aims to develop an innovative model based on optimal control to optimize the shipping path of the fleet, including icebreakers and following ships in continuous time and space in the Northern Sea Route (NSR) waters, considering the influence of breakable and unbreakable ice. Path planning assumptions of ship navigation in ice-covered waters are summarized by considering navigation efficiency, navigation cost, icebreaking cost, and safety. The objective function of the model based on optimal control is formulated to convert the path planning problem into a multi-objective optimization problem. The cost functions based on path planning assumptions are specified in the objective function. Finally, dynamic programming and numerical simulation are used to solve the multi-objective optimization functions. Then, the optimal path in continuous time and space in ice-covered waters in the NSR is obtained. A case study of four scenarios, considering breakable and unbreakable sea ice conditions in the NSR, is conducted to verify the strength of the proposed model. The case study results show that the proposed model can optimize the path of ships in ice-covered waters. The method proposed in this research could guide ship fleet path planning for the bridge team and improve icebreaker management in the NSR.

Torsional vibrations of Polar-Class shaftlines: Correlating ice–propeller interaction torque to sea ice thickness

During ship operations in ice-covered waters, propellers often collide with sea ice pieces. This phenomenon represents a severe hazard that affects the torsional stress state of shafting systems and, ultimately, the ship propulsion system reliability. Classification Societies provide ship designers with design loads and criteria to simulate these events, but there are still uncertainties on the actual characteristics of the impacts that ice-class propellers undergo. This paper presents the results of a research activity that combines experimental measurements and numerical analysis to identify the correlation between ice-induced propeller loads and sea ice conditions. The Canadian Coast Guard (CCG) icebreaker Henry Larsen is considered a case study; we simulate its propulsion shaftline as a lumped-element system and validate this model against full-scale data. A series of numerical simulations to predict the ice-induced impact loads on the propeller was performed by using measured dynamic torque data as the analysis input. Finally, the resulting values were correlated with the ice thickness data acquired while the ship was operating. We compare this ice–propeller torque distribution with the homologous quantities calculated as per the current Polar Class framework. The results show high torque response values even when the ship operates in thin ice.

A three-dimensional ant colony algorithm for multi-objective ice routing of a ship in the Arctic area

The increasing shipping activities in the Arctic area pose challenges to a ship's safety and fuel saving in ice-covered waters. The optimal ship route planning can reduce the fuel consumption and navigation risk for ice-going ships in the Northeast Route. In this paper, a multi-objective ice routing model has been developed for searching optimal routes with two objectives, i.e., minimization of the fuel consumption and the total risk along a voyage, considering the time-varying ice data. Navigation risk is considered by applying a risk assessment model for Arctic navigation. A 3D-ACA (Three-Dimensional Ant Colony Algorithm) has been proposed and implemented in the developed ice routing model to make decisions on a ship's passing waypoints and sailing speeds along each waypoint. Finally, several case studies with different route planning objectives have been conducted to demonstrate the performance of the proposed model.