Arctic warming is extending the open water period, increasing interest in oil exploration, extraction, and transport through the extended shipping season, consequently raising the potential for an oil spill in the Arctic. Remote sensing for oil detection and characterization is at the forefront of oil spill response efforts. Here, we show that the density of an oil is related to its complex dielectric constant (CDC), a governing factor of microwave remote sensing. The relationship between oil density (rho) and the real part of the oil CDC (epsilon(y)) as a function of composition and temperature was thoroughly investigated and a simple linear equation to describe the two variables was attained (epsilon(y) = 2.0396 rho+ 0.4961). Based on this oil density-CDC relationship, a framework was built for radar technologies to classify spilled oil as light, medium, heavy, or extra-heavy using forward and inverse modelling of the Normalized Radar Cross-Section to better inform responders on how to approach the oil spill and what mitigation procedures are most appropriate.

Rapid melting of sea-ice makes the Arctic more accessible for marine shipping and other industrial activities, increasing the risk of oil spills in the Arctic Ocean. Polycyclic aromatic hydrocarbons (PAHs) are among the most toxic substances in petroleum oil, yet their behavior in sea-ice-covered waters remains poorly studied. Here, we report an outdoor microcosm study to examine the partitioning behavior of four PAHs (naphthalene, phenanthrene, pyrene, and benzo(a)pyrene) across the seawater-sea-ice-atmosphere interface in the presence of particulate humic acid as a surrogate for particulate organic carbon (POC). We show that the higher the molecular weight of the PAH, the higher its concentration in sea-ice and the POC fraction. The POC-aqueous phase (seawater or bulk sea-ice) partition coefficients, Kd, are reasonably well explained by temperature and salinity for all four PAHs in seawater and for phenanthrene and pyrene in sea-ice. Relationships of Kd with temperature and salinity in sea-ice and freezing seawater are complex and nonunidirectional, most likely due to the dynamic nature of sea-ice and seawater under such temperatures. This suggests that conventional equilibrium-based approaches developed for open-water conditions need to be revisited when describing the behavior of PAHs in ice-covered waters.

Sea-ice conditions during a crude oil spill govern oil behaviour and the rate of weathering processes. This study utilized data from past mesocosm experiments conducted at the Sea-ice Environmental Research Facility and compared the sea-ice temperature, salinity, and chemical composition of light crude oil under three sea-ice conditions. An oil spill under discontinuous pack ice showed a decrease in ice thickness with an increase in oil concentration, as well as the highest photooxidation of organosulfur compounds amongst all experiments. An oil spill under a continuous ice volume demonstrated a decrease of sea-ice bulk salinity with an increase in crude oil concentration. Also, oil exhibited the lowest evaporation, along with the highest dissolution and carbonylation rates. An oil spill before ice formation demonstrated the reduction of sea-ice thickness and bulk salinity in contaminated ice. The oil in this case exhibited the highest evaporation and photooxidation rates. Tested oil-in-ice scenarios produced quantitative differences in sea-ice properties and crude oil composition.

The risk of oil spills in the Arctic is growing rapidly as anthropogenic activities increase due to climate-driven sea ice loss. Detecting and monitoring fuel spills in the marine environment is imperative for enacting an efficient response to mitigate the risk. Microwave radar systems can be used to address this issue; therefore, we examined the potential of C-band polarimetric radar for detecting diesel fuel in freezing seawater under windy environmental conditions. We present results from a mesocosm experiment, where we introduced diesel fuel to a seawater-filled cylindrical tub at the Sea-ice Environmental Research Facility (SERF), University of Manitoba. We characterized the temporal evolution of the diesel-contaminated seawater and sea ice by monitoring the normalized radar cross section (NRCS) and polarimetric parameters (i.e., copolarization ratio (Rco), cross-polarization ratio (Rxo), entropy (H), mean-alpha (α), conformity coefficient (μ), and copolarization correlation coefficient (ρco)) at 20° and 25° incidence angles. Three stages were identified, with notably different NRCS and polarimetric results, related to the thermophysical conditions. The transition from calm conditions to windy conditions was detected by the 25° incidence angle, whereas the transition from open water to sea ice was more apparent at 20°. The polarimetric analysis demonstrated that the conformity coefficient can have distinctive sensitivities to the presence of wind and sea ice at different incidence angles. The H versus α scatterplot showed that the range of distribution is dependent upon wind speed, incidence angle, and oil product. The findings of this study can be used to further improve the capability of existing and future C-band dual-polarization radar satellites or drone systems to detect and monitor potential diesel spills in the Arctic, particularly during the freeze-up season.

There is a heightened risk of an oil spill occurring in the Arctic, as climate change driven sea ice loss permits an increase in Arctic marine transportation. The ability to detect an oil spill and monitor its progression is key to enacting an effective response. Microwave scatterometer systems may be used detect changes in sea ice thermodynamic and physical properties, so we examined the potential of C-band polarimetric radar for detecting diesel fuel beneath a thin sea ice layer. Sea ice physical properties, including thickness, temperature, and salinity, were measured before and after diesel addition beneath the ice. Time-series polarimetric C-band scatterometer measurements monitored the sea ice evolution and diesel migration to the sea ice surface. We characterized the temporal evolution of the diesel-contaminated seawater and sea ice by monitoring the normalized radar cross section (NRCS) and polarimetric parameters (conformity coefficient (μ), copolarization correlation coefficient (ρco)) at 20° and 25° incidence angles. We delineated three stages, with distinct NRCS and polarimetric results, which could be connected to the thermophysical state and the presence of diesel on the surface. Stage 1 described the initial formation of sea ice, while in Stage 2, we injected 20L of diesel beneath the sea ice. No immediate response was noted in the radar measurements. With the emergence of diesel on the sea ice surface, denoted by Stage 3, the NRCS dropped substantially. The largest response was for VV and HH polarizations at 20° incidence angle. Physical sampling indicated that diesel emerged to the surface of the sea ice and trended towards the tub edge and the polarimetric scatterometer was sensitive to these physical changes. This study contributes to a greater understanding of how C-band frequencies can be used to monitor oil products in the Arctic and act as a baseline for the interpretation of satellite data. Additionally, these findings will assist in the development of standards for oil and diesel fuel detection in the Canadian Arctic in association with the Canadian Standards Association Group.

Oil thickness in oil spills involving sea ice is a key parameter required for an effective oil spill response; however, quantifying it from radar backscatter data remains a difficult task. We investigated a possible solution for estimating oil slick thickness by using electromagnetic (EM) forward and inverse scattering models of oil-covered newly formed sea ice (NI). Our forward model employs a first-order approximation of a multilayered small perturbation method (SPM) to predict two copolarization C-band radar backscatters of NI covered by an oil slick with thicknesses ranging from 0 to 7 mm. The results showed that the backscatter decreases as slick thickness increases, which we attributed to signal attenuation within the saline-oil layer. Our inverse model relies on the particle swarm optimization (PSO) algorithm to determine the slick thickness on NI using synthetic backscatter data, and it requires the input of several important ice and oil physical parameters (thickness, dielectrics, and roughness). Moreover, the estimated slick thickness was validated using scatterometer data from an oil-on-ice experiment at the University of Manitoba’s Sea-ice Environmental Research Facility (SERF). With synthetic data, the 5 mm oil slick thickness was overestimated by 25%, while with experimental data, it was overestimated by 8%. Overall, our findings have laid the groundwork for future inversion studies to identify the thickest oil spill zone from current and future C-band radar satellites for immediate response.

Petroleum-derived contamination is a growing hazard for the Arctic Ocean and northern marine transportation corridors. In northern settings where the accessibility to oil spills can be limited, natural attenuation is the most promising remediation process. The goal of the presented research is to evaluate the impact of biodegradation on crude oil inside sea ice. To this end, a bioremediation experiment was conducted at the Sea-ice Environmental Research Facility, University of Manitoba. The experiment utilized two mesocosm tanks (Augmented and Native) filled with nutrient-enriched artificial seawater (i.e., biostimulation). The water in the Augmented tank also contained oil-acclimated bacteria enriched from Arctic surface seawater from Cambridge Bay, Canada (i.e., bioaugmentation). The Native tank was not inoculated, but both tanks contained a bacterial community originating with the artificial seawater preparation. Crude oil was added under the naturally formed ice cover within each tank, creating areas that contained different oil concentrations. The Augmented tank contained 22 distinct bacterial genera compared to the Native tank, presumably due to the inoculation. The abundance of distinct bacterial genera was maximal in the water column and in low-contaminated ice core samples (<0.21 g oil/L). In these ice cores, bioaugmentation affected the concentration of low-molecular-weight aliphatic compounds (<C18) and naphthalenes (<C5). We also observed a 1% loss per day of n-nonadecane, n-docosane, methylphenanthrene, and tetramethylnaphthalene in the Augmented tank, which we attribute to bioaugmentation by the Arctic bacterial enrichment. In contrast, losses of these same compounds plateaued after day 15 in the Native tank.

We present a suite of polarimetric microwave scatterometers for Arctic remote sensing applications. The systems have been developed with L- (1.26 GHz), C- (5.5 GHz), and Ku- (17.2 GHz) band designs. The instruments were designed for near-surface operation and can be used to measure the normalized radar cross section in linear polarizations (VV, HH, and VH), as well as polarimetric parameters. The units use a frequency modulated continuous wave (FMCW) signal with pulse-to-pulse polarization switching. A mechanical positioner is used to orient the system to scan a region of interest. Herein, we describe the system technical parameters and the calibration routines. We provide sample data over a typical sea ice surface and describe system configurations. These systems are designed to provide multi-frequency polarimetric scattering data that can be analyzed for a wide variety of experiments in snow-covered sea ice and in Arctic oil spill studies.

The Arctic is a unique environment characterized by extreme conditions, including daylight patterns, sea ice cover, and some of the lowest temperatures on Earth. Such characteristics in tandem present challenges when extrapolating information from oil spill research within warmer, more temperate regions. Consequently, oil spill studies must be conducted within the Arctic to yield accurate and reliable results. Sites of the Baffin Island Oil Spill (BIOS) project (Cape Hatt, Baffin Island, Canadian Arctic) were revisited nearly 40 years after the original oil application to provide long-term monitoring data for Arctic oil spill research. Surface and subsurface sediment samples were collected from the intertidal zone of the 1981 nearshore oil spill experiment (Bay 11), from 1980 supratidal control plots (Crude Oil Point) and 1982 supratidal treatment plots (Bay 106). Samples were analyzed for Polycyclic Aromatic Hydrocarbons (PAHs) and alkylated homologues via Gas Chromatography - Mass Spectrometry (GC-MS). Our results suggest that total mean concentrations of all measured PAHs range from 0.049 to 14 mg/kg, whereas total mean concentrations of the 16 US EPA priority PAHs range from 0.02 to 2.1 mg/kg. The relative proportions of individual PAHs were compared between sampling sites and with the original technical mixture. Where available, percent loss of individual PAHs was compared with data from samples collected at the BIOS site, in 2001. All three sites featured samples where concentrations of various priority PAHs exceeded the established Interim Marine Sediment Quality Guidelines. All supratidal samples contained poten-tially toxic levels of PAHs. Even after nearly four decades of weathering, the recalcitrant crude oil residues remain a potential hazard for the native organisms. Continued monitoring of this unique study site is crucial for establishing a timeline for oil degradation, and to observe a reduction in toxicity over time.

Hudson Bay is a small arctic inland shelf sea which receives large amounts of freshwater from riverine discharges, with marine flow from the north and the Atlantic. A warming climate has resulted in an expanded open water season which will result in an increase in shipping of fuel oil and petroleum to communities and mines on the western shore, increasing the risk of hydrocarbon releases. To evaluate the status of hydrocarbons, surface sediments were collected at 34 locations in the transportation route and offshore and analysed for several types of hydrocarbons. Total hydrocarbons varied by over 25 times between sites, reaching a maximum of 1116 μg/g OC (organic carbon basis) in Hudson Strait due to low molecular weight n-alkanes from marine primary production. The gross mean for all sites was 344 μg/g OC (GSD = 173–682), roughly equivalent to other remote sites in the Canadian Arctic with no known local hydrocarbon source. n-alkanes accounted for >90 % of residues. Diagnostic ratios (e.g., Carbon Preference Index (CPI), Odd-Even Predominance (OEP)) indicated mixed sources of n-alkanes, likely due to the input from vascular plants and ombrotrophic peat in northern and western watersheds, and primary production within the Bay. The elevated proportion of high molecular weight n-alkanes at deep water sites is consistent with lotic particulate organic matter deposited in the nearshore environment and redeposited offshore. Ʃ36PAHs were a small fraction (1.9 %) of hydrocarbons, with a gross mean of 5.68 μg/g OC (GSD = 3.30–9.79). PCA separated deep water sediments from nearshore and community samples due to 4 alkylated naphthalenes which usually indicate a petrogenic source but probably indicates a natural source due to the lack of other petrogenic markers. Priority PAHs (i.e., Ʃ16PAH) varied from 31.5 % to 56.6 % of the Ʃ36PAH residues. The concentrations of individual PAHs were well below the Interim Sediment Quality Guidelines recommended by the Canadian Council of Ministers of the Environment.

Oil spills in the Arctic are becoming more likely as shipping traffic increases in response to climate-related sea ice loss. To improve oil spill detection capability, we used a controlled mesocosm to analyze the multipolarized C-band backscatter response of oil in newly formed sea ice (NI). Artificial sea ice was grown in two cylindrical tubs at the Sea-ice Environmental Research Facility, University of Manitoba. The sea ice physical characteristics, including surface roughness, thickness, temperature, and salinity, were measured before and after oil injection below the ice sheet. Time-series C-band radar backscatter measurements detected the differences in the sea ice evolution and oil migration to the sea ice surface in the oil-contaminated tub, which was compared to uncontaminated ice in a control tub. Immediately prior to the presence of oil on the ice surface, the copolarized backscatter is increased by 13-dB local maximum, while the cross-polarized backscatter is decreased by 9-dB. Ice physical properties suggest that the local backscatter maximum and minimum, which occurred immediately before oil migrated onto the surface, were related to a combination of brine and oil upward migration. The findings of this work provide a baseline data interpretation for oil detection in the Arctic Ocean using current and future C-band multipolarization radar satellites.

[para. 1]: "The Arctic is a sensitive ecosystem and a harbinger of global change. Indeed, the Arctic is warming at two to three times faster than the worldwide average, and polar bears, the Arctic's iconic top predator of the Arctic, are threatened. While global warming threatens the Arctic and its sensitive ecosystem, pollutio of Arctic waters poses another very real threa. The Arctic is the final "sink" or place of accumulation of many pollutants emitted from industrialised regions such as Northern America and Europe and well beyond. pollutants arrive in the Arctic by hemispheric air flows and by global water circulation patterns. Once i the arctic, pollutants resist degradation because of cold temperatures (which limit microbial degradation), and the Arctic has many dark months (which limits chemical degradation from sunlight). The Arctic ecosystem is also sensitive because pollutants are more available for accumulation by limited animal biomass. This availability is due to the limited "storage" capacity of the Arctic. For example, sparse Arctic soils do not allow for pollutant "storage" and "shielding" from biotic uptake, as is the case in temperate and tropical systems."

The Baffin Island Oil Spill (BIOS) Project is a long-term monitoring field study conducted in the early 1980s, seeking to examine the physical and chemical fate of crude oil released into a pristine Arctic setting. During the present study, sites of the BIOS Project were revisited in 2019 for the collection of oiled intertidal and backshore sediments. These samples were analyzed for several groups of petroleum hydrocarbons including saturates (n-alkanes, branched alkanes, and alkylcycloalkanes), hopane and sterane biomarkers, and alkylbenzenes. These hydrocarbon groups were present in concentrations ranging from 1.77-1210, 0.224-51.7, 0.0643-16.9, 0.00-11.7, and 0.0171-8.60 mg/kg within individual samples, respectively. When comparing current to limited results from past BIOS studies, a representative branched alkane (phytane), and medium-chain (nC18) and long-chain (nC30) n-alkanes demonstrate extensive weathering processes, exhibiting up to 90 %, 98 %, and 77 % loss since the penultimate BIOS revisitation in 2001, respectively.

Abstract Chlorpyrifos (CPY), a widely used organothiophosphate insecticide, has been proposed for listing on Annex A of the Stockholm Convention on Persistent Organic Pollutants. While CPY has been widely measured in Arctic air and seawater, information on bioaccumulation of CPY in aquatic food webs in the Arctic is very limited. This study presents results of additional monitoring data on CPY in fish and marine mammal samples from the Canadian Arctic/sub-Arctic based on ongoing studies under Canada’s Northern Contaminants Program. The majority of the CPY data was from samples collected from 2011 to 2021 and analysed using USEPA Method 1699, involving quantification by high resolution mass spectrometry. The available dataset showed low detection frequencies of CPY ranging from zero in arctic grayling (Thymallus arcticus) to 52% in arctic cod (Boreogadus saida). To enable statistical analysis the non-detects were substituted with ½ the detection limit (½ DL) based on the assumption that the non-detects were not zero and previous studies showing CPY was consistently detected in water and air in the Canadian Arctic. Largest geometric mean CPY concentrations were found in lake whitefish muscle (0.56 ng/g wet wt) while burbot liver had the highest maximum concentration (8.2 ng/g). Log10 CPY concentrations (with ½ DL substitution) were significantly correlated with % lipid and length in lake trout (Salvelinus namaycush) muscle and with % lipid in burbot (Lota lota) liver. Geomean concentrations in ringed seal (Pusa hispida) blubber from 8 communities ranged from 0.005 to 0.605 ng/g and showed no geo-spatial trends. Overall, the results indicate widespread but very low level contamination of Arctic fish and seals by CPY.

With an on-going disproportional warming of the Arctic Ocean and the reduction of the sea ice cover, the risk of an accidental oil spill from ships or future oil exploration is increasing. It is hence important to know how crude oil weathers in this environment and what factors affect oil biodegradation in the Arctic. However, this topic is currently poorly studied. In the 1980s, the Baffin Island Oil Spill (BIOS) project carried out a series of simulated oil spills in the backshore zone of beaches located on Baffin Island in the Canadian High Arctic. In this study two BIOS sites were re-visited, offering the unique opportunity to study the long-term weathering of crude oil under Arctic conditions. Here we show that residual oil remains present at these sites even after almost four decades since the original oiling. Oil at both BIOS sites appears to have attenuated very slowly with estimated loss rates of 1.8-2.7% per year. The presence of residual oil continues to significantly affect sediment microbial communities at the sites as manifested by a significantly decreased diversity, differences in the abundance of microorganisms and an enrichment of putative oil-degrading bacteria in oiled sediments. Reconstructed genomes of putative oil degraders suggest that only a subset is specifically adapted for growth under psychrothermic conditions, further reducing the time for biodegradation during the already short Arctic summers. Altogether, this study shows that crude oil spilled in the Arctic can persist and significantly affect the Arctic ecosystem for a long time, in the order of several decades.

Temporal trend analysis of (total) mercury (THg) concentrations in Arctic biota were assessed as part of the 2021 Arctic Monitoring and Assessment Programme (AMAP) Mercury Assessment. A mixed model including an evaluation of non-linear trends was applied to 110 time series of THg concentrations from Arctic and Subarctic biota. Temporal trends were calculated for full time series (6-46 years) and evaluated with a particular focus on recent trends over the last 20 years. Three policy-relevant questions were addressed: (1) What time series for THg concentrations in Arctic biota are currently available? (2) Are THg concentrations changing over time in biota from the Arctic? (3) Are there spatial patterns in THg trends in biota from the Arctic? Few geographical patterns of recent trends in THg concentrations were observed; however, those in marine mammals tended to be increasing at more easterly longitudes, and those of seabirds tended to be increasing in the Northeast Atlantic; these should be interpreted with caution as geographic coverage remains variable. Trends of THg in freshwater fish were equally increasing and decreasing or non-significant while those in marine fish and mussels were non-significant or increasing. The statistical power to detect trends was greatly improved compared to the 2011 AMAP Mercury Assessment; 70% of the time series could detect a 5% annual change at the 5% significance level with power ≥ 80%, while in 2011 only 19% met these criteria. Extending existing time series, and availability of new, powerful time series contributed to these improvements, highlighting the need for annual monitoring, particularly given the spatial and temporal information needed to support initiatives such as the Minamata Convention on Mercury. Collecting the same species/tissues across different locations is recommended. Extended time series from Alaska and new data from Russia are also needed to better establish circumarctic patterns of temporal trends.

There has been a considerable number of reports on Hg concentrations in Arctic mammals since the last Arctic Monitoring and Assessment Programme (AMAP) effort to review biological effects of the exposure to mercury (Hg) in Arctic biota in 2010 and 2018. Here, we provide an update on the state of the knowledge of health risk associated with Hg concentrations in Arctic marine and terrestrial mammal species. Using available population-specific data post-2000, our ultimate goal is to provide an updated evidence-based estimate of the risk for adverse health effects from Hg exposure in Arctic mammal species at the individual and population level. Tissue residues of Hg in 13 species across the Arctic were classified into five risk categories (from No risk to Severe risk) based on critical tissue concentrations derived from experimental studies on harp seals and mink. Exposure to Hg lead to low or no risk for health effects in most populations of marine and terrestrial mammals, however, subpopulations of polar bears, pilot whales, narwhals, beluga and hooded seals are highly exposed in geographic hotspots raising concern for Hg-induced toxicological effects. About 6% of a total of 3500 individuals, across different marine mammal species, age groups and regions, are at high or severe risk of health effects from Hg exposure. The corresponding figure for the 12 terrestrial species, regions and age groups was as low as 0.3% of a total of 731 individuals analyzed for their Hg loads. Temporal analyses indicated that the proportion of polar bears at low or moderate risk has increased in East/West Greenland and Western Hudson Bay, respectively. However, there remain numerous knowledge gaps to improve risk assessments of Hg exposure in Arctic mammalian species, including the establishment of improved concentration thresholds and upscaling to the assessment of population-level effects.

Decreases in Arctic Sea ice extent and thickness have led to more open ice conditions, encouraging both shipping traffic and oil exploration within the northern Arctic. As a result, the increased potential for accidental releases of crude oil or fuel into the Arctic environment threatens the pristine marine environment, its ecosystem, and local inhabitants. Thus, there is a need to develop a better understanding of oil behavior in a sea ice environment on a microscopic level. Computational quantum chemistry was used to simulate the effects of evaporation, dissolution, and partitioning within sea ice. Vapor pressures, solubilities, octanol-water partition coefficients, and molecular volumes were calculated using quantum chemistry and thermodynamics for pure liquid solutes (oil constituents) of interest. These calculations incorporated experimentally measured temperatures and salinities taken throughout an oil-in-ice mesocosm experiment conducted at the University of Manitoba in 2017. Their potential for interpreting the relative movements of oil constituents was assessed. Our results suggest that the relative movement of oil constituents is influenced by differences in physical properties. Lighter molecules showed a greater tendency to be controlled by brine advection processes due to their greater solubility. Molecules which are more hydrophobic were found to concentrate in areas of lower salt concentration.