Changes In Ice Conditions Research Articles

Adaptation of Satellite Remote Sensing Algorithms for Retrieval of Environmental Parameters in the Caspian Sea

The state of the Caspian Sea ecosystems causes serious concern due to anthropogenic (oil and gas production and transportation) and natural reasons (climatic changes, extreme meteorological and hydrological phenomena, natural hazards and their frequency of recurrence, etc.). Climatic changes have already led to a sharp drop in the Caspian Sea level, an increase in sea surface temperature, changes in ice conditions in the Northern Caspian, the intensity of phytoplankton blooms, especially in the Southern Caspian, an increase in turbidity in coastal areas due to river runoff, and changes in the frequency and intensity of wind patterns. As a rule, such phenomena have a significant specific (more often negative) impact on the natural systems and infrastructure of the coastal zone. To understand the current state and climatic changes in the main parameters of the marine environment in the Caspian Sea and to carry out its comprehensive analysis, it is necessary to use remote sensing data and to determine correctly different environmental parameters. Our experience shows that in many cases standard algorithms for retrieval of these parameters from the remote sensing data that are elaborated, calibrated and validated for the open ocean conditions, are not valid for inland seas which have their own specific physico-geographical, oceanographic and meteorological conditions. The paper presents a review of new algorithms and techniques developed during the past decade for correct retrieval of sea surface temperature, water turbidity, suspended particulate matter concentration, as well as determination of ice cover, river plumes, and wind surge areas based first of all on Ocean Color Data: MSI Sentinel-2A, -2B; OLI/TIRS Landsat-8 and OLI-2/TIRS-2 Landsat-9. These algorithms have been introduced into the specialized information and analytical system “See the Caspian Sea” (STCS), designed for collecting, analyzing and visualizing satellite and meteorological data for the Caspian Sea region.

Metatranscriptomic analysis reveals dissimilarity in viral community activity between an ice-free and ice-covered winter in Lake Erie.

Winter is a relatively under-studied season in freshwater ecology. The paucity of wintertime surveys has led to a lack of knowledge regarding microbial community activity during the winter in Lake Erie, a North American Great Lake. Viruses shape microbial communities and regulate biogeochemical cycles by acting as top-down controls, yet very few efforts have been made to examine active virus populations during the winter in Lake Erie. Furthermore, climate change-driven declines in seasonal ice cover have been shown to influence microbial community structure, but no studies have compared viral community activity between different ice cover conditions. We surveyed surface water metatranscriptomes for viral hallmark genes as a proxy for active virus populations and compared activity metrics between ice-covered and ice-free conditions from two sampled winters. Transcriptionally active viral communities were detected in both winters, spanning diverse phylogenetic clades of putative bacteriophage (Caudoviricetes), giant viruses (Nucleocytoviricota, or NCLDV), and RNA viruses (Orthornavirae). However, viral community activity metrics revealed pronounced differences between the ice-covered and ice-free winters. Viral community composition was distinct between winters and viral hallmark gene richness was reduced in the ice-covered relative to the ice-free conditions. In addition, the observed differences in viral communities correlated with microbial community activity metrics. Overall, these findings contribute to our understanding of the viral populations that are active during the winter in Lake Erie and suggest that viral community activity may be associated with ice cover extent.IMPORTANCEAs seasonal ice cover is projected to become increasingly rare on large temperate lakes, there is a need to understand how microbial communities might respond to changing ice conditions. Although it is widely recognized that viruses impact microbial community structure and function, there is little known regarding wintertime viral activity or the relationship between viral activity and ice cover extent. Our metatranscriptomic analyses indicated that viruses were transcriptionally active in the winter surface waters of Lake Erie. These findings also expanded the known diversity of viral lineages in the Great Lakes. Notably, viral community activity metrics were significantly different between the two sampled winters. The pronounced differences we observed in active viral communities between the ice-covered and ice-free samples merit further research regarding how viral communities will function in future, potentially ice-free, freshwater systems.

Validation and Application of Satellite-Derived Sea Surface Temperature Gradients in the Bering Strait and Bering Sea

The Arctic is one of the most important regions in the world’s oceans for understanding the impacts of a changing climate. Yet, it is also difficult to measure because of extreme weather and ice conditions. In this work, we directly compare four datasets from the Group for High-Resolution Sea Surface Temperature (GHRSST) with a NASA Saildrone deployment along the Alaskan Coast and the Bering Sea and Bering Strait. The four datasets used are the Remote Sensing Systems Microwave Infrared Optimally Interpolated (MWIR) product, the Canadian Meteorological Center (CMC) product, the Daily Optimally Interpolated Product (DOISST), and the Operational Sea Surface Temperature and Ice Analysis (OSTIA) product. Spatial sea surface temperature (SST) gradients were derived for both the Saildrone deployment and GHRSST products, with the GHRSST products collocated with the Saildrone deployment. Overall, statistics indicate that the OSTIA product had a correlation of 0.79 and a root mean square difference of 0.11 °C/km when compared with Saildrone. CMC had the highest correlation of 0.81. Scatter plots indicate that OSTIA had the slope closest to one, thus best reproducing the magnitudes of the Saildrone gradients. Differences increased at latitudes > 65°N where sea ice would have a greater impact. A trend analysis was then performed on the gradient fields. Overall, positive trends in gradients occurred in areas along the coastal regions. A negative trend occurred at approximately 60°N. A major finding of this study is that future work needs to revolve around the impact of changing ice conditions on SST gradients. Another major finding is that a northward shift in the southern ice edge occurred after 2010 with a maxima at approximately 2019. This indicates that the shift of the southern ice edge is not gradual but has dramatically increased over the last decade. Future work needs to revolve around examining the possible causes for this northward shift.

Interannual variability (2000–2013) of mesopelagic and bathypelagic particle fluxes in relation to variable sea ice cover in the eastern Fram Strait

The Fram Strait connects the Atlantic and Arctic Oceans and is a key conduit for sea ice advected southward by the Transpolar Drift and northward inflow of warm Atlantic Waters. Continued sea ice decline and “Atlantification” are expected to influence pelagic–benthic coupling in the Fram Strait and Arctic as a whole. However, interannual variability and the impact of changing ice conditions on deepwater particle fluxes in the Arctic remain poorly characterized. Here, we present long-term sediment trap records (2000–2013) from mesopelagic (200 m) and bathypelagic (2,300 m) depths at two locations (HGIV and HGN) in the Fram Strait subjected to variable ice conditions. Sediment trap catchment areas were estimated and combined with remote sensing data and a high-resolution model to determine the ice cover, chlorophyll concentration, and prevailing stratification regimes. Surface chlorophyll increased between 2000 and 2013, but there was no corresponding increase in POC flux, suggesting a shift in the efficiency of the biological carbon pump. A decrease in particulate biogenic Si flux, %opal, Si:POC, and Si:PIC at mesopelagic depths indicates a shift away from diatom-dominated export as a feasible explanation. Biogenic components accounted for 72% ± 16% of mass flux at 200 m, but were reduced to 34% ± 11% at 2,300 m, substituted by a residual (lithogenic) material. Total mass fluxes of biogenic components, including POC, were higher in the bathypelagic. Biomarkers and ∂13C values suggest both lateral advection and ice-rafted material contribute to benthic carbon input, although constraining their precise contribution remains challenging. The decadal time series was used to describe two end-members of catchment area conditions representing the maximum temperatures of Atlantic inflow water in 2005 at HGIV and high ice coverage and a meltwater stratification regime at HGN in 2007. Despite similar chlorophyll concentrations, bathypelagic POC flux, Si flux, Si:POC, and Si:PIC were higher and POC:PIC was lower in the high-ice/meltwater regime. Our findings suggest that ice concentration and associated meltwater regimes cause higher diatom flux. It is possible this will increase in the future Arctic as meltwater regimes increase, but it is likely to be a transient feature that will disappear when no ice remains.

Связи изменений ледовой обстановки на Северном морском пути с движением планет Солнечной системы

The paper considers the progress in the hydrographic support for navigation in various parts of the Northern Sea Route in terms of improving the methods for developing tentative forecasts of interannual changes of ice conditions. Among the approaches to solve the task the authors take into account factors that do not depend on the uncertainty of regional climate changes in the future. One of such factors is the main mechanical process in the Solar System — the orbital planetary motion. The paper goal is to confirm the existence of water areas in the seas under study, changes in the ice coverage of which in the summer-autumn period can be significantly associated with planetary orbital motion factor. The authors apply statistical methods to achieve the study goal. As factual material on changes in the ice coverage of the sections of the Northern Sea Route, they use information of GLORYS12v1 and ICDC global reanalysis databases for the period 1993—2019 and 1979—2020 respectively. As a result the authors have revealed locations of the water areas, for which the reliability of the conclusion about the significance of the relationship under consideration in certain months is at least 90%. They have stated that the reliability of such inference is the highest for some water areas of the East Siberian Sea in October and the Chukchi Sea in November. To confirm the suitability of the identified links for the development of tentative forecasts of trends in interannual changes in the ice conditions on the Northern Sea Route, the authors insist on additional testing to check the resistance to updating the actual material.

Peculiarities of joint influence of navigation intensification and climate change on fast ice distribution in the Ob’ Bay

All year–round navigation in the Ob’Bay has been operating for more than ten years. In recent years it has been performed most actively at three points: the port terminals Sabetta and «Utrenniy» (on the opposite coasts in the northern part of the bay) and the oil loading terminal «Vorota Arktiki» (in the southern part of the bay, off cape Kamenny). Regular winter navigation to Sabetta began in 2013 and to cape Kamenny in 2015. In recent years, the number of vessels in November–May has already risen to about 380 per season. The winter navigation in the fast ice is performed along ice channels, which should impact on the fast ice stability. The aim of this research was to determine the influence of navigation on the fast ice distribution in the Ob’Bay in terms of climate changes. To analyze navigation impact on the fast ice distribution in the Ob’Bay, data on air temperature, ice conditions and number of vessels in the winter period were used in the work. The sum of the freezing degree days (FDD) was chosen as a parameter of winter conditions severity. The mean location of the south boundary of the flaw polynya per season was a parameter of the fast ice stability. Such an approach reduced the influence of short–term fluctuations of temperature and ice conditions. The data analysis carried out over the last 25 years has confirmed a significant influence of navigation on the fast ice distribution. It has been found that for the range from mean to mild winter conditions (an estimate using FDD), the dislocation of the flaw polynya boundary in the south direction amounted to 0.4–0.8 degrees of latitude (25–50 miles) because of winter navigation intensification. Winter conditions more severe than mean have not been recorded in the region over recent years. Therefore, such estimates were not obtained for them. The discovered changes of ice conditions are significant for the region. The transfer from fast ice to drifting ice of different types, forms and concentration will lead to the corresponding restructuring of other natural processes (water dynamics, litho-dynamic regime, etc). Subsequently the impact of hydrometeorological factors on engineering facilities can change, affecting the navigation conditions, scenarios of loading on the hydraulic structures, absolute loading values, etc. This is a factor to consider in the economic development of the region.

The complex construction of a glaciovolcanic ridge with insights from the 2021 Fagradalsfjall Eruption (Iceland)

Glaciovolcanic landforms provide global-scale records of paleoenvironmental conditions and yield insights into subglacial eruption processes. Models for the formation of glaciovolcanic ridges, or tindars, are relatively simple, proposing a monogenetic eruption and a fairly uniform stratigraphy with or without a single transition from effusive pillow lavas to explosive fragmental deposits. Others have suggested that tindars are more complicated. To build a more robust model for tindar formation, we conducted a field and geochemical study of Undirhlíðar ridge on the Reykjanes Peninsula in southwestern Iceland. We show that the ridge was built through a complex sequence of eruptive and intrusive events under dynamically changing ice conditions. Quarry walls expose a continuous cross-section of the ridge, revealing multiple pillow and fragmental units. Pillow lava orientations record the emplacement of discrete pillow-dominated lobes and the migration of volcanic activity between eruptive vents. Volatile contents in glassy pillow rinds show repeated pulses of pillow lava emplacement under glaciostatic conditions, with periods of fragmentation caused by depressurization. Variations in major elements, incompatible trace element ratios, and Pb-isotopes demonstrate that the eruption was fed from separate crustal melt reservoirs containing melts from a compositionally heterogeneous mantle source. A shift in mantle source signature of pillow lavas suggests that the primary ridge-building phase was triggered by the injection of magma into the crust. Within the growing edifice, magma was transported through dykes and irregularly shaped intrusions, which are up to 20% by area of exposed stratigraphy sequences. The model for tindar construction should consider the significant role of intrusions in the growth of the ridge, a detail that would be difficult to identify in natural erosional exposures. The 2021–22 eruptions from the adjacent Fagradalsfjall vents allow us to draw parallels between fissure-fed eruptions in subaerial and ice-confined environments and test hypotheses about the composition of the mantle underlying the Reykjanes Peninsula. Both Fagradalsfjall and Undirhlíðar ridge eruptions may have occurred over similar spatial and temporal scales, been triggered by mixing events, erupted lavas with varying mantle source signatures, and focused volcanic activity along migrating vents. Differences in composition between the two locations are not related to systematic lateral variations in the underlying mantle. Rather, the Undirhlíðar ridge and Fagradalsfjall eruptions capture complex interactions among the crustal magma plumbing system, mantle source heterogeneity, and melting conditions for a moment in time.

Divergent habitat use and the influence of sea ice concentration on the movement behaviour of ringed seals Pusa hispida in Labrador, Canada

Climate change and industrial activities are leading to significant ecological changes in the Eastern Canadian Arctic, with consequences for top predators, including ringed seals Pusa hispida. However, there remains a limited understanding of habitat use, constraining an understanding of the impacts of change on this culturally valued pinniped. A total of 20 ringed seals from 2 areas in Labrador with different geomorphic attributes (Saglek Fjord in the North, and Lake Melville, an estuarine ‘fjard’ in the South) were equipped with satellite-linked transmitters to characterize behaviour states, home ranges, core use areas and environmental variables. Lake Melville-tagged seals had a smaller home range than Saglek Fjord seals (84968 vs. 196886 km2). There was little spatial overlap in the home ranges (10%) and core use areas (0%) between the 2 areas, which were separated by 572 km. Lake Melville seals spent more time in a transiting state during open water conditions (26%) than during ice-covered periods (9%), probably due to an influence of sea ice concentration; they also spent more time in the area in which they were tagged (72%) than did Saglek Fjord seals (36%), increasing the risk of exposure to local contaminants associated with hydroelectric developments. Our results suggest that ringed seals in Lake Melville have better feeding opportunities but may be more vulnerable to changing ice conditions and contaminants compared to seals in Saglek. These results will support the development of a planned culturally based Marine Protected Area in Nunatsiavut and can inform efforts to remediate contaminant sources in the region.

IMPACT OF FLOODS IN THE KOLYMA RIVER DELTA ON NAVIGATION CONDITIONS IN THE EAST SIBERIAN SEA

The problem of improving the quality of medium- and long-term forecasting of changes in the ice situation on the Northern Sea Route, and in particular in the East Siberian Sea, where one of the methods for choosing waterways is the passage of vessels in the areas of flaw polynya, is considered. The hypothesis that in the summer months such changes can be significantly affected by the terms of floods onset in the Kolyma River Delta is tested. The data of the GLORYS12v1 global reanalysis supported by the Copernicus Marine Service are used as factual material on the ice cover and levels of the East Siberian Sea in the months from May to October of 1993-2019. The reanalysis is based on mathematical models of the NEMO family, verified using altimetry data from satellite measurements. Using the developed methodology for the selected periods of the year, the dates of sharp changes in the level and ice cover on the pre-estuary seaside of the Kolyma River are estimated. Using statistical methods, the validity of the stated hypothesis for a number of the East Siberian Sea areas, along which the shipping lanes of the Northern Sea Route pass, is confirmed. It has been established that the greatest influence of the floods terms on the ice situation and navigation conditions in such areas takes place in July. It has been shown that early floods in the Kolyma delta generally lead to an improvement in the ice situation, and late floods lead to its complication. The identified relationships are recommended for use in forecasting changes in ice conditions. The assumption that with further climate warming and a shift in the flood terms to earlier dates, it is possible that the ice conditions will become more complicated due to the freezing of the formed polynya, is made.

Impact of Floods in the Kolyma River Delta on Navigation Conditions in the East Siberian Sea

Problem of improving the quality of medium- and long-term forecasting of changes in ice conditions in the Northern Sea Route, and in particular in the east Siberian sea, where one of the methods of selecting waterways is the passage of ships in areas of ice-covered polynya. The hypothesis is verified that during the summer months, such changes may be significantly influenced by the timing of the onset of high water in the Kolyma River delta. Data from the global reanalysis GLORYS12v1 supported by the European Copernicus Marine Service were used as factual material on the ice cover and levels of the East Siberian Sea in the months of May to October 1993-2019. The analysis is based on mathematical models of the NEMO family verified by satellite altimetry data. Using the developed methodology, the dates of abrupt changes in level and sea ice extent on the Kolyma River estuarine seashore have been estimated for selected periods of the year. The study uses statistical methods to confirm the validity of the stated hypothesis for a number of areas of the East Siberian Sea, through which the shipping routes of the Northern Sea Route pass. It has been established that the greatest influence of flood timing on ice conditions and navigation conditions in such areas takes place in July. It is shown that early floods in the Kolyma delta generally lead to improvement of ice conditions, while late floods lead to complication of ice conditions. The identified relationships are recommended for use in forecasting changes in ice conditions. It has been suggested that with further climate warming and shifting of flood dates to earlier dates, the complication of ice conditions due to freezing of the formed polynya is not excluded.

Regime shift in sea-ice characteristics and impact on the spring bloom in the Baltic Sea

We evaluated the temporal and spatial trends of the hydrological (temperature and sea ice) and biochemical (chlorophyll-a concentration) characteristics in springtime in the Baltic Sea. Both are strongly affected by climate change, resulting in a decrease in the duration of sea-ice melting in the previous decade. A new regime of sea ice began in 2008 and in all basins of the Baltic Sea, a rapid warming during spring could be detected. Using satellite data, the temporal and spatial variations in spring bloom were analysed during severe and warmer winters. Using a coupled hydrodynamic-biogeochemical model, we tested the response of spring bloom to the changing ice conditions. The results of the modelling indicated that the presence of ice significantly influences the predicted chlorophyll-a concentration values in the Baltic Sea. Therefore, it is necessary that any coupled model system has a realistic ice model to ensure the best simulation results for the lower trophic food web as well.

Coastal Polynya Disrupts the Acoustic Backscatter Diurnal Signal Over the Eastern Laptev Sea Shelf

The diel vertical migration (DVM) of zooplankton is one of the largest species migrations to occur globally and is a key driver of regional ecosystems and the marine carbon pump. The dramatic changes in the Arctic environment in recent years, mainly associated with sea-ice decline, may have wide significance for the Arctic shelf ecosystems including DVM. Observations have revealed the occurrence of DVM in ice-covered Arctic waters, however, there have yet to be observations of DVM from the extensive Siberian shelves in the Eurasian Arctic and no analysis of how the sea-ice decline may affect DVM. Here, 2 yearlong time series of acoustic backscatter, collected by moored acoustic Doppler current profilers in the eastern Laptev Sea from August 1998 to August 1999, were used to examine the annual cycle of acoustic scattering, and therefore the annual cycle of DVM in the area. The acoustic time series were used along with atmospheric and oceanic reanalysis and satellite data. Our observations show that DVM did not occur during polar night and polar day, but is active during the spring and fall transition periods when there is a diurnal cycle in light conditions. DVM began beneath the fast ice at the end of polar night and increased in intensity through spring. However, the formation of a large polynya along the landfast ice edge in late March 1999 caused DVM to abruptly cease near the fast ice edge, while DVM persisted through spring to the start of polar day at the onshore mooring. We associate this cessation of synchronized DVM ∼1 month ahead of polar day with a predator-avoidance behavior of zooplankton in response to higher polar cod abundance near the polynya. During polar day, the intensity of acoustic scattering was attributed to the riverine suspended particles. Overall, our results highlight the occurrence of DVM on the Siberian shelves, the cessation of synchronized DVM when a polynya opens up nearby, and the potential impact of significant trends toward a more extensive Laptev Sea polynya as part of changing ice conditions in the Eurasian Arctic and their impact on the Arctic shelf ecology.

Prey selection of polar bears in Foxe Basin, NU, Canada: evidence of dietary flexibility in a specialized predator

AbstractEcological flexibility of a species reflects its ability to cope with environmental change. Although polar bears (Ursus maritimus) are experiencing changes in foraging opportunities due to sea ice loss, regional prey availability and environmental conditions will influence the rate and severity of these effects. We examined changes in polar bear diet and the influence of sea ice characteristics in Foxe Basin over an 18-year period. We combined previous fatty acid data from bears harvested from 1999 to 2003 (n = 82) with additional data from 2010 to 2018 (n = 397). Polar bear diets were diverse; however, ringed seal (Pusa hispida) was the primary prey throughout the sample period. Prey contribution varied temporally and spatially, and by intrinsic factors, while the frequency of prey in diets varied over time suggesting that diet estimates reflect the variability in available prey. Bowhead whale (Balaena mysticetus), although still a minor dietary component, has more than doubled in frequency of occurrence in diets in recent years in association with increased scavenging opportunities. Higher dietary levels of beluga whale (Delphinapterus leucas) and harbour seal (Phoca vitulina) were linked to later breakup date suggesting heavier ice conditions may promote access to both prey species. The flexible foraging strategies of bears in Foxe Basin may help mitigate their vulnerability to changes in prey distribution and habitat conditions. Our results provide insights into the importance of alternative and supplemental food sources for polar bears during phenological changes in ice conditions that will likely have consequences to Arctic community structure as warming continues.

Sea ice decline drives biogeographical shifts of key Calanus species in the central Arctic Ocean.

In recent decades, the central Arctic Ocean has been experiencing dramatic decline in sea ice coverage, thickness and extent, which is expected to have a tremendous impact on all levels of Arctic marine life. Here, we analyze the regional and temporal changes in pan-Arctic distribution and population structure of the key zooplankton species Calanus glacialis and C. hyperboreus in relation to recent changes in ice conditions, based on historical (1993-1998) and recent (2007-2016) zooplankton collections and satellite-based sea ice observations. We found strong correlations between Calanus abundance/population structure and a number of sea ice parameters. These relationships were particularly strong for C. glacialis, with higher numbers being observed at locations with a lower ice concentration, a shorter distance to the ice edge, and more days of open water. Interestingly, early stages of C. hyperboreus followed the same trends, suggesting that these two species substantially overlap in their core distribution area in the Arctic Ocean. Calanus glacialis and C. hyperboreus have been historically classified as shelf versus basin species, yet we conclude that both species can inhabit a wide range of bottom depths and their distribution in the Arctic Ocean is largely shaped by sea ice dynamics. Our data suggest that the core distribution patterns of these key zooplankton are shifting northwards with retreating sea ice and changing climate conditions.

Whole Community Metatranscriptomes and Lipidomes Reveal Diverse Responses Among Antarctic Phytoplankton to Changing Ice Conditions

The transition from winter to spring represents a major shift in the basal energy source for the Antarctic marine ecosystem from lipids and other sources of stored energy to sunlight. Because sea ice imposes a strong control on the transmission of sunlight into the water column during the polar spring, we hypothesized that the timing of the sea ice retreat influences the timing of the transition from stored energy to photosynthesis. To test the influence of sea ice on water column microbial energy utilization we took advantage of unique sea ice conditions in Arthur Harbor, an embayment near Palmer Station on the western Antarctic Peninsula, during the 2015 spring–summer seasonal transition. Over a 5-week period we sampled water from below land-fast sea ice, in the marginal ice zone at nearby Palmer Station B, and conducted an ice removal experiment with incubations of water collected below the land-fast ice. Whole-community metatranscriptomes were paired with lipidomics to better understand how lipid production and utilization was influenced by light conditions. We identified several different phytoplankton taxa that responded similarly to light by the number of genes up-regulated, and in the transcriptional complexity of this response. We applied a principal components analysis to these data to reduce their dimensionality, revealing that each of these taxa exhibited a strikingly different pattern of gene up-regulation. By correlating the changes in lipid concentration to the first principal component of log fold-change for each taxa we could make predictions about which taxa were associated with different changes in the community lipidome. We found that genes coding for the catabolism of triacylglycerol storage lipids were expressed early on in phytoplankton associated with a Fragilariopsis kerguelensis reference transcriptome. Phytoplankton associated with a Corethron pennatum reference transcriptome occupied an adjacent niche, responding favorably to higher light conditions than F. kerguelensis. Other diatom and dinoflagellate taxa had distinct transcriptional profiles and correlations to lipids, suggesting diverse ecological strategies during the polar winter–spring transition.

Cortisol levels in narwhal (Monodon monoceros) blubber from 2000 to 2019

Narwhals (Monodon monoceros Linnaeus, 1758) summering on northern Baffin Island are experiencing increases in vessel traffic related to an iron-ore mine operated by Baffinland Iron Mines Corporation; how this increase in vessel traffic may impact narwhal is currently unknown. Cortisol is a stress response hormone and a stress indicator in marine mammals. This study evaluated cortisol levels in narwhal blubber sampled during subsistence harvests prior to project-related vessel traffic (2000–2006), during project-related vessel traffic (2013–2019), and during a high-stress entrapment event that occurred in 2015. There was a significant increase in cortisol levels from pre- (0.81 ± 0.45 ng/g (±SE)) to during (1.81 ± 0.48 ng/g (±SE)) project-related vessel traffic (over 100% higher), and both were significantly lower than cortisol levels from animals sampled during an entrapment event (10.52 ± 0.59 ng/g (±SE)). Increased vessel traffic, changing ice conditions, altered Arctic food webs, increased predation pressure from killer whales, and cumulative impacts from these sources likely all contribute to increased stress levels for narwhals. Thus, there is a need for continued monitoring of stress responses (i.e., cortisol levels) and other health indicators in narwhals to understand how individual fitness and the population will be impacted over time.

ЛЕТНЯЯ КРОМКА ЛЬДОВ И ОСЕННИЕ СРОКИ УСТОЙЧИВОГО ЛЕДООБРАЗОВАНИЯ В МОРЯХ ЛАПТЕВЫХ, ВОСТОЧНО-СИБИРСКОМ И ЧУКОТСКОМ В 1981-2018 ГГ

The spatial and temporal variability of ice edge position at the end of the summer period, the dates of the beginning of stable ice formation in early autumn in the Russia’s Eastern Arctic seas (Laptev, East-Siberian, and Chukchi) during 1981–2018 together with climate changes in the 21st century are analyzed. The analysis of summer and autumn ice characteristics shows certain common features occurring for many years: since the beginning of the 21st century, ice conditions have significantly improved, which is due to the more Northern position of the ice border in August–September and later dates for the beginning of stable ice formation in September–October. On average for the period 2002–2018, the ice edge at the end of the period of clearance from ice shifted (as compared to 1981–2001) in a northerly direction by about 400–500 km. Observations did show that in 2003–2018, the beginning of stable ice formation in the autumn season (as compared to 1981–2002) occurred later by about three weeks. The maximum northward shift of the ice edge was first observed (since 2002) on the aquatory to the East of the New Siberian Islands, and then (since 2011) – to the West of them. The greatest anomalies of late dates (onset) of ice formation were first observed (since 2003) in the Chukchi Sea, then (since 2008) – in the Laptev Sea, and later (since 2014) – again in the Chukchi Sea. Long-term changes in the ice conditions occur according to the similar scenario: first, an anomaly of the latitudinal position of the edge or the date of the ice formation beginning was formed in the Eastern part of the studied aquatory, and then this anomaly shifted from East to West. At the same time, the anomaly diminishes in the East that makes it possible to interpret the observed natural changes as fluctuations of the «ice wave» type. Taking into account the wave features of changes in summer and autumn ice indicators, we can assume that in the 2020s we should expect a similar continuation of natural fluctuations in changes in ice conditions, which will be accompanied by a spatial shift of the ice edge in the South direction and relatively earlier dates for the beginning of ice formation.

On thinning ice: Effects of atmospheric warming, changes in wind speed and rainfall on ice conditions in temperate lakes (Northern Poland)

Northern Hemisphere lakes are losing their ice cover due to climate change. Here we explored six decades of observational data (1961–2017) showing trends in air temperature, wind speed and precipitation over northern Poland, as well as changes in the ice conditions for five lakes with different morphometry. We evaluated whether and to what extent climatic effects, including atmospheric warming, changing wind speed and rainfall during fall and winter, influence ice conditions in morphometrically different lakes in Northern Poland. Our analysis demonstrated that ice cover duration and thickness decreased at rates of 5.4 days decade−1 and 2.5 cm decade−1, respectively. Ice conditions were influenced (65–75%) by the direct effects of air temperature change and to some extent by an interaction of warming with wind speed and precipitation (5–10%). While stronger autumnal winds result in longer ice cover duration, the effect of precipitation is bimodal with either an enhancement of ice formation by autumnal rain or accelerated ice loss during spring. To project future changes in ice conditions, we used a 1D hydrodynamic lake model forced with four climate model projections under low, medium and high Representative Concentration Pathway (RCP) scenarios. Our simulations demonstrate that current ice conditions will stabilize under the low emission scenario (RCP 2.6) but decrease under both the medium and high emission scenarios (RCP 6.0 and 8.5). During the 21st century, the lakes are projected to lose their ice at a rate between 4.5- and 10-days decade−1 and ice thickness will decrease by between 3.0 and 5.0 cm decade−1. The rate of change will be greater in smaller rather than larger lakes and more so for those situated further inland. The probability of ice-free winters will increase for all lakes and among all future scenarios by between 4 and 69% with the highest potential frequency of ice-free winters in smaller and deeper but relatively wind-exposed lakes.

Drivers and consequences of apex predator diet composition in the Canadian Beaufort Sea.

Polar bears (Ursus maritimus) rely on annual sea ice as their primary habitat for hunting marine mammal prey. Given their long lifespan, wide geographic distribution, and position at the top of the Arctic marine food web, the diet composition of polar bears can provide insights into temporal and spatial ecosystem dynamics related to climate-mediated sea ice loss. Polar bears with the greatest ecological constraints on diet composition may be most vulnerable to climate-related changes in ice conditions and prey availability. We used quantitative fatty acid signature analysis (QFASA) to estimate the diets of polar bears (n = 419) in two western Canadian Arctic subpopulations (Northern Beaufort Sea and Southern Beaufort Sea) from 1999 to 2015. Polar bear diets were dominated by ringed seal (Pusa hispida), with interannual, seasonal, age- and sex-specific variation. Foraging area and sea ice conditions also affected polar bear diet composition. Most variation in bear diet was explained by longitude, reflecting spatial variation in prey availability. Sea ice conditions (extent, thickness, and seasonal duration) declined throughout the study period, and date of sea ice break-up in the preceding spring was positively correlated with female body condition and consumption of beluga whale (Delphinapterus leucas), suggesting that bears foraged on beluga whales during entrapment events. Female body condition was positively correlated with ringed seal consumption, and negatively correlated with bearded seal consumption. This study provides insights into the complex relationships between declining sea ice habitat and the diet composition and foraging success of a wide-ranging apex predator.

Analysis of Impact Assessment Practice and Mitigation for Shipping Activity in the Eastern Canadian Arctic

Marine traffic is increasing in the Canadian Arctic, largely because of changing ice conditions, a growing tourism industry, and natural resource extraction. Impact assessment (IA) is a primary instrument for managing the impacts of project development in the Arctic, but there has been limited analysis of the scope and application of IA for identifying and managing the impacts of shipping. This paper examines the impacts of shipping activity associated with mining projects in the eastern Canadian Arctic, including barge traffic and resupply vessels; the mitigation actions commonly prescribed in IA; and the key IA challenges facing decision-makers. Results show 71 impacts that may be considered common to IA applications for shipping, for which the mitigation strategies rely heavily on compliance-based measures and “best” practices to either minimize or avoid impacts, supported by follow-up programs that provide for adaptation of mitigation based on monitoring results. However, results also illustrate concerns over the ability of IA to effectively manage the cumulative effects of increasing Arctic marine traffic. Only a minority of projects involving marine transport trigger IA, even though other types of marine traffic, such as tourism, may generate similar types of impacts. The common impacts and mitigation solutions identified in this research and the lessons from monitoring can inform future IAs for shipping, improve permitting processes for shipping activities that do not require IA, and provide a foundation for a more regional or sector-wide approach to identifying and mitigating the cumulative effects of increasing vessel traffic.