Ice-free Waters Research Articles

Arctic phytoplankton microdiversity across the marginal ice zone: Subspecies vulnerability to sea-ice loss

Seasonal phytoplankton blooms are important Arctic phenomena, contributing to global primary production and biogeochemical cycling. The decline in sea-ice extent and thickness favors a longer open-water period with impacts on phytoplankton dynamics. Arctic net productivity is influenced by microalgae living associated with sea ice, with distinct species thought to be favored by ice-covered and ice-free waters. In this study, we investigated the phytoplankton community structure in Baffin Bay, a semi-enclosed sea where Arctic and North Atlantic water masses interact. We compared communities from the ice-free Atlantic-influenced eastern, the marginal ice zone, and the ice-covered Arctic-influenced western Baffin Bay. The community was characterized using 18S rRNA high-throughput amplicon sequencing and flow cytometry cell counting, and compared to environmental data collected during the Green Edge campaign. We sampled 16 stations grouped by sectors according to sea-ice cover. In the sectors associated with sea ice, phytoplankton formed a highly diverse community of smaller taxa, which contrasted with a low-diversity community in ice-free sectors, dominated by larger centric diatoms and Phaeocystis pouchetii adapted to high light/low nutrient conditions. Several phytoplankton species were flagged as indicators for the under-ice and marginal ice zone sectors, including ice-associated taxa such as the diatoms Melosira arctica and Pseudo-nitzschia seriata, but also subspecies representatives of the early-blooming alga Micromonas polaris and the cryptophyte Baffinella frigidus. The strong association of certain taxa with under-ice and marginal ice zone sectors, including Pterosperma sp., Chrysochromulina sp., Micromonas polaris, and B. frigidus, suggest that they might be indicators of diversity loss due to ongoing sea-ice changes in Baffin Bay. We report new intra-species variability of Micromonas polaris suggesting that seasonal specialists could wax and wane over the bloom and non-bloom periods, highlighting the need for detailed year-long studies and the importance of microdiversity when assessing the diversity and distribution of polar phytoplankton.

Spatial trend analysis of significant wave heights in the Kara Sea

Over the past decades, the extent of sea ice in the Arctic, including the Kara Sea, has been diminishing. This phenomenon has a direct impact on wind waves as the increased expansion of ice-free water influences wave height. Furthermore, alterations in the ice cover also lead to modifications in atmospheric circulation, necessitating a concurrent analysis of wind and waves to refine the understanding of their interrelationships. In this study, wave modeling data were employed using the WAVEWATCH III model and NCEP/CFSR/CFSv2 reanalyzes. Calculations were performed on a non-structural computational grid. The grid covers the Barents and Kara Seas, as well as the entire northern part of the Atlantic Ocean. The spatial resolution varies from ~ 700 m for the coastal zone of the Kara Sea, to ~ 20 km in the open part of the Kara Sea, covering the period from January 1, 1979 to December 31, 2021. Subsequently, average significant wave heights (SWH), maximum SWH, and the 95th percentile of SWH were computed for each grid node on both monthly and yearly basis. The annual values were analyzed for trends and their significance. Calculations were conducted for both the entire period and ice-free period. Positive trends in annual mean values were observed throughout the sea, with the maximum trend occurring near the boundary with the Barents Sea, barely exceeding 0.2 m/10 years. The northern and northeastern parts of the sea were characterized by significant positive trends of the maximum SWH values. Maximum trend values for the 95th percentile of SWH were also evident in the northern part of the Kara Sea. For the ice-free period, maximum trend values were notable for both the annual mean and the 95th percentile of SWH in the northern part of the sea (maximum trend values are approximately 0.25 m/10 years and 0.5 m/10 years, respectively). Significant positive trends in the annual mean SWH were characteristic of the southern part of the sea, while the largest and significant trends for maximum wave heights were observed in the northeast. The assessment of the contribution of wind and ice regimes to the variability of wind waves remains a subject of discussion.

Declines in ice cover are accompanied by light limitation responses and community change in freshwater diatoms.

The rediscovery of diatom blooms embedded within and beneath the Lake Erie ice cover (2007-2012) ignited interest in psychrophilic adaptations and winter limnology. Subsequent studies determined the vital role ice plays in winter diatom ecophysiology as diatoms partition to the underside of ice, thereby fixing their location within the photic zone. Yet, climate change has led to widespread ice decline across the Great Lakes, with Lake Erie presenting a nearly "ice-free" state in several recent winters. It has been hypothesized that the resultant turbid, isothermal water column induces light limitation amongst winter diatoms and thus serves as a competitive disadvantage. To investigate this hypothesis, we conducted a physiochemical and metatranscriptomic survey that spanned spatial, temporal, and climatic gradients of the winter Lake Erie water column (2019-2020). Our results suggest that ice-free conditions decreased planktonic diatom bloom magnitude and altered diatom community composition. Diatoms increased their expression of various photosynthetic genes and iron transporters, which suggests that the diatoms are attempting to increase their quantity of photosystems and light-harvesting components (a well-defined indicator of light limitation). We identified two gene families which serve to increase diatom fitness in the turbid ice-free water column: proton-pumping rhodopsins (a potential second means of light-driven energy acquisition) and fasciclins (a means to "raft" together to increase buoyancy and co-locate to the surface to optimize light acquisition). With large-scale climatic changes already underway, our observations provide insight into how diatoms respond to the dynamic ice conditions of today and shed light on how they will fare in a climatically altered tomorrow.

Interannual variability in thermal state of the upper mixed layer in the Bering Sea in winter

Year-to-year variations of temperature in the upper mixed layer are considered for the ice-free waters of the Bering Sea in cold season (from December to March) using all data of the deep-sea oceanographic observations available to date (12,430 stations for the period from 1943 to 2022). Series of annual mean fields of the mixed layer temperature in December-March were decomposed by applying the empirical orthogonal function (EOF); dynamics of the first two components of decomposition (described in sum 50.4 % of the initial fields variability) are analyzed. The first component (32.4 % of variation) indicates synchronous oscillations over the entire sea area with the maximum contribution at the continental slope. The second component (18.0 % of variance) reflects opposite oscillations in two vast regions of the sea located along the continental slope from Cape Navarin to Alaska Peninsula and in the western, central and southern parts of the deep basin. The following statistically significant periodic oscillations are revealed by spectral analysis: quasi-biennial and those with periods of 4, 7, and 17–20 year for the 1st EOF and quasi-biennial and those with periods of 3 and 4 year for the 2nd EOF. A statistically significant linear trend to warming is detected for the time coefficient of the 1st EOF in the period of 1958–2022. Approximation of this coefficient dynamics with 6-degree polynomial function (polynomial trend) shows a tendencies to the mixed layer cooling in winters of 1969–1972 and 1992–2004 but the opposite tendencies to warming in 1973–1991 and 2005–2022. Variations of time coefficient for the 2nd EOF correspond to opposite tendencies in the areas with positive and negative values of this EOF. For the period from 1958 to 2022, winters in the Bering Sea are classified by the mixed layer temperature, taking into account the contribution of the 1st EOF only, as «warm» (1958, 1959, 1963, 1964, 1966, 1979, 1982, 1985, 1987, 1997, 2001, 2003, 2004, 2015–2018, 2020, and 2022), «normal» (1960–1962, 1965, 1967, 1968, 1970, 1971, 1974, 1978, 1980, 1981, 1983, 1986, 1989–1994, 1996, 1998, 2005–2007, 2011, 2013, 2014, 2019, and 2021), «cold» (1969, 1972, 1973, 1975–1977, 1984, 1988, 1995, 1999, 2000, 2002, 2008, and 2010), and extremely cold (2009 and 2012).

Inorganic carbon and nutrient dynamics in the marginal ice zone of the Barents Sea: Seasonality and implications for ocean acidification

The Barents Sea is a productive Arctic shelf sea experiencing Atlantification with ocean warming, sea ice loss and increased influence of Atlantic Water. The impact of these changes on inorganic carbon and nutrient dynamics and ocean acidification are yet to be fully understood. Seasonal variability and drivers of inorganic carbon and nutrients were determined from south of the Polar Front at 76 °N in the Barents Sea to 82 °N in the Nansen Basin, Arctic Ocean, encompassing Atlantic and Arctic regimes in summer (August 2019), winter (December 2019), winter/spring (March 2021) and spring (May 2021). Summer sea-ice meltwater was the main driver reducing total alkalinity (AT) and dissolved inorganic carbon (CT), corresponding to 55 % and 81 % of the total changes ΔCT and ΔAT, respectively, in the surface layer. Primary production reduced CT (37 % of ΔCT) and nutrients, particularly in ice-free waters, increasing calcium carbonate (CaCO3) saturation for aragonite (Ωaragonite) from 1.3 in spring to 2.3 in summer. Net community production (NCP) in the upper 50 m was highest (1.3 molCm−2) in the Atlantic Water regimes and lowest (0.4 molCm−2) in the ice-covered Nansen Basin in summer. Mixing, organic matter remineralisation and CO2 uptake enriched AT, CT and nutrients to pre-condition the water column from winter to early spring. Formation and dissolution of CaCO3 from shells and ikaite in sea ice (5–13 % of ΔAT) represented a minor AT source from winter to spring. Highest NCP by spring (0.3 molCm−2) occurred in a transient Atlantic-like regime over the shelf slope. Atmospheric CO2 uptake contributed up to 37 % of ΔCT and the region was an annual CO2 sink. Sea-ice processes and deep winter convection lowered AT and Ωaragonite (1.12–1.14) to enhance the risk of acidification over the shelf. Future Atlantification may increase biological production, reduce meltwater dilution effects and counteract acidification in the Barents Sea. The observations reveal the importance of seasonal and spatial studies to capture variability in inorganic carbon and nutrient cycling, driven by numerous processes coupled to the ice-ocean system that may exacerbate or alleviate ocean acidification in Arctic shelf seas.

Dynamic characteristics of unsteady cavity evolution of high-speed projectiles passing through holes in free surface ice flows

The free surface condition of water-entry problems will be significantly modified by the presence of an ice sheet on the water surface. In this paper, we employ computational fluid dynamics to simulate the process of a cylinder entering a water body vertically and validate the numerical method by comparing the cavity evolution with experimental data. Four high-speed water-entry cases are considered: an ice-free water surface, an ice sheet with circular holes, and an ice sheet with minor and normal sized petal-shaped holes. The cavity evolution, flow field characteristics, and motion parameters of the projectile after entering the water are analyzed separately, and the effects of the ice sheets with holes on the typical water-entry characteristics are identified. The results show that the cavity closure mechanism shifts from surface to shallow closure, and a funnel-shaped cavity is observed below the surface when ice is present. The size of the cavity is extremely restricted, but the collapse of the cavity is delayed. The pressure and flow characteristics around the projectile are also affected by ice on the water surface, and the stability of the trajectory is enhanced by the existence of the ice sheet. Finally, the positive acceleration of the projectile triggered by high pressure at the tail of the structure is found to be much larger than that in the ice-free case.

The Important but Mysterious Antarctic Krill

Antarctic krill are very important animals. They are well-known as the food of ocean giants such as blue whales, but they also feed many other animals and help to slow climate change by keeping millions of tons of carbon out of the air. Antarctic krill grow no longer than a human thumb, but together they weigh more than any other wild animal species. Although Antarctic krill live only in the cold waters of the Southern Ocean, they can live anywhere from sunlit surface waters to the darkest depths, from near the coast and under sea ice to ice-free waters far from land. In this article, we explore how their huge population and ability to live in diverse conditions make Antarctic krill important for other animals, people, and the world. We also introduce some key mysteries, such as what will happen to these animals as the climate continues to change.

Three forms of killer whales (Orcinus orca) in Antarctic waters

This paper provides field descriptions and biological observations of three different forms of killer whale (Orcinus orca) that occur in Antarctica based on field observations and a review of available photographs. Identifications were based on the relative size and orientation of the white eyepatch and the presence or absence of a dorsal cape. Type A (presumably the nominate form) has a medium-sized eyepatch oriented parallel to the body axis, no dorsal cape, it occurs mainly off-shore in ice-free water, has a circumpolar distribution and apparently preys mainly upon Antarctic minke whales (Balaenoptera bonaerensis). Type B also has an eyepatch oriented parallel to the body axis, but the eyepatch is at least twice as large as in Type A, it has a dorsal cape, mainly inhabits inshore waters, regularly occurs in pack-ice, is distributed around the continent and is regularly sighted in the Antarctic Peninsula area. Although it may also prey upon Antarctic minke whales and possibly humpback whales (Megaptera novaeangliae), seals seem to be the most important prey item. Type C has a small, forward-slanted eyepatch, a dorsal cape, inhabits inshore waters and lives mainly in the pack-ice; it occurs mostly off East Antarctica, and to date it has been recorded feeding only on Antarctic toothfish (Dissostichus mawsoni). Type C appears to be referable to Orcinus glacialis as described by Berzin and Vladimirov (1983). Although similar ecological specialisations have been reported for sympatric killer whale populations in the Northeast Pacific (i.e. an inshore mammal-eater, an inshore fish-eater and an offshore form), the extent of morphological divergence, habitat segregation and, perhaps, reproductive isolation, appears to be more pronounced among Antarctic populations. Although under a Biological Species Concept these forms appear to warrant separate species status, it will be important to show that this interpretation is consistent with results of molecular genetic analyses and additional morphological studies.

Neoproterozoic storm deposits in western Yangtze: Implications for the sea conditions during the middle Sturtian glaciation

The Neoproterozoic snowball Earth hypothesis emerged to explain an inferred planetary wide extreme climate change. However, storm deposits requiring open water conditions in the Huangdongzigou Formation, South China, contradict interpretations of a global Cryogenian hard snowball Earth. These deposits accumulated during the middle Sturtian interval (690–675 Ma) on the basis of U-Pb zircon age data from andesitic tuff and coarse siltstones within the formation. Siltstones and mudstones with abundant storm-generated erosional and sedimentary structures, such as hummocky and swaley cross-stratification occur through the sedimentary succession, which require the action of oscillating ice-free water flow. Chemical weathering indices and resultant mean annual temperature calculations indicate a warm-humid environment during storm events, with the transition to a cold water depositional environment towards the top of the formation, which is possibly related to the next glacial episode.

Current global population size, post-whaling trend and historical trajectory of sperm whales

The sperm whale lives in most deep ice-free waters of the globe. It was targeted during two periods of whaling peaking in the 1840’s and 1960’s. Using a habitat suitability model, we extrapolated estimates of abundance from visual and acoustic surveys to give a global estimate of 736,053 sperm whales (CV = 0.218) in 1993. Estimates of trends in the post-whaling era suggest that: whaling, by affecting the sex ratio and/or the social cohesion of females, reduced recovery rates well after whaling ceased; preferentially-targeted adult males show the best evidence of recovery, presumably due to recruitment from breeding populations; several decades post-whaling, sperm whale populations not facing much human impact are recovering slowly, but populations may be declining in areas with substantial anthropogenic footprint. A theta-logistic population model enhanced to simulate spatial structure and the non-removal impacts of whaling indicated a pre-whaling population of 1,949,698 (CV = 0.178) in 1710 being reduced by whaling, and then then recovering a little to about 844,761 (CV = 0.209) in 2022. There is much uncertainty about these numbers and trends. A larger population estimate than produced by a similar analysis in 2002 is principally due to a better assessment of ascertainment bias.

Ice Coverage of the Laptev Sea and Air Temperature Variation during Recent Centuries: Observed Data and Reconstructions Using a Geochemical Proxy

Objective: The aim was to reconstruct the climatic parameters and ice of the Laptev Sea over the last centuries and to identify the causes of their variability. Background: The ice-free water area of the Arctic Ocean has increased considerably during the summer–autumn period in recent decades, which may be attributed to several climatic and oceanographic factors. Methods: The ice-free period duration and mean annual surface air temperature were reconstructed using the transfer function technique to compare hydrometeorological data and the chemical composition of bottom sediments accumulated during the observation period. This approach was based on sub-millimeter scanning of sediments using synchrotron radiation X-ray fluorescence. The results revealed a specific feature of the variations in the mean annual air temperature over the last 400 years in the Laptev Sea region, whereby higher (up to positive) temperature anomalies, were observed during the Little Ice Age. Some discrepancies in the ice coverage and climate fluctuations were observed during the period from the end of the Little Ice Age to the beginning of the period of accelerated ice-cover degradation in the Arctic (1850–1980). These discrepancies can be caused by the beginning of global warming, which have disturbed the natural cyclicality of atmospheric processes, whereas natural variations in ice coverage were more stable. Conclusion: A joint analysis of the reconstructed variations in air temperature and the duration of the ice-free period revealed the influence of atmospheric processes on the ice conditions of the Laptev Sea.

Sea ice concentration impacts dissolved organic gases in the Canadian Arctic

Abstract. The marginal sea ice zone has been identified as a source of different climate-active gases to the atmosphere due to its unique biogeochemistry. However, it remains highly undersampled, and the impact of summertime changes in sea ice concentration on the distributions of these gases is poorly understood. To address this, we present measurements of dissolved methanol, acetone, acetaldehyde, dimethyl sulfide, and isoprene in the sea ice zone of the Canadian Arctic from the surface down to 60 m. The measurements were made using a segmented flow coil equilibrator coupled to a proton-transfer-reaction mass spectrometer. These gases varied in concentrations with depth, with the highest concentrations generally observed near the surface. Underway (3–4 m) measurements showed higher concentrations in partial sea ice cover compared to ice-free waters for most compounds. The large number of depth profiles at different sea ice concentrations enables the proposition of the likely dominant production processes of these compounds in this area. Methanol concentrations appear to be controlled by specific biological consumption processes. Acetone and acetaldehyde concentrations are influenced by the penetration depth of light and stratification, implying dominant photochemical sources in this area. Dimethyl sulfide and isoprene both display higher surface concentrations in partial sea ice cover compared to ice-free waters due to ice edge blooms. Differences in underway concentrations based on sampling region suggest that water masses moving away from the ice edge influences dissolved gas concentrations. Dimethyl sulfide concentrations sometimes display a subsurface maximum in ice -free conditions, while isoprene more reliably displays a subsurface maximum. Surface gas concentrations were used to estimate their air–sea fluxes. Despite obvious in situ production, we estimate that the sea ice zone is absorbing methanol and acetone from the atmosphere. In contrast, dimethyl sulfide and isoprene are consistently emitted from the ocean, with marked episodes of high emissions during ice-free conditions, suggesting that these gases are produced in ice-covered areas and emitted once the ice has melted. Our measurements show that the seawater concentrations and air–sea fluxes of these gases are clearly impacted by sea ice concentration. These novel measurements and insights will allow us to better constrain the cycling of these gases in the polar regions and their effect on the oxidative capacity and aerosol budget in the Arctic atmosphere.

The same pathway to the Weddell Sea birdlife, after 65 years: similarities in the species composition, richness and abundances

As part of a multi-year study of top predators in Antarctica, we conducted a seabird shipbased survey on board Almirante Irizar icebreaker in the Weddell Sea to the Filchner Ice Shelf in the austral summer 2020. We carried out 10-minute counts along 1843 km during 125 hours of observation. We analyzed the species distributions and the relationships with the ice cover. We registered 15 species of which four represented more than 85% of the total abundance: Antarctic petrel Thalassoica antarctica (43.9%), snow petrel Pagodroma nivea (16.3%), Arctic tern Sterna paradisaea (15.2%) and emperor penguin Aptenodytes forsteri (10.1%). Species distribution and its relationship with ice cover were analyzed statistically. The ice cover concentration was estimated by using satellite images. We compared our results with the first ship-based bird survey conducted up to the Filchner Ice Shelf in the austral summer 1955/56 to analyze possible changes in the bird community over time. Out of 13 recorded species in the 1955/56 cruise, 11 were present in this study with similar abundance proportions. In both cruises, the bird community consisted of a group of non-numerous species associated with icefree waters and another group of very numerous species associated with high concentrations on ice cover. The similarities between the two cruises, spaced 65 years apart, suggest a temporal persistence of the bird community of the central and the southern Weddell Sea that could be explained by the dynamics of the ice cover and the presence of reproductive colonies within the study site. The current environmental warming is alarming in this bird community because more than 85% of all its individuals belong to four species strongly dependent on ice cover.

Model Study of the Effects of Climate Change on the Methane Emissions on the Arctic Shelves

Based on a regional ice-ocean model, we simulated the state of the water masses of the Arctic Ocean to analyze the transport of dissolved methane on the Arctic shelves. From 1970 to 2019, we obtained estimates of methane emissions at the Arctic seas due to the degradation of submarine permafrost and gas release at the ocean–bottom interface. The calculated annual methane flux from the Arctic shelf seas into the atmosphere did not exceed 2 Tg CH4 year−1. We have shown that the East Siberian shelf seas make the main contribution to the total methane emissions of the region. The spatial variability of the methane fluxes into the atmosphere is primarily due to the peculiarities of the water circulation and ice conditions. Only 7% of the dissolved methane originating from sediment enters the atmosphere within the study area. Most of it appears to be transported below the surface and oxidized by microbial activity. We found that increasing periods and areas of ice-free water and decreasing ice concentration have contributed to a steady increase in methane emissions since the middle of the first decade of the current century.

Antibiotics in fish caught from ice-sealed waters: Spatial and species variations, tissue distribution, bioaccumulation, and human health risk

Antibiotics are increasingly detected in fish caught in ice-free waters, but information on fish caught in ice-sealed waters is insufficient. The concentrations of 23 antibiotics in the gills, muscles, kidneys, livers, biles, and brains of Cyprinus carpio and Hypophthalmichthys nobilis caught during winter fish-hunting activities in Chagan Lake, Haernao Reservoir, and Shitoukoumen Reservoir were systematically studied to ascertain the variations among fish species and fishing regions, tissue distribution, and bioaccumulation, as well as the potential risk to humans via the consumption of contaminated fish. The results indicated that the individual antibiotic concentration in tissues ranged from undetectable to 35.0 ng/g ww. The total antibiotic concentration in fish muscles from Shitoukoumen Reservoir was lower than that from Chagan Lake and Haernao Reservoir, but showed no significant difference between Cyprinus carpio and Hypophthalmichthys nobilis. Chloramphenicols had a high proportion in most fish tissues ranging from 28.3% to 44.0%, and the antibiotics were mainly distributed in the livers with a total concentration of 54.8 ± 9.9 ng/g ww. The mean values of bioaccumulation factors (BAF) of antibiotics in tissues ranged from 79.4 to 1000 L/kg, with the higher values found in the fish livers. The hazard quotient and hazard index value of antibiotics in the muscles of fish from ice-sealed were less than 1, indicating a negligible risk to human health via the consumption of fish muscles. This study revealed that the total antibiotic concentration in muscles showed spatial variations but not fish species-dependence. The antibiotics mainly accumulated in the livers. In addition, the target antibiotic concentrations in the muscles of fish from ice-sealed waters met the safe for consumption criteria.

Study on the protective effect of cooling the surface of frozen water on renal function in robotic-assisted laparoscopic nephrect

Objective: To compare the effects of ice water kidney cooling and traditional non-cooling surgery on postoperative renal function in robot-assisted laparoscopic partial nephrectomy, and explore its clinical value in protecting renal function. Methods: A retrospective analysis is conducted on the base of the clinical data of patients undergoing robot-assisted laparoscopic partial nephrectomy in Second Affiliated Hospital of Navy Military Medical University from January to November 2019. A total of 89 cases, of which 21 cases were treated with ice water to cool the kidney surface and block the renal artery during the operation (cooling group); 68 cases only clamp the renal artery (control group). Compare the difference of the operation time, R.E.N.A.L. score, intraoperative blood loss, renal artery block of time,postoperative intestinal recovery time, cut edge positive rate, preoperative and postoperative blood electrolyte levels, the change of blood creatinine and GFR before operation and the first and third months after the operation and other indicators between two groups. Results: All the 89 patients completed the operation normally, and no conversion to open surgery or to general endoscopic surgery. The two groups of patients had statistically significant differences in tumor diameter [7.0(5.5, 8.0) vs 3.8(3.0, 5.0) cm, P<0.001], R.E.N.A.L. score [8.0(6.5, 8.0) vs 6.0(5.0, 8.0), P=0.003], Chloride (Cl-) in the blood [(103.29±2.81) vs (104.74±2.58) mmol/L, P=0.030], (P<0.05) in the preoperative data. There were significant differences in renal artery occlusion time [20.0(18.5, 27.5) vs 19.0(15.0, 21.0) min, P=0.023] and operation time [168.0(130.0, 182.5) vs 130.0(110.0, 177.5) min, P=0.007] between the two groups (P<0.05). There was no significant difference in the blood creatinine after one or 3 month as well as for the glomerular filtration rate (all P>0.05). After follow-up for 3-24 months, no tumor recurrence or distant metastasis occurred in both groups, and no related complications caused by ice-free Water Cooling Technique in the cooling group. Conclusions: It is safe and effective to apply kidney surface cooling technique with ice water in robot-assisted laparoscopic partial nephrectomy for complex kidney tumor. It can significantly reduce the renal parenchyma warm ischemia injury of renal parenchyma. And it's conducive to the recovery of patients with postoperative renal function, which can maximize the protection of renal function of patients.

When a Year Is Not Enough: Further Study of the Seasonality of Planktonic Protist Communities Structure in an Ice-Free High Arctic Fjord (Adventfjorden, West Spitsbergen)

As a contribution to understanding the ecological framework of protistan seasonal succession patterns, we present the weekly-to-monthly (January–October) light microscopy-based study of nano- and microplanktonic protist communities of Adventfjorden waters in 2013. In general, protist dynamics corresponded to the classic paradigm for the Arctic ice-free waters with extremely low abundance and diversity in winter, with the main abundance and chlorophyll-a peak in April-May, followed by a diverse but low abundant community during summer/autumn. However, the reference of the obtained data to the previously conducted year-round research in 2012 allows us to observe substantial variability in seasonal patterns between the two consecutive years. The most striking difference concerned the spring bloom composition and abundance, with clear domination of Phaeocystis pouchetii in Atlantified fjord waters in 2012 and Bacillariophyceae-dominated (mainly Fragilariopsis, Thalassiosira nordenskioeldii, and, in a lesser extent, also Pseudo-nitzschia seriata) bloom in 2013 when local water prevailed. On the other hand, a surprisingly high share of spring bloom taxa persisted throughout the summer/autumn of 2013 when they co-occurred with typical summer taxa (dinoflagellates and other small flagellates). Their extended growth could, at least in part, result from scarce Ciliophora throughout the season, which, in turn, can be attributed to the high grazing pressure of very numerous meroplankton and mesozooplankton. In light of this, our results may be relevant in discussions proposed for the West Spitsbergen waters link between the Atlantic water inflow and the spring bloom composition, as well as its further progression in the productive season. They also highlight the strong need for further high-resolution monitoring of annual plankton cycles and great caution when looking for phenological patterns within a single year or when interpreting short-term data.

Review and comparison of existing risk analysis models applied within shipping in ice-covered waters

With the changing climate and declining extent of sea ice, the activities in the Arctic region have become increasing significantly. Compared to the environments with ice-free waters, the harsh environment in the Arctic is due to ice, low temperatures, remoteness, etc., all of which will complicate ship operations. Research on the shipping risk analysis in ice-covered waters is important because such research can improve the management of shipping businesses and aid accident prevention initiatives in the Arctic. In this paper, we systematically review and compare risk models for shipping in ice-covered waters to report experiences in the field and to identify existing knowledge gaps. This work provides a broad review and comparison of the state-of-the-art risk analysis models by considering the models’ purposes, theoretical frameworks, risk factors, and outputs, and it includes an analysis of the field-specific terminology that is used to define accidents. The results indicate that the risk analysis of the Arctic faces challenges, as a complete overview of accident data is not easy to find. There has been significantly less research done on convoy operations in ice and overtaking and meeting in an ice channel. In addition, interactions between risk factors and human factors are not sufficiently understood and thus need to be further studied. Being familiar with knowledge gaps acts as a catalyst for further research on risk analysis within shipping in Arctic conditions.

Iceberg Detection in Dual-Polarized C-Band SAR Imagery by Segmentation and Nonparametric CFAR (SnP-CFAR)

We propose an unsupervised method for iceberg detection over sea ice-free waters. The algorithm is based on the segmentation and nonparametric constant false alarm rate (SnP-CFAR) approach. Unlike in parametric CFAR detection, in our method, there is no need to define target, guard, and background areas explicitly. Instead, we apply the CFAR detection to the pixels within each detected segment and the background is formed of the nearby pixels not included in the target segment. By using nonparametric background probability density function (PDF) estimates, we also eliminate the need of assuming a specific type of a background PDF. We compared the detection results with the operational Danish Meteorological Institute (DMI) Gamma-CFAR algorithm results. The results were evaluated against icebergs manually identified by the Finnish Meteorological Institute (FMI) Ice analysts. Our method also exhibits a reduced number of false alarms. We present results of iceberg detection based on the SAR channel-cross-correlation (CCC). CCC was able to distinguish many of the true targets with a low number of false alarms. However, CCC seems to miss some of the true targets and its main use would be in confirming iceberg observations.

Distributions of Arctic and Northwest Atlantic killer whales inferred from oxygen isotopes

Killer whales (Orcinus orca) are distributed widely in all oceans, although they are most common in coastal waters of temperate and high-latitude regions. The species’ distribution has not been fully described in the northwest Atlantic (NWA), where killer whales move into seasonally ice-free waters of the eastern Canadian Arctic (ECA) and occur year-round off the coast of Newfoundland and Labrador farther south. We measured stable oxygen and carbon isotope ratios in dentine phosphate (δ18OP) and structural carbonate (δ18OSC, δ13CSC) of whole teeth and annual growth layers from killer whales that stranded in the ECA (n = 11) and NWA (n = 7). Source δ18O of marine water (δ18Omarine) at location of origin was estimated from dentine δ18OP values, and then compared with predicted isoscape values to assign individual distributions. Dentine δ18OP values were also assessed against those of other known-origin North Atlantic odontocetes for spatial reference. Most ECA and NWA killer whales had mean δ18OP and estimated δ18Omarine values consistent with 18O-depleted, high-latitude waters north of the Gulf Stream, above which a marked decrease in baseline δ18O values occurs. Several individuals, however, had relatively high values that reflected origins in 18O-enriched, low-latitude waters below this boundary. Within-tooth δ18OSC ranges on the order of 1–2‰ indicated interannual variation in distribution. Different distributions inferred from oxygen isotopes suggest there is not a single killer whale population distributed across the northwest Atlantic, and corroborate dietary and morphological differences of purported ecotypes in the region.