Search Results (25)

This work completes and updates the information about the diversity and distribution of benthic assemblages in an Antarctic fjord (South Bay, Antarctic Peninsula) 40 years after the first and only community-level study was conducted there. To determine the community changes, a photographic survey was conducted at four sites with different substrate inclinations along a bathymetric gradient of 5–20 m depth. In total, 160 photoquadrats were analyzed, resulting in a total area of 40 m². Sixty taxa represented by 12 phyla were identified, of which eight phyla corresponded to animals. The remaining species corresponded to macroalgae and benthic diatoms, both taxa presenting the highest coverages of the entire study area. The highest richness and diversity values were obtained at greater depths and at the sites with the steepest slopes. Here, we discuss the role of substrate inclination and depth in the structure of the benthic assemblages concerning possible variations in the presence and frequency of physical disturbances (e.g., ice disturbance and sedimentation). The abundances, densities, and distributions of all species found are detailed, updating the ecological data of the benthic ecosystem of this Antarctic fjord from the previously published assessment four decades ago. In a continent where rapid environmental changes are being experienced due to climate-induced processes, we discuss the first massive record of benthic diatoms in this fjord and the striking absence of the sea urchin Sterechinus neumayeri, an abundant species from previous records from the early 1980s. Full article

The interannual features of the salinity in the Chukchi Sea during the ice-free period of a year are investigated on the base of Soil Moisture Active Passive (SMAP) satellite measurements and GLORYS12v1 reanalysis data. Analysis of salinity measurements revealed two types of Bering Summer Waters (BSW) propagation: “western” and “eastern”. The first is characterized by the penetration of Pacific waters into the northwest part of the sea, as well as the propagation of BSW to 180°W and 72.5°N. During the “eastern” type, salty waters are pressed to the eastern part of the shelf. Their area decreases and the northern boundary of the BSW area shifts to 174–176°W. Areas with low salinity, ~29 psu, are observed in the western part of the sea. Our study reveals that the formation of these types is affected not only by the inflow of Pacific waters through the Bering Strait but also by the East Siberian Current (ESC). Both factors are related and lead to correlated changes in the salinity of the Chukchi Sea waters. ESC carries Arctic freshwaters from west to east and leads to a decrease in salinity in the western part of the sea. At the same time, southward ESC caused the blockage of the northward currents in the Bering Strait and a decrease in the influx of saline Pacific waters in the southern part of the Chukchi Sea. The intensification of ESC occurred in 1994, 2002, 2012, and 2016, when the volume transport of ESC increased by approximately 0.2 Sv, while the influx through the Bering Strait decreased. As a result, in the years with intense ESC, the spatial structure of the salinity of the Chukchi Sea changed significantly and the shelf-averaged salinity decreased by 0.3–0.5 psu. Full article

This paper presents a comprehensive study of winter temperatures in Norway and northern Sweden, covering a period of 50 to 70 years. The analysis utilizes Singular Spectrum Analysis (SSA) to investigate temperature trends at six selected locations. The results demonstrate an overall long-term rise in temperatures, which can be attributed to global warming. However, when investigating variations in highest, lowest, and average temperatures for December, January, and February, 50% of the cases exhibit a significant decrease in recent years, indicating colder winters, especially in December. The study also explores the variations in Atlantic Meridional Overturning Circulation (AMOC) variations as a crucial climate factor over the last 15 years, estimating a possible 20% decrease/slowdown within the first half of the 21st century. Subsequently, the study investigates potential similarities between winter AMOC and winter temperatures in the mid to high latitudes over the chosen locations. Additionally, the study examines another important climatic index, the North Atlantic Oscillation (NAO), and explores possible similarities between the winter NAO index and winter temperatures. The findings reveal a moderate observed lagged correlation for AMOC-smoothed temperatures, particularly in December, along the coastal areas of Norway. Conversely, a stronger lagged correlation is observed between the winter NAO index and temperatures in northwest Sweden and coastal areas of Norway. Thus, NAO may influence both AMOC and winter temperatures (NAO drives both AMOC and temperatures). Furthermore, the paper investigates the impact of colder winters, whether caused by AMOC, NAO, or other factors like winds or sea ice changes, on electrical power and energy systems, highlighting potential challenges such as reduced electricity generation, increased electricity consumption, and the vulnerability of power grids to winter storms. The study concludes by emphasizing the importance of enhancing the knowledge of electrical engineering researchers regarding important climate indices, AMOC and NAO, the possible associations between them and winter temperatures, and addressing the challenges posed by the likelihood of colder winters in power systems. Full article

Satellite altimeters have been used to monitor Arctic sea ice (ASI) thickness for several decades, but whether the different altimeter missions (such as radar and laser altimeters) are in agreement with each other and suitable for long-term research needs to be investigated. To analyze the spatiotemporal characteristics of ASI, continuous long-term first-year ice, and multi-year ice of ASI freeboard, thickness, and volume from 2002 to 2021 using the gridded nadirization method from Envisat, CryoSat-2, and ICESat-2, altimeter data are comprehensively constructed and assessed. The influences of sea surface temperature (SST) and sea surface wind field (SSW) on ASI are also discussed. The freeboard/thickness and extent/area of ASI all varied seasonally and reached their maximum and minimum in April and October, March and September, respectively. From 2002 to 2021, the freeboard, thickness, extent, and area of ASI all consistently showed downward trends, and sea ice volume decreased by 5437 km³/month. SST in the Arctic rose by 0.003 degrees C/month, and the sea ice changes lagged behind this temperature variation by one month between 2002 and 2021. The meridional winds blowing from the central Arctic region along the eastern coast of Greenland to the North Atlantic each month are consistent with changes in the freeboard and thickness of ASI. SST and SSW are two of the most critical factors driving sea ice changes. This study provides new data and technical support for monitoring ASI and exploring its response mechanisms to climate change. Full article

Rock glaciers are an integral part of the periglacial environment. At the regional scale in the Greater Caucasus, there have been no comprehensive systematic efforts to assess the distribution of rock glaciers, although some individual parts of ranges have been mapped before. In this study we produce the first inventory of rock glaciers from the entire Greater Caucasus region—Russia, Georgia, and Azerbaijan. A remote sensing survey was conducted using Geo-Information System (GIS) and Google Earth Pro software based on high-resolution satellite imagery—SPOT, Worldview, QuickBird, and IKONOS, based on data obtained during the period 2004–2021. Sentinel-2 imagery from the year 2020 was also used as a supplementary source. The ASTER GDEM (2011) was used to determine location, elevation, and slope for all rock glaciers. Using a manual approach to digitize rock glaciers, we discovered that the mountain range contains 1461 rock glaciers with a total area of 297.8 ± 23.0 km². Visual inspection of the morphology suggests that 1018 rock glaciers with a total area of 199.6 ± 15.9 km² (67% of the total rock glacier area) are active, while the remaining rock glaciers appear to be relict. The average maximum altitude of all rock glaciers is found at 3152 ± 96 m above sea level (a.s.l.) while the mean and minimum altitude are 3009 ± 91 m and 2882 ± 87 m a.s.l., respectively. We find that the average minimum altitude of active rock glaciers is higher (2955 ± 98 m a.s.l.) than in relict rock glaciers (2716 ± 83 m a.s.l.). No clear difference is discernible between the surface slope of active (41.4 ± 3°) and relict (38.8 ± 4°) rock glaciers in the entire mountain region. This inventory provides a database for understanding the extent of permafrost in the Greater Caucasus and is an important basis for further research of geomorphology and palaeoglaciology in this region. The inventory will be submitted to the Global Land Ice Measurements from Space (GLIMS) database and can be used for future studies. Full article

The Ku-band scatterometer called CSCAT onboard the Chinese–French Oceanography Satellite (CFOSAT) is the first spaceborne rotating fan-beam scatterometer (RFSCAT). A new algorithm for classification of Arctic sea ice types on CSCAT measurement data using a random forest classifier is presented. The random forest classifier is trained on the National Snow and Ice Data Center (NSIDC) weekly sea ice age and sea ice concentration product. Five feature parameters, including the mean value of horizontal and vertical polarization backscatter coefficient, the standard deviation of horizontal and vertical polarization backscatter coefficient and the copol ratio, are innovatively extracted from orbital measurement for the first time to distinguish water, first-year ice (FYI) and multi-year ice (MYI). The overall accuracy and kappa coefficient of sea ice type model are 93.35% and 88.53%, respectively, and the precisions of water, FYI, and MYI are 99.67%, 86.60%, and 79.74%, respectively. Multi-source datasets, including daily sea ice type from the EUMETSAT Ocean and Sea Ice Satellite Application Facility (OSI SAF), NSIDC weekly sea ice age, multi-year ice concentration (MYIC) provided by the University of Bremen, and SAR-based sea ice type released by Copernicus Marine Environment Monitoring Service (CMEMS) have been used for comparison and validation. It is shown that the most obvious difference in the distribution of sea ice types between the CSCAT results and OSI SAF sea ice type are mainly concentrated in the marginal zones of FYI and MYI. Furthermore, compared with OSI SAF sea ice type, the area of MYI derived from CSCAT is more homogeneous with less noise, especially in the case of younger multiyear ice. In the East Greenland region, CSCAT identifies more pixels as MYI with lower MYIC values, showing better accuracy in the identification of areas with obvious mobility of MYI. In conclusion, this research verifies the capability of CSCAT in monitoring Arctic sea ice classification, especially in the spatial homogeneity and detectable duration of sea ice classification. Given the high accuracy and processing speed, the random forest-based algorithm can offer good guidance for sea ice classification with FY-3E/RFSCAT, i.e., a dual-frequency (Ku and C band) scatterometer called WindRAD. Full article

In August 2020, during a dramatical summer retreat of sea ice in the Nansen Basin, a study of phytoplankton was conducted on the transect from two northern stations in the marginal ice zone (MIZ) (north of 83° N m and east of 38° E) through the open water to the southern station located in the Franz Victoria Trench. The presence of melted polar surface waters (mPSW), polar surface waters (PSW), and Atlantic waters (AW) were characteristic of the MIZ. There are only two water masses in open water, namely PSW and AW, at the southernmost station; the contribution of AW was minimal. In the MIZ, first-year and multiyear ice species and Atlantic species were noted; Atlantic species and first-year ice species were in open water, and only ice flora was at the southernmost station. The maximum phytoplankton biomass (30 g · m⁻³) was recorded at the northernmost station of the MIZ, and 99% of the phytoplankton consisted of a large diatom Porosira glacialis. Intensive growth of this species occurred on the subsurface halocline separating mPSW from PSW. A thermocline was formed in open water south of the MIZ towards the Franz Victoria Trench. A strong stratification decreases vertical nutrient fluxes, so phytoplankton biomass decreases significantly. Phytoplankton formed the maximum biomass in the thermocline. When moving south, biomass decreased and its minimum values were observed at the southernmost station where the influence of AW is minimal or completely absent. A transition from the silicon-limited state of phytoplankton (MIZ area) to nitrogen-limited (open water) was noted. Full article

A blocking high in the Ural Mountains, which is recognized as the third major blocking high area in the northern hemisphere, describes a deep warm high-pressure system superimposed on the westerly belt. Based on the ERA-5 daily reanalysis data (the fifth-generation European Centre for Medium-Range Weather Forecasts atmospheric reanalysis global climate dataset) and using the Tibaldi and Molteni (TM) method, we selected 43 blocking high events in the Ural Mountains during the extended winters of 1979–2020 and analyzed their atmospheric circulation characteristics and influencing factors. Our findings revealed a downward trend in the frequency of occurrence of blocking highs in the Ural Mountains in winter, most of them were short-lived; furthermore, the frequency and duration of these occurrences generally followed a 3–4 years oscillating cycle. The synthetic results of the geopotential height (HGT) anomaly field and the surface air temperature (SAT) anomaly field of these 43 extended wintertime blocking high events in the Ural Mountains region showed that during the development of a blocking high, the central intensity of the positive anomalies in the Ural Mountains region first increased and then weakened, while the central intensity and meridional span of the negative anomalies in the Eurasian mid-latitudes of the SAT anomaly field increased continuously. In addition, abnormally high sea surface temperature (SST) in the North Atlantic sea area and abnormal reduction of sea ice (SI) in the Barents-Kara Sea and the Chukchi Sea in autumn had a significant impact on the wintertime formation of Ural Mountains blocking highs. In contrast, in autumn, the abnormal reduction of SI in the Barents-Kara and Chukchi Seas might also have led to the westward positioning of Ural Mountains blocking highs. Full article

The surface effective emissivities of Arctic sea ice are calculated using Advanced Microwave Scanning Radiometer 2 (AMSR2) measurements. These emissivities are analyzed for stable winter conditions during the months of January–May and November and December of 2020 for several main sea ice types defined with the sea ice maps of the Arctic and Antarctic Research Institute (AARI). The sea ice emissivities are derived from the AMSR2 data using the radiation transfer model for a non-scattering atmosphere and ERA5 reanalysis data. The emissivities are analyzed only for areas of totally consolidated sea ice of definite types. Probability distribution functions are built for the emissivities and their functions for such sea ice types as nilas, young ice, thin first-year (FY) ice, medium FY ice, thick FY ice and multi-year ice. The emissivity variations with frequency are estimated for each of the considered sea ice type for all seven months. The variations are calculated both for the emissivities and for their gradients at the AMSR2 channel frequencies. Obtained emissivities turned out to be generally lower than reported previously in scientific studies, whereas the emissivity variability values proved to be much larger than was known before. For all FY ice types, at all the frequencies, an increase in the emissivity at the beginning of winter and its decrease by the end of May are observed. The emissivity gradients demonstrate noticeable decreases with sea ice age, and their values may be used in sea ice classification algorithms based on the AMSR2 data. Full article

The East Siberian Arctic shelf is the area where the largest natural gas reserves are concentrated. The formation of permafrost of the Arctic shelf during the Ice Age contributed to the emergence of a zone of stable existence of gas hydrates in the sedimentary layer, and subsequent flooding of the shelf led to its gradual degradation, the thawing of gas hydrates and the subsequent emissions of methane into the atmosphere. In the first part of the paper, we use mathematical modeling to study the processes of the formation of subsea permafrost on the Arctic shelf considering changes in the sea levels over the past 200 thousand years. Numerical simulations show the influence of climate warming up to 2200 on the degradation of subsea permafrost and the violation of the conditions for the stable existence of methane hydrates in bottom sediments using the example of the East Siberian shelf. The second part of the paper proposes a method for seismic monitoring of the state of gas hydrates based on a solution of multi-parameter inverse seismic problems. In particular, the degree of attenuation of seismic energy is one of the objective parameters for assessing the consolidation of gas hydrates: the closer they are to the beginning of decomposition, the higher the attenuation and, hence, the lower the quality factor. In this publication, we do not solve a multi-parameter inverse seismic problem for a real geological object. This would be impossible due to the lack of necessary data. Instead, we focus on substantiating the possibility of correct solutions for the problem of the reconstruction of the absorption and velocities for a viscoelastic medium in relation to the problem of monitoring the state of gas hydrate deposits. As noted in a range of publications, the thawing of gas hydrates leads to an increase in the fluid saturation of the geological medium followed by an increase in the absorption of seismic energy—that is, a decrease in the quality factor. Thus, the methods of seismic monitoring of the state of gas hydrates to predict the possibility of developing dangerous scenarios should be based on solving a multi-parameter inverse seismic problem. This publication is devoted to the presentation of this approach. Full article

During the next century, the Ross Sea is expected to reduce summer sea ice concentrations and consolidate the presence of shallower mixed layers. Those changes may have a potentially catastrophic effect on the zooplankton community. To investigate if Ross Sea’s past physical and biological condition changes have affected the tintinnids population, and to understand future tintinnids’ role in the plankton community, seawater samples collected in the Terra Nova Bay polynya area during eleven summer expeditions from 1988 to 2017 were analyzed. During this time period, tintinnids’ abundance ranged from 0 to a maximum of 4980 indL⁻¹. The most representative species were Cymatocylis drygalskii, Codonellopsis gaussi and Laackmanniella naviculifaera. These species can be considered keystone species and they can be used to monitor the long-term evolution of the whole microzooplankton community in Terra Nova Bay polynya. The tintinnids’ abundance presented minimum values in 2001 after which there has been a significant increase in the most recent years. The increase in tintinnids’ abundance showed a positive correlation with the temperature, while salinity did not indicate any relationship. In particular, the majority of genera detected showed a significant temperature correlation, with the only exception of Amphorides genus, recorded for the first time in the study area. Our results provide new insights into the spatial distribution and structure of the Antarctic tintinnids community. Full article

Recent observations and publications have presented the possibility of a high and accelerated sea-level rise (SLR) later this century due to ice sheet instability and retreat in Antarctica. Under a high warming scenario, this may result in a sea level in 2100 that is up to 2 m higher than present and 5 m in 2150. The large uncertainties in these projections significantly increase the challenge for investment planning in coastal strategies in densely populated coastal zones such as the Netherlands. In this paper, we present the results of two studies that were carried out within the framework of the Dutch Delta Programme. The first study showed that it is not only the absolute SLR that presents a challenge but also the annual rate of rise. The latter impacts the lifetime of constructions such as barriers and pumping stations. When the rate of sea-level rise increases up to several centimeters per year, the intended lifetime of a flood defense structure may be reduced from a century to several decades. This new challenge requires new technologies, experiments, strategies, and governance. The second study explored different strategies for the long term to adapt to high SLR (>1 m) and assessed the consequences thereof on adaptation and developments in the coming 2–3 decades. We believe that strategic choices have to be made regarding the permanent closure of estuaries, the pumping or periodic storage of high river discharges, agriculture in an increasingly saline coastal area, and the maintenance of the coastline by beach nourishments. These strategic choices have to be complemented by no-regret measures such as spatial reservations for future sand extraction (for beach nourishments) and future expansion of flood defenses, water discharge, and water storage. In addition, it is advised to include flexibility in the design of new infrastructure. Full article

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. Full article

The European Organisation for the Exploitation of Meteorological Satellites-Ocean and Sea Ice Satellite Application Facility–European Space Agency-Climate Change Initiative (EUMETSAT-OSISAF–ESA-CCI) Level-4 sea-ice concentration (SIC) climate data records (CDRs), named SICCI-25km, SICCI-50km and OSI-450, provide gridded SIC error estimates in addition to SIC. These error estimates, called total error henceforth, comprise a random, uncorrelated error contribution from retrieval and sensor noise, aka the algorithm standard error, and a locally-to-regionally correlated contribution from gridding and averaging Level-2 SIC into the Level-4 SIC CDRs, aka the representativity error. However, these CDRs do not yet provide an error covariance matrix. Therefore, correlation scales of these error contributions and the total error in particular are unknown. In addition, larger-scale SIC errors due to, e.g., unaccounted weather influence or mismatch between the actual ice type and the algorithm setup are neither well represented by the total error, nor are their correlation scales known for these CDRs. In this study, I attempt to contribute to filling this knowledge gap by deriving spatial correlation length scales for the total error and the large-scale SIC error for high-concentration pack ice. For every grid cell with >90% SIC, I derive circular one-point correlation maps of 1000 km radius by computing the cross-correlation between the central 31-day time series of the errors and all other 31-day error time series within that circular area (disc) with 1000 km radius. I approximate the observed decrease in the correlation away from the disc’s center with an exponential function that best fits this decrease and thereby obtain the correlation length scale L sought. With this approach, I derive L separately for the total error and the large-scale SIC error for every high-concentration grid cell, and map, present and discuss these for the Arctic and the Southern Ocean for the year 2010 for the above-mentioned products. I find correlation length scales are substantially smaller for the total error, mostly below ~200 km, than the SIC error, ~200 km to ~700 km, in both hemispheres. I observe considerable spatiotemporal variability of the SIC error correlation length scales in both hemispheres and provide first directions to explain these. For SICCI-50km, I present the first evidence of the method’s robustness for other years and time series of L for 2003–2010. Full article

Climate warming has enabled the Arctic region to achieve seasonal navigation, and sea ice concentration is an important factor affecting the navigation of the Arctic waterways. This article uses the Arctic sea ice concentration data of the three highest temperatures in 2016, 2019, and 2020, combined with the Arctic summer sea level pressure, wind field, temperature, temperature anomaly, ice age, and sea ice movement data to analyze the spatial and temporal variation of sea ice and connectivity in the Northeast Passage (NEP) of the Arctic in Summer in three hot years, and summarizes the causes of sea ice anomalies. The results show that: (1) the summer Arctic sea ice extent in 2016, 2019 and 2020 were all lower than the multi-year average sea ice extent, and the summer sea ice extent in 2020 had the largest change trend; (2) in October of these three years, the sea ice was all negative anomalies, extending the opening time of the NEP; (3) when the sea ice concentration was 30% as the threshold, the navigation period of the NEP in 2016 was from mid-August to late October, 2019 was from the beginning of August to mid-October, 2020 was from the end of July to the end of October, and 2020 was the longest year since the opening of the NEP; (4) when the sea ice concentration was 10% as the threshold, the navigation period of the NEP in 2016 was from the end of August to the end of October, 2019 was from early August to mid-October, and 2020 was from the beginning of August to the end of October; (5) the key navigable areas of the NEP in the past three years were the central waters of the East Siberian Sea, the New Siberian Islands and the Vilkitsky Strait; (6) the navigation period of the NEP in 2016, 2019 and 2020 was longer. The main reasons were that the temperature of the NEP in the past 3 years was relatively high, the wind was weak, the sea ice movement had little effect, and the sea ice age in the key navigable areas was first year ice, which was easy to melt, which greatly promoted the opening of the NEP. Full article