Search Results (65)

Ground-surface temperature (GST) in maritime Antarctic ice-free areas is influenced by atmospheric forcing, snow cover, surface energy and topography. Previous PERMATHERMAL studies in Livingston and Deception Islands have shown changes in air and ground-surface thermal regimes, with fewer cold conditions, greater thawing influence and strong snow-cover modulation. However, the interval in which GST responds effectively to radiative and topographic forcing remains poorly explored. We characterize the station- and season-specific timing of the thermally effective GST thawing period and evaluate topographic and modeled potential controls on its thermal intensity and cumulative effect around the Spanish Antarctic Station Juan Carlos I, Hurd Peninsula, Livingston Island. Onset and end were objectively delimited by using three consecutive days with daily mean GST > 0.5 °C and daily thermal amplitude > 1.0 °C. Hourly GST records from six PERMATHERMAL stations were combined with potential radiation, potential insolation and topographic variables derived from a high-resolution UAV-based DEM. Accumulated thawing degree days were strongly influenced by period duration. Mean thermal intensity was primarily associated with elevation, while mean modeled potential radiation provided additional explanatory power only when combined with elevation. This UAV–GIS–GST approach provides a simple framework for assessing local surface–atmosphere coupling in remote Antarctic ice-free areas. Full article

Rapid Atlantification is altering primary productivity and benthic-pelagic coupling in the Eurasian Arctic. This study assessed sedimentary pigments as indicators of exported production in the poorly studied St. Anna Trough, a critical conduit between the Barents and Kara seas. Sediment samples were collected at 20 stations in autumn 2023, and phytopigment concentrations were analyzed spectrophotometrically alongside hydrological data. Multivariate analysis revealed two distinct benthic regimes separated by the Marginal Ice Frontal Zone. The southern sector, influenced by thick seasonal warm water masses (WWM) in the subsurface layer, exhibited mesotrophic conditions with mean chlorophyll-a + pheophytin-a concentrations of 30.28 ± 6.51 µg g⁻¹. The northern sector, dominated by Arctic-origin water masses, was oligotrophic (4.45 ± 0.54 µg g⁻¹). Redundancy analysis identified WWM thickness as the primary driver, explaining 60.5% of the total variance in pigment contents, followed by ice-cover duration (9.8% negative effect). Pigment indices and high pheophytin proportions indicated predominantly detrital organic matter, though stations near the Barents Sea inflow showed fresher material. The prevalence of chlorophyll-b in the north suggested ice-associated green algae, while chlorophyll-c dominated the diatom-rich southern inflow. These findings establish a crucial baseline for monitoring climate-driven shifts in pelagic-benthic coupling as sea ice retreat continues. Full article

Surge-like glacier instabilities in Central Asia remain underexplored, particularly in regions of mild instability or smaller glaciers. In 1980, two leading Soviet glaciologists proposed a classification method (GS1980) to calculate the spatial distribution of “pulsating” glaciers in the Hissar–Alay range, predicting a 20% prevalence of unstable flow and claiming highly accurate detection. These findings were unconfirmed in subsequent studies, which typically reported fewer than 10 surge-type glaciers in the region. Here, we address this discrepancy by reassessing the GS1980 predictions using a newly compiled multi-sensor satellite dataset covering nearly six decades. We systematically examine glacier dynamics in the region, assessing ice flow instabilities from changes in terminus position, ice thickness, and surface morphology. We identify 171 glaciers that exhibit pulsating behavior, corresponding to 25% of the sample—in broad agreement with GS1980. Flow instabilities tend to be modest in scale, with slow advances and long active phases (mean duration of 14 years). We find that the GS1980 model shows some ability to distinguish pulsating from stable-flowing glaciers; however, its predictive power is lower than claimed due to the simplifying assumptions of its morphology-based approach and the uncertainties in the input data. Our results indicate that pulsations in the region are more widespread than previously reported, but fall at the weaker end of the spectrum of glacier instability, which may not be well represented by a sharp binary classification (surge-type versus stable). As more detailed satellite records become available, we suggest that a more nuanced framework may be useful to recognize and interpret subtler instabilities of small glaciers. Full article

NavIC and GPS are satellite-based navigation systems developed by India and the United States, respectively, and are widely used for ionospheric and space weather studies. This paper presents a comparative analysis of NavIC- and GPS-derived total electron content (TEC) during a High-Intensity Long-Duration Continuous AE Activity (HILDCAA) event that occurred from 17 to 21 August 2017. The analysis covers the five days of the event, along with three days before and after, using observations from a single low-latitude station over the Indian region. NavIC performance is evaluated by comparing vertical TEC (vTEC) derived from dual-frequency pseudorange measurements with co-located GPS-derived vTEC. The results show a strong linear correspondence between the two datasets, with Pearson correlation coefficients exceeding ∼0.97 throughout the event interval. Such high correlation is physically expected, as the dominant contribution to TEC arises from the common vertical ionospheric column sampled by both systems. Nevertheless, the close agreement observed under sustained geomagnetic disturbance conditions demonstrates that NavIC is capable of consistently capturing ionospheric TEC variability during this specific HILDCAA event. Full article

Ice-shedding on overhead transmission lines can easily lead to jump discharge and subsequent line tripping, and effective monitoring methods are still lacking. To address this problem, this study proposes a distributed optical fiber sensing approach based on Brillouin optical time-domain reflectometry (BOTDR) for detecting ice-shedding discharge on 110 kV conductor–ground wire. The optical fibers embedded in an optical fiber composite overhead ground wire (OPGW) are used as sensing elements. Through simulated ice-shedding discharge experiments under different icing conditions, the Brillouin frequency shift (BFS) characteristics along the OPGW fiber are investigated, and the relationship between the BFS increment caused by the discharge-induced temperature rise and the discharge parameters is revealed. The experimental results show that ice-shedding discharge produces a localized temperature-rise region in the OPGW fiber, with an axial extent of 20–40 cm and a duration of 2–4 s. The maximum BFS increment due to the discharge temperature rise, Δv_Tm, is strongly dependent on the icing condition. Under conditions of no icing, light rime, and glaze ice on the conductor only, Δv_Tm remains within 5.43–7.94 MHz, whereas when both the conductor and ground wire are covered with glaze ice, Δv_Tm decreases significantly to 2.91–3.76 MHz. Further analysis indicates that, to satisfy the requirements for detecting ice-shedding discharge, the BOTDR must achieve a spatial resolution better than 0.1 m and a temporal sampling rate of no less than 5 Hz. These findings verify the feasibility of using distributed optical fiber sensing technology to detect ice-shedding discharge and provide experimental support for studies on the associated discharge mechanisms. Full article

Seasonal temperature reconstructions provide a critical approach for reconciling discrepancies between paleoclimate model simulations and proxy records. However, cold-season temperature variations remain poorly constrained due to the scarcity of robust cold-season temperature proxies. This study provides critical insights into lake ice-covered season temperature dynamics in Northeast China, a region where cold-season climate variability has remained poorly constrained in paleoclimate reconstructions. We collected total organic carbon sequences from seven closed lakes in Northeast China over the last 10,000 years to evaluate the lake ice cover duration as a proxy for lake ice-covered season temperature during the early–middle Holocene. Our results show that the lake ice cover duration decreased from ~8 ka BP, reaching a minimum at around 4 ka BP. This pattern is linked to ice-covered season temperature changes, with warmer ice-covered seasons leading to shorter ice cover durations and increased lake productivity, which were driven by orbital forcing (seasonal insolation changes) and greenhouse gas concentrations. Orbital forcing played a dominant role in winter warming between 8 and 4 ka BP, while greenhouse gas also contributed, but to a lesser extent. Full article

Global warming reduces the thickness and duration of seasonal lake ice, increasing the risk of ice cover failure. To investigate the bending behavior of ice cover, six groups of full-scale cantilever beam tests were conducted on a brackish water lake during the winter of 2023–2024, covering the following three ice periods: growth, stable, and melt. A total of 16 upward-loaded beams and 24 downward-loaded beams were tested. The results showed that the flexural strength of brackish ice was 374.21 ± 99.93 kPa, and the effective elastic modulus was 2.77 ± 0.93 GPa. The square root of bulk porosity, fitted with an exponential function, is the optimal predictor of flexural performance. Both flexural strength and effective elastic modulus systematically decreased with increasing porosity, and empirical regression formulas were established. On average, downward-loaded flexural strength was approximately 17.3% to 38.8% higher than upward-loaded strength, whereas elastic modulus showed no significant difference between the two loading directions. Flexural mechanical properties during the melt period reduced significantly, with a strength and modulus about 33.0% to 61.1% lower than those in the growth and stable periods. Comparisons with existing datasets demonstrate that the mechanical properties of brackish ice are lower than those of freshwater ice but higher than those of sea ice. This study provides new in situ data on the full-scale flexural mechanical properties of brackish ice and offers an important basis for assessing ice loads in lakes and estuarine environments under climate change. Full article

This study updates the climatology of lake-effect (LE) snowfall over Lake Champlain by analyzing radar and surface data from nine winter seasons spanning 2015 to 2024. A filtering approach was applied to isolate periods with favorable LE conditions, and events were manually classified using criteria consistent with a previous climatology from 1997 to 2006. A total of 64 LE events were identified and compared across the two periods to evaluate potential changes associated with regional warming. Despite a substantial reduction in lake ice cover during the recent decades, no increase in LE frequency or duration was observed. Instead, warming has shifted the seasonal distribution of events, with fewer early-season cases and more late-season occurrences. LE events also exhibited shorter durations and higher minimum temperatures and dew points. These findings suggest that warming may constrain LE snowfall development over small lakes such as Champlain, in contrast to intensification trends reported for larger lake systems. The analysis also highlights a rarely documented transitional band type that migrated along the lake axis during synoptic shifts. Results underscore the value of observational climatologies for detecting emerging snowfall behaviors in response to climate variability. Full article

The phenomenon of surface freezing in lakes, rivers, and reservoirs, has been an essential part of Poland’s winter landscape for centuries. It plays critical ecological roles, such as regulating heat balance and influencing the state of biocenoses. Due to progressive climate warming, we have observed significant changes in ice cover duration, thickness, and timing in recent decades. Ice phenomena on rivers are temporary. They strongly depend on air temperature, which has recently been increasing worldwide. This paper analyzes the variability of ice phenomena formation in selected river profiles of the central Vistula River catchment, central Poland. The research period covers the years 1968–2016. The data come from the Institute of Meteorology and Water Management-State Research Institute (IMGW-PIB). The duration (including the dates of occurrence and disappearance of the phenomenon) and the frequency of occurrence of ice phenomena over the long-term were determined with particular attention to ice cover. The long-term occurrence of ice phenomena shows a decreasing trend (shorter duration, later onset dates) with a simultaneous increase in the average air temperature during the winter half of the hydrological year. Full article

Lake ice has a major impact on the functioning of lake ecosystems, the thermal and gas regimes of lakes, habitat conditions, socio-economic aspects of human life, local climate, etc. The multifaceted influence of lake ice makes it important to study its changes associated with global warming, including lake ice phenology, ice thickness, and the snow–ice fraction. This article presents a study of lake ice changes in different regions of Eurasia: the Arctic (Lake Imandra in the Murmansk region and Lake Kilpisjärvi in Finland), the temperate zone (six small and medium lakes in Karelia, Mozhaysk Reservoir in the Moscow region, and Lake Pääjärvi in Finland), the arid zone (Lake Ulansuhai in China), and the highlands (lakes Arpi and Sevan in Armenia). In the study regions, a statistically significant increase in winter air temperature has been recorded over the past few decades. The number of days with thaw (air temperature above 0 °C) has increased, while the number of days with severe frost (air temperature below −10 °C and −20 °C) has decreased. The share of liquid or mixed precipitation in winter increases most rapidly in the temperate zone. For two Finnish lakes, lakes Vendyurskoe and Vedlozero in Karelia, and Mozhaysk Reservoir, a decrease in the duration of the ice period was revealed, with later ice-on and earlier ice-off. The most dramatic change occurred in the large high-mountain Lake Sevan, where the water area has no longer been completely covered with ice every winter. In contrast, the small high-mountain Lake Arpi showed no significant changes in ice phenology over a 50-year period. Changes in the ice composition with an increase in the proportion of white ice and a decrease in the proportion of black ice have occurred in some lakes. In the temperate lakes Pääjärvi and Vendyurskoe, inverse dependences of the thickness of black ice on the number of days with thaw and frost in December–March for the first lake and on the amount of precipitation in the first month of ice for the second were observed. In the arid study region of China, due to the very little winter precipitation (usually less than 10 mm) only black ice occurs, and significant interannual variability in its thickness has been identified. Full article

Lake ice phenology serves as a sensitive indicator of climate change in the lake-rich Northeast China. In this study, the freeze-up date (FUD), break-up date (BUD), and ice cover duration (ICD) of 31 lakes were extracted from a time series of the land water surface temperature (LWST) derived from the combined MOD11A1 and MYD11A1 products for the hydrological years 2001 to 2021. Our analysis showed a high correlation between the ice phenology measures derived by our study and those provided by hydrological records (R² of 0.89) and public datasets (R² > 0.7). There was a notable coherence in lake ice phenology in Northeast China, with a trend in later freeze-up (0.21 days/year) and earlier break-up (0.19 days/year) dates, resulting in shorter ice cover duration (0.50 days/year). The lake ice phenology of freshwater lakes exhibited a faster rate of change compared to saltwater lakes during the period from HY2001 to HY2020. We used redundancy analysis and correlation analysis to study the relationships between the LWST and lake ice phenology with various influencing factors, including lake properties, local climate factors, and atmospheric circulation. Solar radiation, latitude, and air temperature were found to be the primary factors. The FUD was more closely related to lake characteristics, while the BUD was linked to local climate factors. The large-scale oscillations were found to influence the changes in lake ice phenology via the coupled influence of air temperature and precipitation. The Antarctic Oscillation and North Atlantic Oscillation correlate more with LWST in winter, and the Arctic Oscillation correlates more with the ICD. Full article

The presence of ice cover on temperate lakes is a crucial factor in determining the functioning of these ecosystems. The isolation of water from atmospheric influences significantly alters physical, chemical, and biological processes, and the intensity of this impact depends on the duration of the ice cover. This study analyzed the basic parameters of ice cover on several dozen lakes in Northeastern Poland. The aim of this study is to investigate the influence of morphometric parameters, alongside environmental factors, on the variation of ice cover characteristics in lakes located within the Eastern Baltic Lakeland. Characterization of ice conditions in the analyzed lakes was based on basic statistics such as minimum and maximum values, mean, standard deviation, coefficients of variation, skewness, and kurtosis. Given that the dataset contains variables describing ice phenomena in the studied lakes and data describing location, morphometric parameters, and land cover directly adjacent to the lake (treated as independent variables), a method of Spearman’s rank correlations and constrained ordination method were decided upon. Despite the relatively small study area, significant variability was observed, with average differences as follows: 26 days for the onset of ice cover, 17 days for the end date, 15 cm for ice thickness, and a 30-day difference in the average duration of ice cover. Key factors included parameters such as lake volume, average depth, and land use (urbanized and agricultural areas). Understanding parameters such as the onset and end of ice cover is essential for lake ecosystems, both from an ecological and economic perspective. This knowledge is crucial for interpreting the behavior of living organisms, water quality, and economic considerations. Full article

A machine learning model for prediction of icing on vessels and offshore structures, Spice, was recently developed by Deshpande 2023. Some variables required for the prediction of icing rates in most prediction models, including Spice, such as the spray flux, cannot be easily measured. Existing models estimate these using empirical formulations that have been heavily criticized. Most existing models are also incapable of providing the distribution of icing on the structure. The current study demonstrates a method to estimate the local wind speeds, along with spray duration, spray period, and spray flux at different locations on the surface of a moving vessel. These, along with other easily measurable values of air temperature, water temperature, and salinity, are used to predict the icing rates. The result is a model, dubbed Spice2—an upgrade of the existing Spice model—that is able to provide the icing rates and the distribution of icing on the surface of vessels and other offshore structures. The model was demonstrated with a case study of a totally enclosed lifeboat where icing rates were predicted at different locations on its surface. Successful implementation of a two-phase simulation with a coupled wind–wave domain and a moving vessel was demonstrated. Research into simplification of the currently computationally expensive method is suggested. Validation of the proposed Spice2 model against a full-scale measurement is covered in part 2 of the study. Full article

This research studies the characteristics of snow-covered area (SCA) from two vastly different sensors: optical (Moderate-Resolution Imaging Spectroradiometer, or MODIS, equipped on board the Terra satellite) and radar (Synthetic Aperture Radar (SAR) on-board Sentinel-1 satellites). The focus are the five mountain ranges of the Iberian Peninsula (Cantabrian System, Central System, Iberian Range, Pyrenees, and Sierra Nevada). The MODIS product was selected to identify SCA dynamics in these ranges using the Probability of Snow Cover Presence Index (PSCPI). In addition, we evaluate the potential advantage of the use of SAR remote sensing to complete optical SCA under cloudy conditions. For this purpose, we utilize the Copernicus High-Resolution Snow and Ice SAR Wet Snow (HRS&I SWS) product. The Pyrenees and the Sierra Nevada showed longer-lasting SCA duration and a higher PSCPI throughout the average year. Moreover, we demonstrate that the latitude gradient has a significant influence on the snowline elevation in the Iberian mountains (R² ≥ 0.84). In the Iberian mountains, a general negative SCA trend is observed due to the recent climate change impacts, with a particularly pronounced decline in the winter months (December and January). Finally, in the Pyrenees, we found that wet snow detection has high potential for the spatial gap-filling of MODIS SCA in spring, contributing above 27% to the total SCA. Notably, the additional SCA provided in winter is also significant. Based on the results obtained in the Pyrenees, we can conclude that implementing techniques that combine SAR and optical satellite sensors for SCA detection may provide valuable additional SCA data for the other Iberian mountains, in which the radar product is not available. Full article

Most deep-sea organisms feed on the organic matter produced in surface waters and settle on the seafloor. In polar regions, sea ice algal detritus and phytoplankton detritus are the main food sources for benthic fauna that reach the seafloor in pulses. Climate change affects the extension and duration of sea ice cover, which may affect the quantity and quality of food reaching the seafloor, resulting in less ice algae and more phytoplankton biomass. We conducted onboard pulse-chase experiments using sediment cores collected from Baffin Bay, Amundsen Gulf, and the Beaufort Sea to study how macroinfaunal communities in the Canadian Arctic use both food sources. Dual-labeled (¹³C and ¹⁵N) diatoms, Thalassiosira nordenskioeldii (phytoplankton treatment) and Synedra hyperborea (ice algae treatment), were used as tracers of food consumption by macroinfaunal groups. Community structure was analyzed in each region and differences were found among sites. The total uptake of both food sources was higher in Baffin Bay; the macroinfaunal biomass was the highest, with facultative filter/surface-deposit feeders accounting for more than 70% of the total biomass. The Baffin Bay station was the only location where there were notable variations in the biomass-specific uptake of ice algae and phytoplankton detritus by the bivalves and polychaetes, as well as by the community as a whole. At the same time, both food sources were consumed in equal quantities at the Amundsen Gulf and Beaufort Sea stations. This suggests that ice algae are not preferentially uptaken, and macroinfaunal communities may be resilient to a decrease in ice algal input to the seafloor inflicted by sea ice reduction. Full article