Ice Deposits Research Articles

Stable water isotope signals in tropical ice clouds in the West African monsoon simulated with a regional convection-permitting model

Abstract. Tropical ice clouds have an important influence on the Earth's radiative balance. They often form as a result of tropical deep convection, which strongly affects the water budget of the tropical tropopause layer. Ice cloud formation involves complex interactions on various scales. These processes are not yet fully understood and lead to large uncertainties in climate projections. In this study, we investigate the formation of tropical ice clouds related to deep convection in the West African monsoon, using stable water isotopes as tracers of moist atmospheric processes. We perform convection-permitting simulations with the regional Consortium for Small-Scale Modelling isotope-enabled (COSMOiso) model for the period from June to July 2016. First, we evaluate our model simulations using space-borne observations of mid-tropospheric water vapour isotopes, monthly station data of precipitation isotopes, and satellite-based precipitation estimates. Next, we explore the isotope signatures of tropical deep convection in atmospheric water vapour and ice based on a case study of a mesoscale convective system (MCS) and a statistical analysis of a 1-month period. The following five key processes related to tropical ice clouds can be distinguished based on isotope information: (1) convective lofting of enriched ice into the upper troposphere, (2) cirrus clouds that form in situ from ambient vapour under equilibrium fractionation, (3) sedimentation and sublimation of ice in the mixed-phase cloud layer in the vicinity of convective systems and underneath cirrus shields, (4) sublimation of ice in convective downdraughts that enriches the environmental vapour, and (5) the freezing of liquid water just above the 0 ∘C isotherm in convective updraughts. Importantly, we note large variations in the isotopic composition of water vapour in the upper troposphere and lower tropical tropopause layer, ranging from below −800 ‰ to over −400 ‰, which are strongly related to vertical motion and the moist processes that take place in convective updraughts and downdraughts. In convective updraughts, the vapour is depleted by the preferential condensation and deposition of heavy isotopes, whereas the non-fractionating sublimation of ice in convective downdraughts enriches the environmental vapour. An opposite vapour isotope signature emerges in thin-cirrus cloud regions where the direct transport of enriched (depleted) vapour prevails in large-scale ascent (descent). Overall, this study demonstrates that isotopes can serve as useful tracers to disentangle the role of different processes in the West African monsoon water cycle, including convective transport, the formation of ice clouds, and their impact on the tropical tropopause layer.

Multi-centennial mass balance of perennial ice deposits in Alpine caves mirrors the evolution of glaciers during the Late Holocene

Mid-latitude alpine caves preserve a record of past solid precipitation during winter, locally spanning several centuries to millennia. Dating organic macro-remains trapped in ice layers allows the determination of timing and duration of past periods of positive and negative ice mass balance. We present here the largest comparative study of ice cave sites yet published, using Bayesian age-modelling on a database comprising 107 radiocarbon dates, spread over eight caves in the Austrian Alps. We show that periods of positive mass balance coincide with past glacier advances. We find organic and macro-remain rich layers dated to the Medieval Climate Anomaly (between 850 and 1200 CE) marking widespread ice retreat. We demonstrate positive ice mass balance at all studied sites for the Little Ice Age, coinciding with the largest glacier advances in the Holocene between 1400 and 1850 CE. At the sites with records spanning over 2000 years, positive mass balance is also observed during the periods from 300 BCE to 100 CE and 600–800 CE. These subterranean ice deposits show widespread evidence of accelerated negative mass balances in recent years and their record is under imminent threat of disappearing.

Numerical simulations of radar echoes rule out basal CO2 ice deposits at Ultimi Scopuli, Mars

The principal objective of the radar sounder MARSIS experiment is to look for ice and water in the Martian subsurface. One particular focus of investigations, since 2005, has been the search for basal liquid water in the south polar layered deposits (SPLD). Anomalously strong basal echoes detected from four distinct areas at the base of the deposits at Ultimi Scopuli have been interpreted to indicate the presence of bodies of liquid water in this location, beneath a 1.5 km thick cover of ice and dust. Other explanations for the bright basal reflections have been proposed, however, including the possibility of constructive interference in layered media. Here, we test this mechanism through simulations of MARSIS radar signals propagating in models of CO2-H2O ice sequences. We then compare the results to real MARSIS data acquired over Ultimi Scopuli, finding that no CO2-H2O ice model sequence reproduces the set of real data. The results of our work have implications in relation to the global CO2 inventory of Mars.

The Impacts of Immersion Ice Nucleation Parameterizations on Arctic Mixed-Phase Stratiform Cloud Properties and the Arctic Radiation Budget in GEOS-5

Abstract The influence of four different immersion freezing parameterizations on Arctic clouds and the top-of-the atmosphere (TOA) and surface radiation fluxes is investigated in the fifth version of the National Aeronautics and Space Administration (NASA) Goddard Earth Observing System (GEOS-5) with sea surface temperature, sea ice fraction, and aerosol emissions held fixed. The different parameterizations were derived from a variety of sources, including classical nucleation theory and field and laboratory measurements. Despite the large spread in the ice-nucleating particle (INP) concentrations in the parameterizations, the cloud properties and radiative fluxes had a tendency to form two groups, with the lower INP concentration category producing larger water path and low-level cloud fraction during winter and early spring, whereas the opposite occurred during the summer season. The stability of the lower troposphere was found to strongly correlate with low-cloud fraction and, along with the effect of ice nucleation, ice sedimentation, and melting rates, appears to explain the spring-to-summer reversal pattern in the relative magnitude of the cloud properties between the two categories of simulations. The strong modulation effect of the liquid phase on immersion freezing led to the successful simulation of the characteristic Arctic cloud structure, with a layer rich in supercooled water near cloud top and ice and snow at lower levels. Comparison with satellite retrievals and in situ data suggest that simulations with low INP concentrations more realistically represent Arctic clouds and radiation.

Current trends in the distribution of ice deposit fields on the territory of Ukraine during 1991-2020 regarding 1981-2010

The presented article is devoted to the study of modern trends in the spread of ice deposits on the territory of Ukraine in the last thirty years of 1991-2020 (new climate standard) relative to the period 1981-2010. recommended by WMO. The conducted research is related to the research work on the study of climate change carried out at the UkrSMI. Question status. Despite certain achievements in the study of the distribution of ice-frost deposits in the territory of Ukraine in the past, the task of determining the existing trends and subsequent changes in their distribution under the influence of climate change remains unresolved. The purpose of the study was to determine the current state and features of the distribution of the field of ice deposits on the territory of Ukraine with the identification of centers of increase and decrease in the average amount of such deposits, as well as trends relative to another observation period. Materials and methods. Data of actual instrumental observations of ice deposits at all meteorological stations of Ukraine for two periods 1991-2020 and 1981-2010 were used for processing. The main research methods were physical-statistical with the determination of the normalized values of the number of cases of such deposits and cartographic with the visualization of the results. The information obtained is not only informative, since it reflects the current trends in the distribution of one of the types of ice-frost deposits, which are adverse weather phenomena, but also allows you to plan the work of weather-dependent industries in more detail, ensuring their uninterrupted operation. Main results. It has been established that most of the deviations of the average number of ice cases for the study period relative to the period of 1981-2010. were insignificant, but in some areas during the cold season, especially in winter, they reached higher values. values. It has been established that in January and December there is a predominance of positive deviations of the average number of ice cases in Ukraine. Most of the centers of positive deviations are based on the territory of the western region from Volyn. Rivne and Zhytomyr regions to the Carpathians, as well as in the north of the Chernihiv and Sumy regions, as well as in a number of central regions from Vinnitsa to Poltava and Dnepropetrovsk regions. Also, noticeable foci of such deviations are observed in the north and east of the Kharkiv region, as well as in the north of the Luhansk region. They are noticeable in the south of the country. In February and March, foci of negative deviations were most often encountered. The most pronounced of them were observed in the western region in the territory from the Zhytomyr region to the Carpathian region, as well as in some central regions. In February, a focus of positive deposits was discovered in the north of the Chernihiv region. In April-October, the field of ice deposits for 1991-2020. compared to 1981-2010 practically did not change. In November, an increase in the number and spatial distribution of positive deviations of the average amount of ice deposits was revealed. They were mainly distributed in the central regions from Vinnitsa to the Poltava and Dnepropetrovsk regions, as well as in the east of the Kharkiv region and the north of the Luhansk region.

Troposphere-to-mesosphere microphysics of carbon dioxide ice clouds in a Mars Global Climate Model

We have implemented full CO2 ice cloud microphysics into the LMD Mars Global Climate Model (MGCM) and we have conducted the first global simulations. The microphysical model implementation follows the modal scheme used for water ice cloud microphysics in the MGCM, but includes specific aspects that need to be accounted for when dealing with CO2 ice clouds. These include nucleation of CO2 on water ice crystals and CO2 condensation theory adapted for the Martian conditions. The model results are compared to available observations globally, and separately for polar regions and equatorial mesosphere. The observed seasonal and latitudinal variability of the CO2 ice clouds is in general reproduced. The polar regions are covered by CO2 ice clouds during the winter as observed. Instead of forming only in the lowest 10–15 km of the atmosphere, they extend up to several tens of kilometers above the surface in the model, dictated by the modeled temperature structure. We have also quantified the contribution of the cloud microphysics to the surface CO2 ice deposits. Snowfall from these clouds contributes up to 10% of the atmosphere–surface ice flux in the polar regions in our simulations, in the range that has been indirectly deduced from observations. In the mesosphere, notable amounts of CO2 ice clouds form only when water ice crystals are used as condensation nuclei in addition to dust particles, and their spatial distribution is in agreement with observations. The mesospheric temperature structure, dominated by tides, dictates the longitudinal and seasonal distribution of these clouds. The seasonal and local time variations of the clouds are not fully reproduced by the model. There is a long pause in CO2 ice cloud formation in the model around the aphelion season, but clouds have been observed during this period, although with a lower apparition frequency. Modeled mesospheric clouds form mainly during the night and in the morning, whereas during the daytime, when most of the cloud observations have been made, the model rarely predicts clouds. These discrepancies could be explained by the strong dependence of the cloud formation process on mesospheric temperatures that are themselves challenging to reproduce and sensitive to the MGCM processes and parameters. The rare possibilities for nighttime observations might also bias the observational climatologies towards daytime detections. Future developments of the model consist in the inclusion of a possible exogenous condensation nucleus source in the mesosphere and the radiative effect of CO2 ice clouds.

Simulation investigation on the indirect effects due to sea-salt aerosols on the cloud ice during a tropical cyclone

This paper investigated the indirect effects due to sea-salt aerosols on tropical cyclones using the Weather Research and Forecasting model, coupled with a chemistry module (WRF-Chem). The parameterization of sea-salt aerosols in the model was operated. The domain-averaged vertically integrated cloud auto-conversion rates were 0.699 and 0.038 mm/h with and without the inclusion of the aerosol indirect effects, respectively. Cloud ice deposition and mixing ratio were higher with inclusion of indirect effects than without. Conversely, the cloud top temperature at a specified time was lower with indirect effects than without. When indirect effects of aerosols were included, the 0.01 g/kg contour line of the azimuthally and temporally averaged cloud ice mixing ratio increased by about 500 m. Overall, the inclusion of the aerosols indirect effects led to the extension of the cloud tops of tropical cyclones to greater heights.

RADIOCARBON CONSTRAINTS ON PERIODS OF POSITIVE CAVE ICE MASS BALANCE DURING THE LAST MILLENNIUM, JULIAN ALPS (NW SLOVENIA)

ABSTRACTCaves containing perennial ice deposits make up a little-known, but emerging part of the cryosphere under increasing scrutiny from the scientific community. M-17, a sag-type ice cave opening at 1879 m asl in the Tolminski Migovec massif of the Julian Alps (NW Slovenia) contains a perennial underground ice deposit whose paleoclimate sensitivity is poorly understood and whose longevity under current climate change is at risk. The past mass balance of this cave is constrained using wood macro-remains embedded in ice. Accelerator mass spectrometry radiocarbon dating of 18 wood samples embedded in ice provides the largest currently available dataset for a subterranean ice deposit in the southern European Alps. The reconstructed chronostratigraphy reveals three main phases of likely positive ice balance around 900–1100 AD, 1200–1300 AD, and 1700–1800 AD, as well as a period of negative mass balance around 1300–1400 AD. The onset of cave glaciation is deemed to have occurred no later than about 900 AD, with evidence of overall positive ice mass balance during multi-decadal periods characterized by cooler-than-average summers and wetter-than-average springs. Conversely, negative mass balance is recorded during a period warmer-than-average summers and dry springs. The cave has experienced ice mass loss since its discovery in the 1980s.

Orbital Forcing of Martian Climate Revealed in a South Polar Outlier Ice Deposit.

Deciphering paleoclimate on Mars has been a driving goal of Martian science for decades. Most research has addressed this issue by studying Mars' large polar layered deposits (PLDs) as a paleoclimate proxy, but the certainty to which we know the link between climate and orbit is debated. Here, we instead consider the record of other, smaller ice deposits located within craters separated from the PLDs using images from NASA's High Resolution Imaging Science Experiment camera and signal processing techniques. We show that the climate record in Burroughs Crater (72.3°S, 116.6°E) contains robust evidence of orbital forcing, with periodicities that have wavelengths of 15.6 and 6.5 m. The ratio of these dominant wavelengths is 2.4, the same as the ratio between the periods of Mars' obliquity changes and orbital precession. This result suggests orbital control of recent Mars climate, and would imply an average ice accumulation rate of 0.13 mm/yr over 4.5 Myr in this region.

Arecibo S-band Radar Characterization of Local-scale Heterogeneities within Mercury’s North Polar Deposits

Abstract Ground-based planetary radar observations first revealed deposits of potentially nearly pure water ice in some permanently shadowed regions (PSRs) on Mercury’s poles. Later, the MESSENGER spacecraft confirmed the icy nature of the deposits, as well as their location within PSRs. Considering the geologic context provided by MESSENGER, we further characterized the north polar deposits by pairing spacecraft data with new Arecibo S-band radar observations. Here we show that some ice deposits within PSRs have a gradational pattern in their radar properties that is likely associated with differences in ice purity. Radar-bright features with a circular polarization ratio μ c > 1 can be characterized by water ice with ≳3% impurities by volume while those with μ c < 1 by ≳20% impurities. Furthermore, areas in PSRs with μ c < 1 typically surround locations of stronger radar backscatter with μ c > 1. Therefore, deposits of nearly pure water ice are likely surrounded by lower-purity material, such as water-ice-rich regolith, which could be the result of impact gardening or the crater’s thermal environment. However, such deposits are not always colocated within large polar craters where ice should be the most stable, even at the surface. In fact, we found that there is no significant difference between the radar backscattering properties of deposits thought to have surficial ice and those with buried ice. Our results also help improve the identification of icy reservoirs elsewhere, such as the Moon. Indeed, we found that μ c is not an adequate diagnostic, but rather the radar backscatter in each circular polarization independently provides information to identify water-ice deposits.

New method for the calibration of a road condition sensor

PurposeThis study aims to improve the calibration accquracy of the road condition sensor. A road condition sensor is widely used to detect water or ice deposits on the road to assess associated driving risks. Its quantitative calibration is central to the thickness measurement accuracy and conventionally performed using the single fitting method-based calibration method. One existing limitation is that the distribution characteristics of calibration data of different road conditions are diversified, which leads to the fitting error can not be minimized when using the conventional calibration method. Thus, the multiple fitting methods-based calibration method is developed to realize an optimal calibration for the road condition sensor.Design/methodology/approachA fitting method assignment for the calibration data of different road conditions was introduced to realize an optimal combination for fitting method and calibration data. In the experiments, the calibration methods were tested in the absence of measurement errors, then tested with calibration data, and finally, in the covering thickness measurement.FindingsThe comparison results indicate that compared with the conventional calibration method, the multiple fitting methods-based calibration method cuts the fitting error in the quantitative calibration by 13.3% and contributes to reducing the thickness measurement error by 8.11% for different road conditions.Originality/valueThe multiple fitting methods-based calibration method has been successfully applied for quantitative calibration and shown to reduce calibration errors. The comparison between different calibration methods demonstrates the superior performance of the new calibration method.

The Basal Detectability of an Ice‐Covered Mars by MARSIS

AbstractThe detection of anomalously strong relative basal reflectivity beneath the Martian South Polar Layered Deposits (SPLD) from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) has led to hypotheses suggesting the presence of basal materials such as liquid water. Here, we propose a forward approach to assess whether such a high signal could be produced by a Martian terrain currently exposed at the surface without liquid water. We convert existing MARSIS surface reflectivity measurements into a basal reflectivity as if it were overlaid by an SPLD‐like ice deposit. 0.3%–2% of the surface could produce basal reflections of magnitude similar to the SPLD measurements in the assumption of a 10% impure ice. An ice loss tangent 0.01 is required to prevent any of the current Martian surface from producing a bright SPLD‐like basal reflection. The detected bright terrains are gathered within volcanic constructs of diverse geologic epoch.

A Review of Ice Core Drilling in Cave Environment – Challenges, Achievements and Future Directions

Worldwide, more than 141 m of ice cores has been extracted from 20 cave ice deposits, with the drilling projects focusing mainly in Central European caves. The fact that half of the cave ice cores (3 out of 6) published in 2020 represent non-European localities, however, predicts that an increasing number of cave ice drilling projects will be carried out in the near future in other geographical areas hosting ice caves. Based on the gathered experience the most commonly encountered technical challenge of ice-core drilling problems in cave environment is englacial rocky/woody debris. The complex stratigraphy of cave ice deposits represents a crucial methodological problem. We propose an (Cave Ice Sedimentary Architecture and Deposition - CISAD) approach to take into consideration of the stratigraphic peculiarities of the investigated cave ice deposit and additional crucial meta-data before establishing the location of a drilling site best-suited to obtain the highest quality paleoenvironmental data.

Challenges of operating a drilling instrument on a small rover at the lunar poles - LVS-PIE phase A study results

The “LVS-PIE Phase A″ project successfully investigated the feasibility of using the Lunar Volatiles Scout instrument on the ispace Polar Ice Explorer rover to search for possible cold-trapped water ice deposits at the lunar poles. The suitability of the two systems for a joint mission was studied based on identified conflicts between both initial systems, such as the envelope for integration or the power budget. The interfaces were made compatible, mechanical structure and mechanisms were updated to enable system integration and thermal simulations were performed to refine the thermal design for safe operation within the thermal limits under lunar conditions. Thermal extraction simulations for the instrument constrained the power requirement during the instrument's heating phase. Real drilling down forces and reaction torques were determined with representative experiments for both rover and instrument revealing stable conditions during the envisioned drilling process. In the developed mission scenario, operational feasibility of the LVS-PIE mission concept was demonstrated using a notional traverse, remote sensing data and investigation of technical budgets. The mission can reach sites of high scientific interest at the lunar poles and perform relevant measurements with the instrument. A joined mission consisting of an instrument package for drilling and gas analysis on a rover below 20 ​kg total mass is found to be technically feasible and scientifically valuable.

SHARAD Observations of Temporal Variations of CO2 Ice Deposits at the South Pole of Mars

Mars’s polar regions are covered by kilometers-thick layered deposits which carry a record of the planet’s climate history. The deposition and volatilization of the shallow CO2 deposits in the south pole have a large impact on the planet’s atmosphere and environment. This research focuses on the timing variation of the thickness of the shallow deposits based on the SHARAD data collected from the past 11 terrestrial years, and analysis of the contributing factors based on the volatilization and deposition mechanisms of surface and subsurface materials. In this work, we selected more than four thousand data points, covering several seasons and Martian years, to extract radar echoes and calculate the thickness changes in the subsurface layer over time. We found that the thickness of the CO2 layer becomes thinner in the summer, with seasonal variation in the range of ~16–45 m. The thickness variations have a Gaussian-like distribution and do not increase with the distance between the compared node pair, implying that the phenomenon is not caused by regional differences. The overall thickness within the 11 terrestrial years does not show a clear trend of thickening or thinning, indicating a moderate vertical change of the southern deposits.

Long-term mass-balance monitoring and evolution of ice in caves through structure from motion–multi-view stereo and ground-penetrating radar techniques

This study investigates the application of a terrestrial structure from motionmulti-view stereo (SfM-MVS) approach combined with ground-penetrating radar (GPR) surveys for monitoring the surface topographic change of two permanent ice deposits in caves located in the Julian Alps (south-eastern European Alps). This method allows accurate calculation of both seasonal and annual mass balance, estimating the amount of ice inside caves. The ground-based SfM approach represents a low-cost workflow with very limited logistical problems of transportation and human resources and a fast acquisition time, all key factors in such extreme environments. Under optimal conditions, SfM-MVS allows sub-centimetric resolution results, comparable to more expensive and logistically demanding surveys such as terrestrial laser scanning (TLS). Fourteen SfM acquisitions were made between the 2017–2020 ablation seasons (i.e. July–October) while 2 GPR surveys were acquired in 2012. The obtained dense point clouds and digital terrain models (DTMs) made possible a reliable calculation of topographic changes and mass balance rates during the analysed period. The integration of SfM-MVS products with GPR surveys provided comprehensive imaging of the ice thickness and the total ice volume present in each of the caves, proving to be a reliable, low cost and multipurpose methodology ideal for long-term monitoring.

Resource potential of lunar permanently shadowed regions

The lunar polar regions contain permanently shadowed regions (PSRs) or local topographic depressions that never receive direct sunlight. These environments (<110 K) have the potential to cold-trap volatile materials in the form of ice, which are essential resources for exploration and industrialization of cislunar space and the Solar System. Orbital observations and those from the LCROSS impactor experiment provide evidence of the existence of water ice and other cold-trapped volatiles in PSRs; however, constraints on volatile abundance and distribution remain ambiguous as individual observations are not always in concord. Here we compile observations indicating the presence of volatiles from ten remotely sensed datasets in 65 PSRs to estimate the locations and mass of water ice deposits. Faustini, Cabeus, de Gerlache, Shoemaker, Haworth, Sverdrup, Slater, and Amundsen are likely the most resource-rich PSRs. Based on co-locations of observations indicative of surface frost and subsurface hydrogen abundance, we find that the craters with the highest potential mass in metric tons (t) of water ice include Cabeus (~11 × 106 t), Shoemaker (~5 × 106 t), Faustini (~4 × 106 t), de Gerlache (~3 × 106 t), and Haworth (~3 × 106 t). Future prospecting of lunar volatiles and water ice is contingent on filling knowledge gaps in resource potential, notably accurate measurements of grade and depth of volatiles. Our proposed ranking and estimates for resource tonnage are a tool to guide future orbital and landed missions that could accurately determine the resource potential of PSR deposits.

Multi-Year Evolution of 75 Snow and Ice Deposits in Schachtdolines and Shafts of Recently Deglaciated Karst Terrain: Observations from Mount Canin-Kanin, Julian Alps, Europe

Multi-Year Evolution of 75 Snow and Ice Deposits in Schachtdolines and Shafts of Recently Deglaciated Karst Terrain: Observations from Mount Canin-Kanin, Julian Alps, Europe

Multi-Year Evolution of 75 Snow and Ice Deposits in Schachtdolines and Shafts of Recently Deglaciated Karst Terrain: Observations from Mount Canin-Kanin, Julian Alps, Europe

Multi-Year Evolution of 75 Snow and Ice Deposits in Schachtdolines and Shafts of Recently Deglaciated Karst Terrain: Observations from Mount Canin-Kanin, Julian Alps, Europe

ВІДКЛАДЕННЯ ОЖЕЛЕДІ КАТЕГОРІЇ НЯ (НЕБЕЗПЕЧНА) ТА СГЯ (СТИХІЙНА) МАСОВОГО ХАРАКТЕРУ РОЗПОВСЮДЖЕННЯ НА ТЕРИТОРІЇ УКРАЇНИ ПРОТЯГОМ ДЕСЯТИРІЧ 1991-2000 рр., 2001-2010 рр., 2011-2020 рр.

The presented work is devoted to the study of ice deposits of the category of DP (dangerous) and SHP (spontaneous) of mass distribution in Ukraine during the last 30 years (1991-2020) at certain ten-year intervals. It is established that the period 1991-2000 will be distinguished by the total number of cases of mass distribution of ice deposits of the DP category, and the periods 2001-2010 and 2011-2020 are almost equivalent. The peculiarities of the manifestation of cases of mass deposition of ice of the DP category on the territory of Ukraine in separate months of the studied ten – year intervals are shown and the years in which such cases were the most are revealed. Thus, the largest number of such cases was observed in 1998, 1999, 2009, 2013, 2014, 2018. That is, in the last decade the number of years with such cases has increased slightly. It was found that in the studied decades the largest number of such cases was detected in the winter months (December-February), but from decade to decade they had their own dynamics, namely – their predominant increase in January (relative to 1991-2000) and volatile change in February and December (from period to period there is a variation in the number of cases). Thus, in February 2001-2010, compared to 1991-2000, there is an increase in the number of such cases, and in 2011-2020, on the contrary, there is a rather sharp decrease. In December 2001-2010, the number of such cases decreased slightly compared to 1991-2000, and in 2011-2020 slightly increased. In March, the number of cases of mass spread of ice deposits of the DP category did not change during the studied ten-year periods. In November, the largest number of such cases was observed during 1991-2000. The largest contribution to the number of such cases was in 1998 and 1999. During 2001-2010, it decreased significantly, and in the following decade 2011-2020 it more than doubled compared to with the last decade. Cases of mass deposition of ice in the SHP category have also changed over the decades under study. The largest number of them was observed during 1991-2000 and 2011-2020, and in the first decade they were mostly observed in November, and in the last in January. For the most part, ice deposits of the NE and OHS categories during their mass distribution are observed at 2 or 3-4 stations and within 2 (3-4) oblasts. However, in some cases, especially in the winter months, they may be larger.