Occurrence Of Ice Research Articles

Information on operational sea ice products and current and future activities of the German ice service

The ice service at the German Federal Maritime and Hydrographic Agency and its predecessors has been committed to the safety and easiness of ship navigation for more than 100 years. Within this paper, an overview of the operational products issued by the German ice service on a daily to weekly basis throughout the northern hemisphere winter season is given. These comprise written reports, ice charts, NAVTEX messages, and messages via the Global Telecommunication System to inform about the sea ice situation in German coastal waters, the Baltic Sea, and worldwide. Furthermore, the ice service has systematically collected ice observation data along the German North Sea and Baltic Sea coast since the winter of 1896/1897. The history of the German ice service is presented to put the sea ice data into context of the observation technologies used in the course of the existence of the ice service. These long-term observations enable climatological analyses of the sea ice cover in German coastal waters necessary for the safe operation of offshore infrastructure. An evaluation of the data shows a recent decline in sea ice occurrence in the Baltic Sea and German Bight. Current work is ongoing to preserve more of the historic data in digital form and also to transform the products to conform to modern standards in digital technologies and interactive solutions for the customers.

Sea Ice Interannual Variability and Sensitivity to Fall Oceanic Conditions and Winter Air Temperature in the Gulf of St. Lawrence, Canada

AbstractThe Gulf of St. Lawrence has been nearly free of sea ice in the winter six times in its recorded history, four of which have occurred since 2010. This study examines the inter‐annual variability of sea ice cover characteristics (1969–2024) and winter mixed layer heat content (1996–2024), their sensitivity to fall oceanic conditions (since fall of 1995) and to winter air temperatures. The study finds no relationship between fall oceanic conditions with either the first occurrence of sea ice, maximum seasonal estimated volume or winter mixed layer heat content. However, it shows that the first occurrence of sea ice in the northwestern Gulf is related to the timing of sea surface temperature crossing the 1°C threshold with a lag time of 30–37 days, and with air temperature dropping below −2°C with a lag of 37–44 days; longer lags have weak correlations. The seasonal maximum conditions in area or estimated volume can be estimated by the preceding measurements of the same metrics with a lead time of only 29 days for volume and 36 days for area. The average air temperature over the Gulf between December and February or March is highly correlated to seasonal maximum sea ice area and estimated volume, as well as ice season duration. The six nearly ice‐free winters correspond to the warmest December to February (or December to March) average air temperatures over the Gulf. A warming of >1.9°C–2.4°C (DJFM) or >2.2°C–2.9°C (DJF) above the 1991–2020 climatology leads to nearly ice‐free conditions.

Monitoring of the Icing Process and Simulation of Its Formation Mechanism in the Cut Slope of Beihei Highway

Icing in cut slopes is a serious risk to transportation safety in cold regions. Research on the occurrence process and mechanism of icing is a prerequisite for proposing effective management measures. We took the cut slopes of the K162 section of the Beihei Highway as the research object. We used a combination of field investigation, geological exploration, monitoring, and simulation to study and analyze the power source, occurrence process, and triggering mechanism of icing in cut slopes. The results show that the geologic type of this cut slope is a mudstone–sandstone interaction stratum. Abundant shallow groundwater is the source of water for icing. The excavation of cut slopes extends the effect of negative temperatures on groundwater flow during the winter period. The process of ice formation in cut slopes can be described as follows: As the environmental temperature drops, the surface soil begins to freeze, resulting in a gradual narrowing of the water channel; then, the groundwater flow is blocked, so that the internal pressure begins to rise. When the internal pressure of the pressurized groundwater exceeds the strength of the frozen soil, groundwater overflows from the sandstone layer to the surface, forming icing. The high pore water pressure inside the cut slope is the precursor for the occurrence of icing. The dynamic pressure of the pore water pressure is the main driving force for the formation of icing in cut slopes. The obstruction of the water channel due to ground freezing is the triggering condition for ice formation in cut slopes.

Predicting black ice-related accidents with probabilistic modeling using GIS-based Monte Carlo simulation.

Black ice, a phenomenon that occurs abruptly owing to freezing rain, is difficult for drivers to identify because it mirrors the color of the road. Effectively managing the occurrence of unforeseen accidents caused by black ice requires predicting their probability using spatial, weather, and traffic factors and formulating appropriate countermeasures. Among these factors, weather and traffic exhibit the highest levels of uncertainty. To address these uncertainties, a study was conducted using a Monte Carlo simulation based on random values to predict the probability of black ice accidents at individual road points and analyze their trigger factors. We numerically modeled black ice accidents and visualized the simulation results in a geographical information system (GIS) by employing a sensitivity analysis, another feature of Monte Carlo simulations, to analyze the factors that trigger black ice accidents. The Monte Carlo simulation allowed us to map black ice accident occurrences at each road point on the GIS. The average black ice accident probability was found to be 0.0058, with a standard deviation of 0.001. Sensitivity analysis using Monte Carlo simulations identified wind speed, air temperature, and angle as significant triggers of black ice accidents, with sensitivities of 0.354, 0.270, and 0.203, respectively. We predicted the probability of black ice accidents per road section and analyzed the primary triggers of black ice accidents. The scientific contribution of this study lies in the development of a method beyond simple road temperature predictions for evaluating the risk of black ice occurrences and subsequent accidents. By employing Monte Carlo simulations, the probability of black ice accidents can be predicted more accurately through decoupling meteorological and traffic factors over time. The results can serve as a reference for government agencies, including road traffic authorities, to identify accident-prone spots and devise strategies focused on the primary triggers of black ice accidents.

Sea Ice‐Driven Iceberg Drift in Baffin Bay

AbstractBaffin Bay is the travel destination of most icebergs calving from west Greenland. They commonly follow the bay's cyclonic circulation and might end up far south along the coast of Newfoundland and Labrador, where many shipping routes converge. Given the hazard that icebergs pose to marine transportation, understanding their distribution is fundamental. One of the forces driving iceberg drift arises from the presence of sea ice. Observations in the Southern Ocean indicate that icebergs get locked in thick and concentrated sea ice. We present observations that support the occurrence of this sea ice locking mechanism (SIL) in Baffin Bay as well. Most iceberg models, however, represent the sea ice force over an iceberg as a simple drag force. Here, we implement a new parameterization in the iceberg module of the Nucleus for European Modeling of the Ocean (NEMO‐ICB) to represent SIL. We show that, by using this new parameterization, icebergs are more likely to travel outside of the Baffin Island Current during winter, which is supported by satellite observations. There is a slight improvement in the representation of iceberg severity along the coast of Newfoundland and Labrador and a slight shift of iceberg melt toward this region and Lancaster Sound/Hudson Strait. Although the impacts of icebergs on sea ice are still not represented, and targeted observations are needed for model calibration regarding sea ice concentration thresholds from which icebergs get locked, we are confident that this model improvement takes iceberg modeling one step forward toward reality.

Methane pumping by rapidly refreezing lead ice in the ice-covered Arctic Ocean

If and how the sea ice cycle drives the methane cycle in the high Arctic is an open question and crucial to improving source/sink balances. This study presents new insights into the effects of strong and fast freezing on the physical–chemical properties of ice and offers implications for methane fluxes into and out of newly formed lead ice. During the 2019–2020 transpolar drift of the Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC), we took weekly samples of growing lead ice and underlying seawater at the same site between January and March 2020. We analyzed concentrations and stable carbon isotopic signatures (δ13C–CH4) of methane and calculated methane solubility capacities (MSC) and saturation levels in both environments. During the first month, intense cooling resulted in the growth of two-thirds of the final ice thickness. In the second month, ice growth speed decreased by 50%. Both growth phases, disentangled, exposed different freeze impacts on methane pathways. The fast freeze caused strong brine entrapment, keeping the newly formed lead ice permeable for 2 weeks. These physical conditions activated a methane pump. An increased MSC induced methane uptake at the air–ice interface, and the still-open brine channels provided top-down transport to the ocean interface with brine drainage. When the subsurface layer became impermeable, the top-down pumping stopped, but the ongoing uptake induced a methane excess on top. During the second growth phase, methane exchange exclusively continued at the ice–ocean interface. The shift in the relative abundance of the 12C and 13C isotopes between lead ice and seawater toward a 13C-enrichment in seawater reveals brine drainage as the main pathway releasing methane from aging lead ice. We conclude that in winter, refrozen leads temporarily function as active sinks for atmospheric methane and postulate that the relevance of this process may even increase when the Arctic fully transitions into a seasonally ice-covered ocean when leads may be more abundant. To highlight the relevance of methane in-gassing at the air–ice interface as a potential but still unconsidered pathway, we include estimates of the occurrence and frequency of young lead ice from satellite observations of leads during MOSAiC.

Modeling the Link Between Air Convection and the Occurrence of Short‐Term Permafrost in a Low‐Altitude Cold Talus Slope

ABSTRACTWe extend a numerical modeling approach developed to explicitly model convective heat transfer in periglacial landforms to represent the ground thermal regime of low‐altitude talus slopes. Our model solves for heat conduction and accounts explicitly for air convection adopting a Darcy term with a Boussinesq approximation for air circulation in the porous ground. Numerical model experiments for the low‐altitude talus slope Dreveneuse, Switzerland, confirm that air convection is the key to forming and maintaining ground ice. In the model, the porous talus slope is underlain by a layer of water‐bearing morainic material. In years, where the gradient between air and talus temperature is sufficiently large to result in increased convection and therefore cooling, ground ice forms due to air convection within the porous material and lasts for more than a year. It is only by considering convection that the model is able to represent the occurrences of ground ice, in accordance with temperature observations on‐site. These findings are important, as they confirm that ground ice can be formed and maintained in landforms with a mean annual air temperature > 0°C if ground air convection is present combined with the presence of water.

Research on the Identification of Typical Terrain Patterns in Yunnan Province Based on the K-Means Technology

Wire icing is a prevalent challenge in both industrial and scientific domains, and it is widely acknowledged that terrain and water vapor are significant contributing factors in the formation of wire icing. Consequently, the identification of terrains that are prone to inducing water vapor uplift serves as the scientific foundation for predicting ice accumulation on power lines. Yunnan Province, a mountainous province in China, features a large elevation difference. In winter, this region is prone to wire, pole and tower icing, which can affect power transmission and cause economic and property losses. Therefore, it is necessary to conduct research on the identification of typical terrain patterns in this region. In previous terrain studies, more attention has been focused on slope and aspect, watershed analysis and terrain profile analysis. When the purpose of the terrain identification is to analyze which terrains are more prone to collecting water vapor, we hope to obtain slightly larger terrain blocks and analyze the water vapor sources for different terrains in order to identify typical terrains that are conducive to icing formation. A new technology for identifying terrain patterns based on the K-means clustering method is proposed in this study to explore the typical terrain in Yunnan province. Additionally, the influences of different terrain patterns on water vapor movement are also analyzed. The results indicate that the typical terrains in Yunnan are “Valley-Air Channel”, “Topographic Uplifting”, “Ravine”, “Mountain Pass” and “Alpine Divide” patterns. The results show that the identified typical terrain is consistent with observations from satellite images, which verifies the effectiveness of this identification method. Among these five typical terrains, the “Valley-Air Channel”, the “Topographic Uplifting” and the “Mountain Pass” terrains are prone to collecting water vapor and forming ice cover. The “Alpine Divide” terrain is also prone to accumulating water vapor on both sides to form ice cover. The identified typical terrain demonstrates that typical terrain patterns near water bodies are more prone to the occurrence of wire, pole and tower icing because these areas are abundant in water vapor, and the extensive water vapor is easily condensed under the effects of terrain uplifting and cooling. In these key areas, existing wires and towers, as well as those to be constructed in the future, deserve our special attention.

Ground Penetrating Radar Survey of Arctic Polygonal Wedge Structures

Ground Penetrating Radar Survey of Arctic Polygonal Wedge Structures

Gas chromatography-mass spectrometry selected ion monitoring and gas chromatography-tandem mass spectrometry selected reaction monitoring analyses of mono-, di- and tri-unsaturated C25 highly branched isoprenoid alkene biomarkers in sea ice and sediment samples: A comparative study.

The efficiency of selected ion monitoring (SIM) and selected reaction monitoring (SRM) analyses for the quantification of three mono-, di- and tri-unsaturated highly branched isoprenoid (HBI) alkenes (IP25 , IPSO25 and HBI III, respectively), often used as proxies for the occurrence of Arctic and Antarctic sea ice or the adjacent open waters, was compared. Gas chromatography (GC)-mass spectrometry (MS)/SIM and GC/MS/MS/SRM analyses were carried out on dilute solutions made from purified standards of these three HBIs, and then on hydrocarbon fractions of several sediment and sea ice sample extracts. More efficient and specific SRM transitions were selected after collision-induced dissociation of each precursor ion at different collision energies. SRM analysis avoided any overestimation of IP25 resulting from the contribution of the coeluting 13 C mass isotopomer of IPSO25 (M+ ˙ + 2) to the SIM target ion. In contrast, SRM analysis is less reliable for IPSO25 quantification in cases where several regio-isomers are present, likely due to intense double bond migrations following electron impact. In the case of HBI III, SRM analysis constitutes a potentially suitable alternative to SIM analysis, especially in terms of improving limit of detection. Despite the intense migrations of HBI double bonds under electron ionization, the selected SRM transitions should be more suitable than SIM target ions for IP25 and HBI III quantification in complex hydrocarbon fractions of natural samples. However, the advantage is less evident for IPSO25 due to the presence of numerous regio-isomers.

Characterizing Ice Nucleating Particles Over the Southern Ocean Using Simultaneous Aircraft and Ship Observations

AbstractSupercooled liquid clouds are ubiquitous over the Southern Ocean (SO), even to temperatures below −20°C, and comprise a large fraction of the marine boundary layer (MBL) clouds. Earth system models and reanalysis products have struggled to reproduce the observed cloud phase distribution and occurrence of cloud ice in the region. Recent simulations found the microphysical representation of ice nucleation and growth has a large impact on these properties, however, measurements of SO ice nucleating particles (INPs) to validate simulations are sparse. This study presents measurements of INPs from simultaneous aircraft and ship campaigns conducted over the SO in austral summer 2018, which include the first in situ observations in and above cloud in the region. Our results confirm recent observations that INP concentrations are uniformly lower than measurements made in the late 1960s. While INP concentrations below and above cloud are similar, higher ice nucleation efficiency above cloud supports model simulations that the dominant INP composition varies with height. Model parameterizations based solely on aerosol properties capture the mean relationship between INP concentration and temperature but not the observed variability, which is likely related to the only modest correlations observed between INPs and environmental or aerosol metrics. Including wind speed in addition to activation temperature in a marine INP parameterization reduces bias but does not explain the large range of observed INP concentrations. Direct and indirect inference of marine INP size suggests MBL INPs, at least during Austral summer, are dominated by particles with diameters smaller than 500 nm.

Graphene-enhanced, wear-resistant, and thermal-conductive, anti-/de-icing gelcoat composite coating

Wind power is considered as a sustainable and environmentally friendly energy source. However, the occurrence of icing poses significant challenges to energy production, particularly in frigid regions during the winter season. Conventional strategies employed for preventing and removing ice formation have proven inadequate due to their inability to satisfy intricate requirements or their high energy consumption. In this study, a commercial gelcoat coating was adopted as an anti-/de-icing coating by introducing different concentrations of graphene and boron nitride into the gelcoat coating through physical mixing. Extensive investigations were conducted on the correlation between anti-/de-icing, wear resistance, and thermal conductivity. Notably, the incorporation of nanoparticles induced a rise in the surface roughness, resulting in prolonged resistance to water icing on the coated surface. The wear resistance and thermal conductivity of the composite coating were enhanced through the inclusion of boron nitride and graphene. The building of thermal conductive particle networks improved thermal conductivity which can lead to improved heat transfer and heat distribution. At the same time, the enhanced gelcoat composite coating exhibited exceptional passive anti-/de-icing performance and wear resistance. This coating can replace commercial coatings to improve anti-/de-icing efficiency for the existing active heating anti-/de-icing techniques available in the market.Graphical The graphene was employed to enhance the thermal conductivity, wear resistance, and anti-/de-icing properties of the turbine coating.

Modeling and analysis of ice condensation on bridge deck pavement surface based on heat transfer theory and finite element method

Bridge surfaces usually freeze more easily than road surfaces in wet and cold conditions, which is unfavorable to traffic safety. This study aims to develop an ice prediction model for bridge deck pavement structures by integrating external climatic factors and internal structure parameters, and to analyze the mechanism of ice condensation. This model adopted finite element analysis to deal with the heat transfer problem and the latent heat during the phase change process. A series of experiments were designed to validate the model, and the relative difference was around 10 %. Results shown that: among external climatic factors, the impact of changes in water accumulation on ice formation is not significant. Meanwhile, the air temperature has the greatest impact, and there is a non-linear relationship between wind speed and the initial freezing time. In the study on the effect of aging, it was found that aged asphalt concrete pavement would freeze earlier and melt later compared to new. When comparing different structures, it was observed that the initial freezing time of the bridge deck pavement structure was 0.8 h earlier than the road structure, and the total freezing time was 2.8 h shorter than the road structure. It was also found that the lower thermal conductivity would delay the occurrence of icing when the bridge deck pavement structure was in a cooling stage. Finally, it was observed that the vehicle speed played a critical role in determining the direction of the heat flow with a specific value, and the value would increase as the temperature difference decreased. This prediction model is useful for transportation agencies to understand the mechanism of pavement ice formation and ensure traffic safety in winter.

Spatiotemporal distribution characteristics of sea ice disasters in the Northern China Sea from 2001 to 2020

The sea ice disaster is one of the major marine disasters in China. The presence of sea ice poses a potential threat to the social-environmental system in the Northern China Sea during winter. The study focused on investigating the spatiotemporal distribution characteristics of sea ice disasters in the Northern China Sea during 2001–2020, including exploring the variation of sea ice hazards, climate drivers influencing sea ice occurrence, and the subsequent impacts on maritime activity and marine aquaculture. The results show that the sea ice grade in the Bohai and Northern Yellow Seas (BNYS) exhibited a slight downward trend (−0.40/decade, P > 0.10) during the past two decades. The winter temperature and the frequency of cold waves are the primary local climate factors for sea ice variation. The decrease in sea ice grade in the BNYS due to global climate change does not eliminate the occurrence of extreme events. However, the potential for more severe damages remains. It is worth noting that the winters of 2010, 2011, and 2013 stand out as periods with the highest recorded direct economic losses caused by sea ice hazards. In terms of spatial distribution, Liaoning and Shandong provinces have experienced the most severe impacts of sea ice hazards. Sea ice has a negative impact on the throughput of ports that are influenced by sea ice. Significant moderate negative correlations (r = −0.40, P < 0.10) have been observed between port throughput and the sea ice index in Yingkou, Jinzhou, and Tianjin ports. Moreover, the mariculture industry emerged as the primary sector affected by sea ice disasters in the Northern China Sea between 2001 and 2020. Attention should be paid to Haizhou Bay shortly as marine aquaculture in this area has been seriously affected by sea ice in the past five years. In the future, it is crucial to prioritize more accurate and refined monitoring and forecasting of sea ice, enhance the provision of effective icebreaking and pilot services, and optimize the fishery industry structure to prevent sea ice disasters in the Northern China Sea.

The habitability conditions of possible Mars landing sites for life exploration

A major focus of Mars exploration is the search for life. Since the Viking landers in the 1970's, no mission has searched for evidence of modern life. Future landed missions with this objective will require a landing site that optimizes the potential for current or geologically-recent habitable conditions. While the definition of habitability is broad, we concentrate on two conditions for habitability of temperature and water activity. In addition, we consider the access to subsurface ice (e.g., via a lander drill) as a major requirement. To examine potential landing sites, we utilize a standard model of temperature and ground-ice stability to explore a range of latitudes for the past 2.5 Myrs of orbitally induced climate change. We find that in the current epoch, habitable conditions do not occur within the ice-rich permafrost, where stable ice is limited to poleward of ∼47°N. Habitable conditions defined as favorable to metabolic activity in Earth-like potential Mars organisms did occur seasonally during periods of high obliquity >33°, when ground ice would have been more ubiquitous. The most recent occurrence was about 510 kyrs ago when temperatures and water activities seasonally exceeded the threshold for metabolic activity of −40 °C and 0.6, respectively. Periods such as these last 10s of kyrs at each occurrence. At no time or location do habitability conditions favor propagation (cell replication above −18 °C) in Earth-like Mars organisms. We present a model of subsurface stratigraphy based on the occurrence of ground ice, the age of the ice, and history of habitable conditions. From this stratigraphy we find that all latitudes offer some potential for life exploration. However, middle-latitude sites (47°N to 61°N) offer access to 100-kyr-old ice that experienced past habitable conditions, while high-latitudes sites (>61°N) offer this plus access to “ancient ice” > > 1 Myrs old. Access to, and comparison between, multiple stratigraphic layers with differing ages and histories will maximize the science results of a life exploration mission. These latitude limits may vary slightly with surface conditions of slope and soil properties.

Characterization of icing conditions using aircraft reports and satellite data

A sample of 115 aircraft icing events in the Western Europe and Northeastern Atlantic sector, identified in aircraft pilot reports (PIREPs), is assessed in terms of spatio-temporal distribution and cloud characteristics, using satellite observations and products. Within our database, most of the reported events occur between October and February, although a few cases were identified during late spring and even summer months. Icing conditions are generally reported at mid-troposphere, with 82.7% and 78.6% of moderate and severe icing, respectively, identified between FL100 and FL250 (≈ 3–7.6 km). Satellite observations allow the identification of icing-prone conditions and also provide an independent means of validating some of the data in the aircraft reports. It is shown that icing occurs mainly within opaque clouds, with ice cloud-tops, or mixed phase (ice and water), noting the severe events, take place mostly under mixed-phase cloud-tops. Accordingly, most events were associated with middle and high opaque clouds, with 10.8μm brightness temperatures (BT10.8) between −40 and − 8 °C. Moreover, a detailed analysis of three events, making use of model, satellite and synoptic observations, illustrates the occurrence of aircraft icing in precipitating clouds. Within those cases, one occurred below the upper layer of a thick nimbostratus associated with an occluded low centred in the Bay of Biscay. The second event, reported as severe, as in the former case, took place within low clouds over southern England in association with northwesterly winds driven by a complex low. Finally, a moderate event happened over southern Portugal in association with a cold front, near the cloud top of nimbostratus. In all cases, the icing index operational at the Portuguese Weather Service, based on the European Centre for Medium-range Weather Forecasts (ECMWF) model, was able to predict prone-icing conditions, with higher severity in the severe cases.

Monitoring Arctic thin ice: a comparison between CryoSat-2 SAR altimetry data and MODIS thermal-infrared imagery

Abstract. Areas of thin sea ice in the polar regions not only are experiencing the highest rate of sea-ice production but also are, therefore, important hot spots for ocean ventilation as well as heat and moisture exchange between the ocean and the atmosphere. Through co-location of (1) an unsupervised waveform classification (UWC) approach applied to CryoSat-2 radar waveforms with (2) Moderate Resolution Imaging Spectroradiometer-derived (MODIS) thin-ice-thickness estimates and (3) Sentinel-1A/B synthetic-aperture radar (SAR) reference data, thin-ice-based waveform shapes are identified, referenced, and discussed with regard to a manifold of waveform shape parameters. Here, strong linear dependencies are found between binned thin-ice thickness up to 25 cm from MODIS and the CryoSat-2 waveform shape parameters that show the possibility of either developing simple correction terms for altimeter ranges over thin ice or directing adjustments to current retracker algorithms specifically for very thin sea ice. This highlights the potential of CryoSat-2-based SAR altimetry to reliably discriminate between occurrences of thick sea ice, open-water leads, and thin ice within recently refrozen leads or areas of thin sea ice. Furthermore, a comparison to the ESA Climate Change Initiative's (CCI) CryoSat-2 surface type classification with classes sea ice, lead, and unknown reveals that the newly found thin-ice-related waveforms are divided up almost equally between unknown (46.3 %) and lead type (53.4 %) classifications. Overall, the UWC results in far fewer unknown classifications (1.4 % to 38.7 %). Thus, UWC provides more usable information for sea-ice freeboard and thickness retrieval and at the same time reduces range biases from thin-ice waveforms processed as regular sea ice in the CCI classification.

Разработка программного модуля построения карт распределения вероятностей встречи с морским льдом для изучения дальневосточных морей

The article presents a description of the developed software module for creating maps of the probability distribution of encountering sea ice. The module allows to process collections of raster map files based on satellite data and obtain vector maps of the probability distribution of encountering sea ice. Source data is Japan Meteorological Agency (JMA) maps provided in raster format without georeferencing, and National Snow and Ice Data Center (NSIDC) maps provided in GeoTIFF format with georeferencing. The module implements an algorithm that allows to calculate the probability of ice occurrence of a given concentration interval at each point (pixel) of a raster map, and then build polygonal vector maps in SHP-format based on the array of probabilities. The algorithm for constructing polygonal objects provides for a sequential enumeration of all horizontal adjacent pairs of elements of the array of probabilities, followed by determining the boundaries of the polygon. Detection of the first points of the polygon boundary allows to start a cyclic search for adjacent points that meet the boundary condition and creating a complete list of points of a closed polygon. Similarly, all other polygons are searched within the water area specified by the color mask. At the last stage, the lists of Cartesian coordinates of points are converted into geographical coordinates. Based on them, polygonal objects are formed in the SHP-file format. Polygon features define areas of probability of encountering ice that belong to the same interval, and include numeric attributes with values for the boundaries of the probability intervals. The generated vector maps allow further data analysis in GIS applications. The developed software was used to build maps of the probability distribution of encountering ice in the waters of the Far Eastern seas.

Gas hydrate dissociation by depressurization along with ice occurrence and sand migration

The extraction efficiency and safety of hydrate reservoirs are important for the industrialization of hydrate energy production. In this connection, various depressurization schemes with different amplitudes, rates and modes have been tried in field production tests. In this work, production profiles of laboratory-scale hydrate-bearing sediments were simulated through different depressurization schemes at a constant ambient temperature of 275.45 K. The results show that there are the freezing - melting behavior (FMB) and isothermal stage in the system with the depressurization amplitude (ΔP) range of 1.27–2.67 MPa, but not in the system with a ΔP of 0.83 MPa. In addition, the lower final outlet pressure and the higher depressurization rate increase the ice content and the ice duration of the system. Based on this, the linear equation of beginning freezing time of system (each observation point) can be obtained by fitting. According to the maximum ice content of system (0.06–3.56 E−4m2) under deep depressurization mode, the function of ice content of the system with the ΔP and the production time can be obtained. Moreover, the effects of FMB and sand detaching behavior were analyzed on pore fluid migration. FMB can temporarily block 0–66.56% of the migration space of pore fluid (MSPF). It can be revealed that the pore water velocity of observation points in the absence of FMB increases first and then steadily declines over time. But the former stage due to FMB can be divided into a slight decrease/increase and a sharp increase. Meanwhile, it can be found from the sediment components that the behaviors of skeleton sand detaching and hydrate dissociation can expand the MSPF, with contribution percentages of 0–13.49% and 86.51–100%, respectively. Finally, the high depressurization rate can advance the peak of gas production and water production by 14–22 min and 13–17 min, respectively. The high ΔP can improve the production rate peaks of gas and water about 34–59% and 17.4–41%, respectively, and advance the peak of sand production by 19–60 min. The findings of this work clearly illustrate the importance of the depressurization scheme for the extraction of hydrate resources and provide a basis for the best production scheme.

Conditions favorable for secondary ice production in Arctic mixed-phase clouds

Abstract. The Arctic is very susceptible to climate change and thus is warming much faster than the rest of the world. Clouds influence terrestrial and solar radiative fluxes and thereby impact the amplified Arctic warming. The partitioning of thermodynamic phases (i.e., ice crystals and water droplets) within mixed-phase clouds (MPCs) especially influences their radiative properties. However, the processes responsible for ice crystal formation remain only partially characterized. In particular, so-called secondary ice production (SIP) processes, which create supplementary ice crystals from primary ice crystals and the environmental conditions that they occur in, are poorly understood. The microphysical properties of Arctic MPCs were measured during the Ny-Ålesund AeroSol Cloud ExperimENT (NASCENT) campaign to obtain a better understanding of the atmospheric conditions favorable for the occurrence of SIP processes. To this aim, the in situ cloud microphysical properties retrieved by a holographic cloud imager mounted on a tethered balloon system were complemented by ground-based remote sensing and ice-nucleating particle measurements. During the 6 d investigated in this study, SIP occurred during about 40 % of the in-cloud measurements, and high SIP events with number concentrations larger than 10 L−1 of small pristine ice crystals occurred in 4 % of the in-cloud measurements. This demonstrates the role of SIP for Arctic MPCs. The highest concentrations of small pristine ice crystals were produced at temperatures between −5 and −3 ∘C and were related to the occurrence of supercooled large droplets freezing upon collision with ice crystals. This suggests that a large fraction of ice crystals in Arctic MPCs are produced via the droplet-shattering mechanism. From evaluating the ice crystal images, we could identify ice–ice collision as a second SIP mechanism that dominated when fragile ice crystals were observed. Moreover, SIP occurred over a large temperature range and was observed in up to 80 % of the measurements down to −24 ∘C due to the occurrence of ice–ice collisions. This emphasizes the importance of SIP at temperatures below −8 ∘C, which are currently not accounted for in most numerical weather models. Although ice-nucleating particles may be necessary for the initial freezing of water droplets, the ice crystal number concentration is frequently determined by secondary production mechanisms.