12 research outputs found
Retrieval procedure of effective conductivity for plasmonic resonant anisotropic metasurface
No full textMorphometric parameters of ice hummocks and stamukhas from the data of expeditionary research in the northwestern part of the Caspian Sea
No full textTHE STATISTICAL MODEL OF PRESSURE RIDGE MORPHOMETRY ON THE NORTHEAST SHELF OF SAKHALIN ISLAND
No full textThe work presents characteristics on geometry and inner structure of ice ridges investigated at offshore the northeast coast of SakhalinIsland. A formula was obtained which allows one to calculate the ice ridge keel depth by the height of its sail. Plots of the probability distribution density for ice ridge characteristics are given. A model of morphometry of a mean statistical ice ridge was constructed, and its mass is determined. Factors influencing the hydrostatic ice ridge equilibrium are considered
Типизация полей атмосферного давления в морях Лаптевых и Восточно-Сибирском
Get PDFThe need for classifying surface atmospheric pressure fields over the Arctic seas arose as a method was being developed for predicting the characteristics of discontinuities (leads) in the sea ice cover. Wind, which is determined by the atmospheric pressure field, acts on the ice cover and causes it to drift. Leads are formed in the ice cover due to the irregularity of ice drift. Ice drift can be caused by several factors, such as skewed sea level, tidal waves and currents. However, the main cause of ice drift in the Arctic seas is wind. Each typical field of surface atmospheric pressure corresponds to a certain field of leads in the ice cover. This makes it possible to predict the characteristics of leads in the ice cover by selecting fields similar to predictive fields of atmospheric pressure based on archived data.The variety of atmospheric pressure fields makes it difficult to find an analogue to a given field by simply going through all the corresponding data available in the electronic archive. Classification of atmospheric pressure fields makes it possible to simplify the process of selecting an analogue.To develop the classification, we used daily surface pressure maps at 00 hours GMT for the cold seasons (from mid- October to the end of May) 2016–2021. The atmospheric pressure fields, which were similar in configuration, and hence the wind fields, belonged to the same type. In total, 27 types were identified, applicable both to the Laptev Sea and the East Siberian Sea. Within one type, a division into subtypes was made, depending on the speed of the geostrophic wind.The wind intensity was estimated by the number of isobars multiples of 5 mb on the surface atmospheric pressure map. All the surface pressure fields observed over the waters of the Laptev and East Siberian Seas over the past 5 years have been assigned to one of the types identified using cluster analysis. Each type of atmospheric pressure within the framework of the forecasting method being developed is supposed to correspond to a field of discontinuities in the ice cover.Поле атмосферного давления определяет направление ветра и его скорость. Ветер, воздействуя на ледяной покров, вызывает его дрейф. Неравномерность поля дрейфа является причиной образования разрывов в ледяном покрове. Каждому типовому полю атмосферного давления соответствует определенное поле разрывов в ледяном покрове. Подбор для прогностических полей атмосферного давления аналогичных типовых полей по архивным данным дает возможность прогнозировать характеристики разрывов в ледяном покрове. Для формализации подбора аналогов была разработана типизация полей атмосферного давления в морях Лаптевых и Восточно-Сибирском по ежесуточным синоптическим картам за холодные сезоны 2016–2021 гг. Всего было выделено 27 типов, которые разделены на подтипы в зависимости от интенсивности ветра
Determination of the Predominant Orientation of Cracks in Ice Cover of the Laptev Sea from the Ice Drift Data
No full textThe paper shows that in order to solve the problem of predicting the predominant orientation of cracks in ice covering the Laptev Sea, when the satellite information is absent, the orientation of cracks in ice cover can be calculated using data on the ice drift in the Sea. We have selected 200 satellite images made in both visible and infrared spectral bands allowing to obtain actual data on ice cracks in the Laptev Sea for seasons 2016–2021, and then calculated the predominant orientation of them using data on the OSI SAF ice drift for the date of each image as well as for several previous days. Results obtained were compared with actual modal orientations of the cracks and with characteristics of the atmospheric pressure fields in these days. It was found that selecting of initial ice drift data should be done with regard for the intensity of air flows, the invariability or constancy of the direction of air flows over the sea aquatory during several days, and the presence of a cyclone centered over the sea area. An algorithm has been developed for automatic selection of a date when the ice drift can be most likely accompanied by formation of cracks on the day under consideration, and calculation of predominant orientation of cracks should be made exactly on that day. The selected data on ice drift serve as a basis for calculating. It was revealed also that with the difference in the types of intensity of air flows in the northern and southern parts of the Laptev Sea, the developed algorithm for determining the date of ice drift should be applied to each part of the sea separately. The number of squares of the Laptev Sea grid in which the calculated orientation of cracks corresponded to its actual meaning with an established permissible error of 30° has been determined. The ratio of this number to the total quantity of grid squares (skill score) was equal to 69% on the average. The skill score exceeded 70% in 46 percent of the cases. The skill score falls below 60% in only 16 percent of the cases, with minimum value of 50%
Comprehensive study of old hummocks in the Arctic Ocean
Get PDFIn May 2015, the old hummock located to the North of the Bennett island (the East Siberian Sea) was investigated using several methods, among which were water thermal drilling, tachometric and sonar surveys, underwater video recording, as well as techniques to determine the strength and physical properties of ice. It was found out that only a combination of different methods provides a way to correctly estimate the main morphometric characteristics of a large ice formation and to determine its volume and mass. Analysis of the internal structure of the hummock, obtained by the water thermal drilling with a record of the drilling rate on the logger, made it possible to reveal a composite character of the ice formation (the hummock consisted of two fragments – the large old one and the smaller first-year piece) and to estimate approximately its age (3–4 years). Comparison of the main morphometric characteristics of the old hummock with the average values of first-year hummocks, investigated in the same area and the time, showed that the old hummock had significantly greater geometric parameters: its volume and mass exceeded similar parameters of the average younger formation by factors 5.6 and 5.8, respectively. This significant difference allows suggestion that the reason is not the age but a composite structure of the old formation. The average thickness of the consolidated layer of the old hummock equal to 4.6 m is almost twice larger than similar parameter of a first-year hummock (2.33 m) while the average value of the thickness in the old part of the old hummock (5.22 m) is larger than that of a young one by the factor 2.2. Note also, that the old hummock is characterized by almost complete smoothness (impossible to separate individual blocks) and minimal porosity (1%) of its ice. The salinity and density of the ice composing the frontal part of the old hummock is much smaller than in first-year hummocks. The average density of ice in the old hummock, determined analytically from the buoyancy condition, was equal to 896 kg/m3, while the average density of ice in the first-year hummocks, determined from measurements, – 917 kg/m3
Comprehensive study of old ice ridges in the Arctic Ocean
No full textIn May 2015, a comprehensive study of an old ice ridge was carried out to the north of Bennett Island in the East-Siberian Sea with application of water thermal drilling, tachometric and sonar surveys, video survey by the underwater device and methods for determination of the ice strength and physical properties. It is shown that only a combination of different methods allows us to obtain a correct assessment of the main morphometric characteristics of a large ice feature and determine its volume and mass. An analysis of ice ridge internal structure parameters obtained by the method of water thermal drilling with the drilling rate record to a logger made it possible to reveal a composite character of the ice feature (the ice ridge consisted of a larger old fragment and a smaller first-year fragment) and approximately assess its age (3-4 years). A comparison of the main morphometric characteristics of an old ice ridge and the average values of first-year ice ridges, investigated in the same region at the same period of time showed the old ice ridge to have significantly greater geometric parameters. The old ice ridge volume and mass were greater compared to the average first-year ice ridge by 5.6 and 5.8 times, respectively. Such significant advantage of the old ice ridge is likely to be determined by the composite character of the ice feature rather than by its age. The average for the entire composite ice ridge thickness of the consolidated layer (4.6 m) is almost two-fold greater than the average thickness of the consolidated layer in the first-year ice ridges (2.33 m), and the average value of the consolidated layer in the ice ridge old part (5.22 m) is 2.2 times greater than in first-year ice ridges. An old ice ridge is characterized by an almost complete flatness (without any possibility to identify some separate blocks) and minimal sail porosity (1 %). The salinity and density of ice comprising the old ice ridge sail were much lower than in first-year ice ridges. The sail/keel ratio is greater on average in first-year ice ridges – 3.46 against 3.07 in the old ice ridge. The average ice density in the old ice ridge, determined analytically in accordance with the buoyancy conditions, was 896 kg/m3, and the average ice density in first-year ice ridges based on measurement data was 917 kg/m3
СТАТИСТИЧЕСКАЯ МОДЕЛЬ МОРФОМЕТРИИ ГРЯДЫ ТОРОСА НА СЕВЕРО-ВОСТОЧНОМ ШЕЛЬФЕ О. САХАЛИН
No full textThe work presents characteristics on geometry and inner structure of ice ridges investigated at offshore the northeast coast of SakhalinIsland. A formula was obtained which allows one to calculate the ice ridge keel depth by the height of its sail. Plots of the probability distribution density for ice ridge characteristics are given. A model of morphometry of a mean statistical ice ridge was constructed, and its mass is determined. Factors influencing the hydrostatic ice ridge equilibrium are considered.Приведены характеристики геометрии и внутренней структуры гряд торосов, исследованных на северо-восточном шельфе о. Сахалин. Получена формула, позволяющая рассчитать глубину киля гряды тороса по высоте его паруса. Даны графики плотности распределения вероятностей для характеристик гряды тороса. Построена модель морфометрии и определена масса среднестатистической гряды тороса. Рассмотрены факторы, влияющие на гидростатическое равновесие гряды тороса
Оценка возраста гряд торосов в замерзающих морях
Get PDFA method of estimating the ice ridge age proposed in the 1990s was analyzed and some disadvantages of this method were shown. Analysis of the ice thickness distribution in the ice ridges demonstrated that in many cases the average value of the thickness used in the above mentioned method did not correspond to the thickness of an ice floe of which the ice blocks were formed. The ice floe thickness is characterized by the modal value of the ice thicknesses. After the ice ridge has been formed the ice block thickness in its above-water part does not change while the thickness of the ice floe on which the ice ridge is located continues to increase. Our study has shown that the difference between thickness of the plane ice and the modal value of the ice block thickness may be used as a characteristic of the ice growth for the period of the ice ridge existence. This period can be determined by one of the calculation formulas at the known initial and final ice thickness. Calculation by formula of the ice growth thickness make possible to derive the date of ice ridge formation based on the average air temperatures. The updated method of estimating the time of ice ridge formation can be used for the ice-covered seas. Analysis of the estimated ice ridge ages showed a significant dependence of thickness of the minimal consolidated layer on the time of the ice ridge formation. A comparative analysis of (the) ages of ice ridges and the flexural strength of ice samples made it possible to determine important tendency - the increased ice strength in ice ridges of early formation. This allows us in further studies to derive a formula of relationship between an ice ridge age and a strength of its ice. In some cases the ice strength measurement in ice ridges can be replaced by a less laborious estimating of strength basing on data of the age.Предложен уточнённый способ определения возраста гряды торосов на основе сравнения модальной толщины блоков льда, слагающих её надводную часть, и толщины поля ровного льда, на котором расположена гряда в момент измерений. Возраст гряды торосов связан с толщиной консолидированного слоя. Установлена важная тенденция - для торосов раннего образования характерна повышенная прочность льда на изгиб
Расчёт преобладающей ориентации разрывов в ледяном покрове моря Лаптевых по данным дрейфа льда
Get PDFThe paper shows that in order to solve the problem of predicting the predominant orientation of cracks in ice covering the Laptev Sea, when the satellite information is absent, the orientation of cracks in ice cover can be calculated using data on the ice drift in the Sea. We have selected 200 satellite images made in both visible and infrared spectral bands allowing to obtain actual data on ice cracks in the Laptev Sea for seasons 2016–2021, and then calculated the predominant orientation of them using data on the OSI SAF ice drift for the date of each image as well as for several previous days. Results obtained were compared with actual modal orientations of the cracks and with characteristics of the atmospheric pressure fields in these days. It was found that selecting of initial ice drift data should be done with regard for the intensity of air flows, the invariability or constancy of the direction of air flows over the sea aquatory during several days, and the presence of a cyclone centered over the sea area. An algorithm has been developed for automatic selection of a date when the ice drift can be most likely accompanied by formation of cracks on the day under consideration, and calculation of predominant orientation of cracks should be made exactly on that day. The selected data on ice drift serve as a basis for calculating. It was revealed also that with the difference in the types of intensity of air flows in the northern and southern parts of the Laptev Sea, the developed algorithm for determining the date of ice drift should be applied to each part of the sea separately. The number of squares of the Laptev Sea grid in which the calculated orientation of cracks corresponded to its actual meaning with an established permissible error of 30° has been determined. The ratio of this number to the total quantity of grid squares (skill score) was equal to 69% on the average. The skill score exceeded 70% in 46 percent of the cases. The skill score falls below 60% in only 16 percent of the cases, with minimum value of 50%.Изложены основы алгоритма, позволяющего определить по последовательности полей приземного атмосферного давления за предшествующий период дату возникновения дрейфа льда, приведшего к деформациям в ледяном покрове и образованию существующей системы разрывов в море Лаптевых. Приведены результаты оправдываемости расчётной ориентации разрывов, полученной по данным фактического дрейфа льда на основе разработанного алгоритма
