Characteristics and recent dynamics of thermo-erosional features in small catchments of Arctic Siberia

Thermal erosion is a prominent type of permafrost degradation that can lead to rapid changes in ice-rich permafrost landscapes. The process and its resulting landforms such as thermo-erosional gullies are reported to become increasingly active and widespread. (Re-)Activation of thermal erosion impacts the hydrological regime of affected landscapes and alters the biogeochemical composition of associated surface waters. Our study aims at assessing current rates and mechanisms of thermal erosion in small ice-rich permafrost catchments of Arctic Siberia. We investigated thermoerosional features in three different areas in and around the Lena River Delta that represent differing geomorphological, lithological and geocryological settings. We used a combination of field measurements, remote sensing methods including tacheometry, DGPS, and UAV surveys and subsequent GIS analyses to 1) quantify the morphometry of thermo-erosional landforms, 2) quantify the spatial extent of current thermo-erosional activity, and 3) quantify areal changes in activation and stabilization of thermal erosion over recent years to decades. Further data on snow depth and distribution in the gullies and valleys as well as hydrological and hydrochemical data of the associated streams aided the interpretation of observed spatial differences in thermal erosion rates and the development of active versus stabilized zones as well as their impacts on headwaters

The Influence of Climate Warming on the Hydrological Regime of Thermokarst Lakes in the Subarctic (Chukotka, Russia)

Using remote methods and materials for meteorological observations, climate changes and the area of 36 thermokarst lakes located in the Anadyr lowland in Chukotka over a 65-year period were analyzed. More than 20 lakes were studied by field methods. With an increase in the average annual air temperature by 1.8°C and an increase in the amount of annual precipitation by 135 mm, the total area of the lakes mirror decreased by 24%. Cryogenic processes have had a significant impact on the decrease in the water quantity of lakes. Thermal erosion in drainage channels has led to multiple discharges of water in abnormally warm years. The heaving of permafrost in the coastal zone affected the reduction of the lake catchment area. If the trends of climate change continue, further drainage of large lakes and an increase in the number of small sag pond is expected in the next 25 years

ВОЗМОЖНОСТИ ОЦЕНИВАНИЯ БАССЕЙНОВОЙ ТРАНСПИРАЦИИ НА ОСНОВЕ ИЗМЕРЕНИЯ СТВОЛОВОГО СОКОДВИЖЕНИЯ: ПОСТАНОВКА ЗАДАЧИ

Study of seasonal dynamics and evapotranspiration volume of forested catchments (mainly forest stand transpiration) is the relevant objective for fundamental knowledge and practical applications. However, there are many difficulties: labor efforts of direct observations, many factors affecting against each other, observational data scaling and so on. As a result, evapotranspiration during hydrological modeling is determined by the leftover principle and simplified techniques, leading to wrong representation of water balance structure. The presented article deals with the first results of our research group focused on setting up field measurements of xylem sap flow using trunk sap flow measuring sensors as well as development of sap flow assessment methods for individual trees and whole catchment. The investigations were performed for mixed coniferous-broad leaved forests at the territory of the Central Sikhote-Alin’ within Verkhneussuriyskiy biogeocenotical station of FSC of the East Asia Terrestrial Biodiversity FEB RAS. This site is used for water balance measuring surveys from 2011. Sap flow was measured continuously during June-October of 2019 on one of the local dominant tree species. Apparently, such investigations are novel for the Russian Far East region. It is expected that direct sap flow measurements for individual trees refinement methods, data scaling and its integration to the hydrometeorological observations will help to make a comprehensive analysis of catchments water balance and to integrate measured data into hydrological models.Изучение сезонной динамики и объемов суммарного испарения лесных водосборов (главным образом транспирации древостоев) является актуальнейшей задачей как в фундаментальном, так и прикладном аспектах. Ее решение связано с рядом сложностей: трудоемкость прямого наблюдения, наличие большого количества влияющих друг на друга факторов, необходимость распространения данных точечных измерений на площадь и многие другие. Это приводит к тому, что при моделировании водного баланса речных бассейнов испарение определяется по упрощенным схемам, остаточному принципу, что ведет к неправильному отражению структуры водного баланса. Настоящая статья представляет первые результаты усилий инициативного коллектива исследователей, направленных на постановку экспериментальных измерений ксилемного потока с использованием современных датчиков стволового сокодвижения, а также развития методов оценки транспирации как отдельных деревьев, так и бассейновой транспирации на основе этих данных. Исследование проведено на территории смешанных хвойно-широколиственных лесов Центрального Сихотэ-Алиня в пределах экспериментального водосбора, входящего в состав Верхнеуссурийского биогеоценотического стационара ФНЦ Биоразнообразия ДВО РАН, на котором рабочей группой возобновлены воднобалансовые работы в 2011 г. и в настоящее время являются уже постоянными. Регистрация стволового сокодвижения выполнялась в период с июня по начало октября 2019 года на одном из доминантных видов местного растительного сообщества. В Дальневосточном регионе России работы такого плана, по-видимому, проведены впервые. Предполагается, что отработка методов оценки прямых измерений транспирации на уровне отдельных деревьев, попытка пространственной генерализации на территорию топологического масштаба и вовлечение полученной информации в комплекс гидрометеорологических наблюдений позволят выполнить исчерпывающий анализ водного баланса в пределах малого речного бассейна и интегрировать поток измеряемых данных по испарению в гидрологические модели. &nbsp

Water tracks in the lower Lena River basin

In the permafrost regions, where water filtration zone is limited by the shallow active layer, the surface flow forms a network of hollows, called «water tracks», oriented along the slope gradient. Water tracks are clearly distinguished on satellite images, but poorly defined in the field. The pattern of the water tracks network depends on geomorphological position, permafrost and geological conditions and dominant cryogenic processes. Surface flow could occur in the water tracks during the snowmelt and heavy rains, when the soil is entirely frozen or fully saturated by water. In dry periods, the water tracks form retention zones due to low filtration rates and significant capacity of thawed soil beneath the troughs. Our study of water tracks in the north-western Yakutia showed the changes of their morphology from upstream towards downstream. The water levels in the water tracks have a pronounced diurnal course in reverse phase to the water temperature variation. They are related to diurnal ground thawing dynamics. Hydrology of water tracks depends on the peat thickness, active layer properties and lithology. Water tracks formed by rubble rocks respond to a storm event with rapidly increasing water level. The deeper thawing layer, the smoother water levels rise and decrease

Comparing the Runoff Decompositions of Small Experimental Catchments: End-Member Mixing Analysis (EMMA) vs. Hydrological Modelling

This study is focused on the comparison of streamflow composition simulated with three well-known rainfall–runoff (RR) models (ECOMAG, HBV, SWAT) against hydrograph decomposition evaluated with End-Member Mixing Analysis (EMMA). In situ observations at two small mountain testbed catchments located in the south of Pacific Russia are used. All applied RR models and EMMA analysis demonstrate that two neighboring catchments disagree significantly on the mutual dynamics of the runoff sources. The RR models' benchmark test is based on proximity to EMMA hydrograph composition. Different aggregation intervals (season, month, and pentad) were applied to find a reasonable generalization period ensuring the clarity of results. ECOMAG is most conformable to EMMA outcome; HBV reflects flood events well enough; SWAT exhibits distinctive behavior compared to the other models. It is shown that, along with standard efficiency criteria of simulated and observed runoff proximity, EMMA analysis might provide useful auxiliary information for the validation of modelling results

The Effect of Atmospheric Pressure Variations on the Suprapermafrost Groundwater Level and Runoff of Small Rivers in the Anadyr Lowlands, Northeast Russia

The present-day models of the hydrological regime of soils and river basins do not include a hypothesis regarding the effect of atmospheric pressure on hydrological processes (baric effect), which is assumed negligible. However, their manifestations are likely, considering the mechanical and hydrophysical properties of shallow peat-bog soils (plasticity and elasticity, high moisture-retention capacity, the ability to swell and shrink) and the important role of undecomposed plant remains. The effect of atmospheric pressure variations on level changes in a suprapermafrost aquifer was detected using field and laboratory experiments in shallow peat and peaty tundra soils in the Anadyr Lowlands, Northeast Russia. One can see this effect in the runoff regime of 1st–4th orders streams. The manifestations of this phenomenon can differ, and in particular, they can be directed oppositely. The changes in the level and storage of suprapermafrost gravitational water could be caused only by synchronous (in phase opposition) changes in capillary water fringe above the groundwater table. To explain the observed phenomena, a conceptual model is developed based on the analysis of the balance of forces and water balance in a system of elastic capillaries. Not being complete and perfect, the model reproduces qualitatively the main observed cases of the response to air pressure changes, proving the effect itself, and suggests the likely localization of its mechanisms. A shallow suprapermafrost groundwater table in contact with the peat bottom, as well as incomplete (below the full moisture capacity) water saturation of peat soil horizons, appear to be circumstances of the baric effect on tundra shallow subsurface aquifers. Favorable conditions for the baric effect in a soil profile include a high elasticity of peat-soil matrix, high and variable values of porosity and water yield of peat and moss cover, and, at the catchment scale, a high proportion of coverage by these types of soils. A full-scale study of a mechanism of baric effect on a suprapermafrost tundra aquifer requires numerous laboratory and field experiments, that must be much better equipped than presented in our study. It is also welcomed alternative hypotheses regarding the aquifer water level response to changes in air pressure if the observed macroscopic effects at any alternative occurrence could be quite similar

The Effect of Atmospheric Pressure Variations on the Suprapermafrost Groundwater Level and Runoff of Small Rivers in the Anadyr Lowlands, Northeast Russia

The present-day models of the hydrological regime of soils and river basins do not include a hypothesis regarding the effect of atmospheric pressure on hydrological processes (baric effect), which is assumed negligible. However, their manifestations are likely, considering the mechanical and hydrophysical properties of shallow peat-bog soils (plasticity and elasticity, high moisture-retention capacity, the ability to swell and shrink) and the important role of undecomposed plant remains. The effect of atmospheric pressure variations on level changes in a suprapermafrost aquifer was detected using field and laboratory experiments in shallow peat and peaty tundra soils in the Anadyr Lowlands, Northeast Russia. One can see this effect in the runoff regime of 1st–4th orders streams. The manifestations of this phenomenon can differ, and in particular, they can be directed oppositely. The changes in the level and storage of suprapermafrost gravitational water could be caused only by synchronous (in phase opposition) changes in capillary water fringe above the groundwater table. To explain the observed phenomena, a conceptual model is developed based on the analysis of the balance of forces and water balance in a system of elastic capillaries. Not being complete and perfect, the model reproduces qualitatively the main observed cases of the response to air pressure changes, proving the effect itself, and suggests the likely localization of its mechanisms. A shallow suprapermafrost groundwater table in contact with the peat bottom, as well as incomplete (below the full moisture capacity) water saturation of peat soil horizons, appear to be circumstances of the baric effect on tundra shallow subsurface aquifers. Favorable conditions for the baric effect in a soil profile include a high elasticity of peat-soil matrix, high and variable values of porosity and water yield of peat and moss cover, and, at the catchment scale, a high proportion of coverage by these types of soils. A full-scale study of a mechanism of baric effect on a suprapermafrost tundra aquifer requires numerous laboratory and field experiments, that must be much better equipped than presented in our study. It is also welcomed alternative hypotheses regarding the aquifer water level response to changes in air pressure if the observed macroscopic effects at any alternative occurrence could be quite similar

L3 rootlet recurrent melanocytic schwannoma – case report and literature review

First described by Miller in 1932, melanocytic schwannoma (MS) (melanotic schwannoma, pigmented schwannoma) is a rare variation of peripheral nerve sheet tumours with ectodermal origin occurring predominantly in somatic, but also in the autonomic peripheral system with around two hundred cases in the literature. Predominantly benign tumours, MS are still imaging and pathological challenge and can be easily misdiagnosed with more aggressive peripheral nerve tumours.We report a case of melanocytic schwannoma on L3 sensory rootlet with systematic literature review of nearly 200 cases presented in intracranial, paraspinal region, thoracic, abdominal or pelvic cavities and skin. Two-thirds of cases are part of Carney complex.We present a case of a 61-year-old male with a 3-month history of low back pain, progressive numbness and stiffness in the right thigh, shin and knee, tibial and peroneal paresis causing gait disturbance and neurological claudication. MRI findings present “sand clock” type intradural extramedullary tumour formation with extension to the L3 rootlet through right L3-L4 foramen, hypointense on T2 and hyperintense on T1. Pathological diagnosis of sporadic type melanocytic schwannoma was made via immunohistological and ultrastructural analysis. Thirteen months after total resection there was clinical and MRI evidence of recurrence of the tumour. Total resection and radiosurgery was performed with a recurrence free period of 14 months.A gold standard for melanocytic schwannoma treatment is gross total surgical resection. Despite being considered benign tumours, MS have a local or metastatic recurrence of around 13%. MRI imaging in most of the cases is insufficient and only exhaustive pathological and immunohistological examination is the key to diagnosis. Need of postoperative radiation therapy is still controversial. For the first time, a criterion for postoperative adjuvant therapy was established

Microelements in river water of mountain-forest basins (Southern Russian Far East)

Актуальность: Изучение миграции растворенных химических элементов в составе речных вод в зоне их формирования в горно-лесных ландшафтах. Цель: выявление диапазонов концентраций микроэлементов в водах фоновых рек начальной гидрологической сети, определение вероятных путей их геохимической миграции. Объекты: река Правая Соколовка (система верховьев Уссури) и четыре ее притока. Методы. Концентрации микроэлементов и редкоземельных элементов определялись методом ICP-MS на приборе Agilent 7700 х (Agilent Techn., США). Содержание главных анионов (Cl-, SO42-, NO3-) определялось на жидкостном хроматографе Shimadzu LC 10Avp, главных катионов (Ca2+, Mg2+, K+, Na+) - на атомно-абсорбционном спектрометре Shimadzu AA 6800; растворенного органического углерода (РОУ) - с помощью ТОС-анализатора (Shimadzu TOC-VCPN). При обработке количественных данных использовали статистические методы анализа. Результаты. Комплексные гидрохимические исследования на пяти модельных водосборах, расположенных в среднегорном поясе Южного Сихотэ-Алиня, проведены в теплый период 2012, 2019 и 2020 гг. В пробах речной воды были определены основные компоненты химического состава, содержание «растворенных», а по существу суммы растворенных и коллоидных форм (фракция <0,45 мкм) микроэлементов. Анализ более 80 проб позволил оценить пространственно-временную вариабельность измеренных концентраций микроэлементов и установить вероятные факторы, способствующие их переносу в пределах малых водосборов с различной ландшафтной структурой. Сравнение полученных средних концентраций микроэлементов с соответствующими величинами условно чистых рек Сихотэ-Алинской горной области и мировым стоком показало сходный уровень их содержания. В целях установления совместно мигрирующих элементов и возможных компонентов, контролирующих поступление микроэлементов в речные воды, был проведен сопряженный корреляционный анализ массива данных их макрокомпонентного и микроэлементного состава. Установлено, что концентрации слабоподвижных (Al, Sc, Ga, Y, Zr, Hf, редкоземельных элементов), некоторых катионогенных (Fe, Mn, Co) и анионогенных (Se, V, Ge) микроэлементов в речных водах прямо связаны с содержанием растворенного органического углерода. Это предполагает, как одновременную миграцию органического углерода и связанных с ним элементов c водосборной площади во время выпадения интенсивных дождей, так и нахождение некоторой доли элементов в составе комплексов с органическими компонентами. Предварительный анализ особенностей режима увлажнения и ландшафтной структуры водосборов выявил тенденции межгодовой изменчивости растворенных форм Fe и Al в водах рек, дренирующих водосборы с различной структурной организацией лесных экосистем. Показано, что распространение в бассейнах горно-таежных почв, сформированных под темнохвойными лесами, обусловливает наименьшую сезонную и межгодовую изменчивость «растворенных» форм типоморфных элементов, а также их более стабильную связь с органическим углеродом. В случае доминирования в бассейнах хвойно-лиственных экосистем сезонная и межгодовая изменчивость содержания «растворимых» форм Fe и Al, проходящих через фильтр 0,45 мкм, выражена наиболее контрастно. Концентрация Fe и Al во фракции <0,45 мкм обратно пропорциональна кислотности речных вод, вариабельность которой связана с процессами аккумуляции и вымывания органических веществ из почвы.Relevance: study of the migration of chemical elements from mountain-forest ecosystems into rivers in the runoff formation zone. Purpose: assessment of microelements content and the ranges of their variability in the water of background streams at mountainous headwaters, and detecting the probable pathways and mechanisms of their geochemical migration. Objects: Pravaya Sokolovka R. (the Ussuri R. system) and its four tributaries. Methods. The concentrations of trace elements and rare earth elements were determined by ICP-MS Agilent 7700 x (Agilent Techn., USA). The content of the main anions (Cl- , SO42 - , NO3 - ) was determined on a Shimadzu LC 10Avp liquid chromatograph, the main cations (Ca2+ , Mg2+, K+ , Na+ ) - on a Shimadzu AA 6800 atomic absorption spectrometer; dissolved organic carbon (DOC) - using a TOC analyzer (Shimadzu TOC-VCPN). When processing quantitative data, the standard statistical methods of analysis were used. Results. During the warm period in 2012, 2019 and 2020, there were carried out the integrated hydrochemical studies at five research catchments located in the middle mountain belt of the Southern Sikhote-Alin. In river water samples, the main chemical components and the microelements dissolved forms were determined. The analysis of about 80 samples made it possible to assess the spatialtemporal variability of the measured concentrations of trace elements and to establish the probable factors driving their migration in small river catchments differing in landscape patterns. A comparative analysis of found trace elements concentrations showed their similar relevant values for conventionally clean rivers of the Sikhote-Alin mountain country and over the world. To reveal possible mechanisms of microelements migration into rivers, the authors accomplished a conjugate correlation analysis for the dataset of macrocomponent and microelement composition of the river water. We assumed that during rainfall events, the leaching of dissolved organic carbon and related elements from soil cover is the main mechanism for concentrating low-mobile (Al, Sc, Ti, Cr, Ga, Y, Zr, Hf, and Rare Earth Elements), some heavy (Fe, Mn, and Co), and anion-generating (Cr, Se, V, and Ge) trace elements. This suggests the migration of organic carbon and related elements from the catchment during heavy rains and the simultaneous presence of a certain proportion of elements in the composition of complexes with organic matter. A preliminary analysis of the peculiarities of the moistening regime and the landscape structure of watersheds revealed trends in the interannual variability of dissolved forms of Fe and Al in the rivers draining watersheds with the different structural organization of forest ecosystems. It is shown that the distribution of mountain taiga soils in river basins determines the lowest seasonal and interannual variability of dissolved forms of typomorphic elements, as well as their more stable relationship with organic carbon. In the case of dominance of coniferous-deciduous ecosystems in a catchment, the content of Fe and Al soluble forms depends on river water acidity, which varies associated with the processes of organic substances accumulation and leaching from the soil