Методика инвентаризации приледниковых озер архипелага Шпицберген

The paper discusses periglacial lakes, which were formed after the Little Ice Age due to the reduction of Spitzbergen (Svalbard) glaciation. A method for inventorying the periglacial lakes in Spitzbergen (Svalbard) is proposed based on the Norwegian Polar Institute cartographic materials and remote sensing methods. Such lakes have been formed due to deglaciation in Svalbard since the beginning of the 20th century after the Little Ice Age. Three morphological features of the periglacial lake were used as selection criteria: the lake is in contact with the glacier, the lake is located within the terminal moraine or borders on it, each of which is sufficient.As a result of the inventory, 705 periglacial lakes have been found in Spitzbergen (Svalbard). The largest number of lakes is located in the northeastern part of the archipelago, where the relief is poorly dissected. The largest clusters of lakes are found on the moraines of mountain-valley glaciers located on the warmer western coasts. The periglacial lakes were divided into 5 types: glacier-dammed lakes (19 %), lakes in contact with the glacier front (30 %), thermokarst lakes on the moraine (27 %), moraine-dammed lakes (15 %) and lakes in contact with the terminal moraine (9 %). The most numerous were periglacial lakes adjoining the glacier (about 50 %). Their total area is 162 km2 and accounts for 87 % of the total area of all periglacial lakes. The other half of the lakes have formed shores, and their transformation is likely to be much slower in the future. The quantitative ratio of lake types testifies to the active phase of the process of lake expansion in the archipelago. This ratio of lakes by groups can be a clear indicator of climate change in the archipelago.На основе картографических материалов Норвежского полярного института предложена методика поиска и инвентаризации приледниковых озер архипелага Шпицберген. Их формирование обусловлено дегляциацией, продолжающейся с начала ХХ в. Инвентаризация приледниковых озер архипелага позволяет фиксировать их текущие морфометрические характеристики для исследования климатических изменений в будущем.По состоянию на 2008–2012 гг. на архипелаге выявлено 705 приледниковых озер. Их распространение охватывает все области архипелага, где отмечено отступание ледников. В юго-западной (ЮЗ) и северо-западной (СЗ) частях архипелага в области горного оледенения большинство приледниковых озер сгруппировано на моренах горно-долинных ледников близ побережья. В восточной (В) части архипелага приледниковые озера рассредоточены вдоль границ покровного оледенения, и большинство из них имеют контакт с ледником. Согласно предложенным признакам местоположения и условию подпруживания ледником или мореной, было выделено 5 типов озер. Описание типов и средние характеристики приледниковых озер представлены для трех климатических районов Шпицбергена (В, СЗ, ЮЗ). Практически равное количество озер с формирующимися (ледяными) и уже сформированными берегами указывает на активную фазу процесса распространения и увеличения площади приледниковых озер на архипелаге

О формировании новых приледниковых озёр в бассейне залива Грёнфьорд (Шпицберген) в 1938–2010 гг.

Based on remote sensing and field methods, the state of the glacial lakes located in the Grønfjord Bay basin, Svalbard, was assessed for 2008–2010. New lakes were formed due to the retreat of the mountain-valley glaciers of the Nordenskiöld Land and the formation of moraine-ridge topography. According to the 2008–2010 aerial survey data, 111 glacial lakes were identified in the basin area. Most of the new lakes were formed on the moraines of the large mountain-valley glaciers Vestre and Austre Grønfjordbreen, Brydebreen, Skavlefjellbreen, and Tungebreen. The total area of the glacial lakes is 2.047±0.001 km², 84% of their total area belongs to the two largest lakes Bretjørna and Stemmevatnet. The rest of the lakes in the territory are small, from 20 to 330 m in length, and shallow. The estimation of the volume of water in the lakes was based on field measurements of the depths of 26 lakes and the correlation found. The total volume of water is 24.1 million m³, which is comparable with the value of annual glacial runoff in the basin.С помощью картографического сервиса Норвежского полярного института (toposvalbard) получены данные об озёрах в бассейне залива Грёнфьорд. Всего на водосборе на 2008–2010 гг. обнаружено 134 озера, среди них 111 – новые приледниковые озёра, которые образовались в связи с сокращением ледников с начала ХХ в. Подавляющее большинство приледниковых озёр появилось на территории морен крупных горно-долинных ледников – Западный и Восточный Грёнфьорд, Тунге и Скавле. Оценены суммарная площадь, объём озёр на водосборе и плотность распределения приледниковых озёр на площади морен. С 1938 до 2010 г. суммарная площадь всех озёр увеличилась в 4 раза

Исследование ледникового стока рек в бассейне залива Грён-фьорд (Западный Шпицберген)

The melting of glaciers in the Arctic archipelagoes provides glacier runoff, which must be considered when assessing river flow. Glacial runoff, as a component of the total river flow, directly affects the thermal and ice conditions of the bays, the productivity and species composition of the marine biota. Also, this process is broadly related to the livelihoods of the Arctic villages. Furthermore, it acts as the important factor for the development of transport and tourism. Melted water of Svalbard glaciers is a significant contribution in total runoff of the local rivers. The issue of this study is to assess this contribution. Grønfjord Bay was selected for assessment because of the fact of regular measurements of water discharge in the river estuaries from June to October. Among 7 rivers flowing into the bay, 6 have glacial runoff. Despite the fact that only small mountain glaciers are common in this area, its melting largely determines the water regime of the rivers. The value of the glacier runoff in Grønfjord Bay was calculated based on an estimation of the glaciers melting by average summer air temperature in 2017 and 2018. Comparison of the amount of glacial and total flow was carried out on the rivers flowing into the Grønfjord Bay.The comparative analysis of the glacial and total river flows size along the 6 rivers of the Grønfjord Bay: Grøndalselva, Grønfjorddalselva, Bretjørna, Aldegonda, Brydebekken, Vasstakelva showed significant differences in the glacier runoff content depending on the area of glaciation in the catchment of rivers. The content of glacial runoff in the total freshwater discharge by rivers into the bay in 2017 and 2018 vary from 20 to 90 %. The largest glacier runoff is observed on the Bretjørna river — 90 %, the Grøndalselva, Brydebekken and Vasstakelva have the smallest glacier runoff — 20 %. The average total glacial runoff of the rivers varied from 41 to 53 % of the total discharge of the rivers of the gulf.Таяние ледников на территории арктических архипелагов обеспечивает ледниковый сток, который необходимо учитывать при оценке речного стока. Целью данной работы является оценка доли ледникового стока в общем стоке рек, впадающих в залив Грён-фьорд. Для расчета количества стока ледников были использованы данные о средней летней температуре воздуха в 2017 и 2018 гг. Сравнение количества ледникового и общего стока было проведено на реках, впадающих в залив Грён-фьорд, где регулярно измеряется расход воды в устьях рек с июня по октябрь. Сравнительный анализ размеров ледниковых и суммарных речных потоков по шести рекам залива Грён-фьорд: Грён, Грён-фьорд, Брехьёрна, Альдегонда, Брюде, Васстак — показал существенные различия в доле ледникового стока в зависимости от площади оледенения в водосборах рек. Доля ледникового стока в общем объеме стока пресной воды реками в залив в 2017 и 2018 гг. колебалась от 20 до 90 %. Средний суммарный ледниковый сток рек колебался от 41 до 53 % от общего стока рек залива

Внутренняя дренажная сеть и характеристики подледникового стока ледника Альдегонда (о. Западный Шпицберген)

The polythermal Aldegondabreen is one of the most widely studied glaciers of the Nordenskjöld Land (Svalbard). However, the structure of its internal drainage network remains poorly understood. In order to determine the position and hydro-chemical characteristics of the surface and internal drainage channels of the glacier complex studies were carried out including ground penetrating radar (GPR) measurements and hydrological surveys. The GPR profiling performed in 2018–2020 identified four channels of internal drainage network, two of which are found along the northern side of the glacier in the area of cold ice and are subglacial. The other two are located in the area of temperate ice along the southern side of the glacier and are englacial, stretching at the cold-temperate surface. At the outlet grotto, the subglacial waters have a bicarbonate-calcium composition and low salinity (electrical conductivity 30–40 μS/cm), inherited from the surface meltwater streams that enter the moulins in the upper part of the glacier. No noticeable increase in mineralization occurs during the movement of the flow along the glacier bed. The englacial channels’ waters at the outlet grotto have the same bicarbonate-calcium composition but a higher salinity (electrical conductivity 100 μS/cm), which we attribute to the filtration through the rocks of the riegel near the Aldegonda terminus, or, alternatively, to the influx of the groundwater at the same spot. Measuring the hydrochemistry of the Aldegonda river tributaries both on the glacier’s surface, at the grottos and on the moraine in the valley made it possible to identify the zone of enrichment of the main volume of the low-mineralization glacial meltwater of bicarbonate-calcium composition by the high-mineralization (electrical conductivity up to 760 μS/cm) groundwater of sulphate-calcium composition coming from the springs on the riegel in front of the glacier’s terminus in the central part of the Aldegonda Valley. Presumably, the springs are fed by the deep filtration of melted glacial waters along the Aldegonda subglacial talik.С целью определения положения и гидрохимических характеристик поверхностных и внутренних дренажных каналов ледника были выполнены комплексные исследования, включавшие детальное георадиолокационное профилирование и гидрологическую съемку. Проанализированы материалы предшествующих работ по изучению дренажной сети и подледникового стока. По данным георадиолокации сделаны выводы о строении внутренней дренажной сети ледника, согласно которым выделены основные каналы движения талых вод: 2 подледниковых в области холодного льда и 2 внутриледниковых вблизи области теплого льда. Выдвинуты и обоснованы предположения об области питания внутриледниковых каналов в верховьях ледника и их дренировании в местах переуглублений. Показано изменение электропроводности и гидрохимического состава подледниковых выходов и реки Альдегонды на всем ее протяжении. Выявлена зона обогащения слабоминерализованных талых ледниковых вод гидрокарбонатно-кальциевого состава сильноминерализованными подземными водами сульфатно-кальциевого состава, поступающими из источников на ригеле перед фронтом ледника в центральной части долины реки Альдегонды

Лёд и снег озера Стемме (о. Западный Шпицберген) зимой 2019/20 г.

The results of observations and modeling of the formation of the snow-ice cover of Lake Stemme (West Svalbard Island) in winter 2019/20 are presented. The main information was obtained by two radar (GPR) survey, performed on the floating ice of the Lake on March 12 and April 22 of 2020. Authors believe that probably these observations were the first ones on the Lake. The use of the radar made it possible to obtain data on the dynamics of the thickness of the layers of snow and ice cover, the so-called “snow ice” which is formed when the boundary between snow and ice was submerged under water. During the time between records, the thickness of the last “snow ice” increased two to three times, i.e., from units to the first tens of cm, and it spread to the entire deep-water part of the Lake area. In addition, analysis of high-precision positioning of the radar records revealed a significant deflection in the ice surface in the central part of the Lake under the influence of snow load and the decreasing level of the reservoir. The calculations of the thermodynamics of the floating ice cover have shown that its thickening occurs as a result of the processes of congelation and isostatic ice formation, replacing each other at its lower and upper boundaries, respectively. At the same time, the formation of “snow ice” violates the characteristic feature of decreasing of ice thickness with growth of the snow thickness, which significantly influences on the thermal and mass balance of the Lake snow-ice cover. Results of calculations of the ice cover deformation did show that it takes place not only due to the elastic, but also to the viscous properties of ice, and it is concentrated in a narrow coastal zone. The maximum radial stress is reached at a distance of several meters from the shore, where a circular crack parallel to the shoreline is formed. Such a crack is formed at all ice thicknesses at about the same distance from the shore.Представлены и проанализированы результаты комплексных наблюдений снежно-ледяного покрова оз. Стемме (о. Западный Шпицберген) зимой 2019/20 г. Полевые данные дополнены результатами моделирования, описывающими особенности его нарастания и деформации

SARS-CoV-2 B.1.617.2 Delta variant replication and immune evasion

The B.1.617.2 (Delta) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first identified in the state of Maharashtra in late 2020 and spread throughout India, outcompeting pre-existing lineages including B.1.617.1 (Kappa) and B.1.1.7 (Alpha)1. In vitro, B.1.617.2 is sixfold less sensitive to serum neutralizing antibodies from recovered individuals, and eightfold less sensitive to vaccine-elicited antibodies, compared with wild-type Wuhan-1 bearing D614G. Serum neutralizing titres against B.1.617.2 were lower in ChAdOx1 vaccinees than in BNT162b2 vaccinees. B.1.617.2 spike pseudotyped viruses exhibited compromised sensitivity to monoclonal antibodies to the receptor-binding domain and the amino-terminal domain. B.1.617.2 demonstrated higher replication efficiency than B.1.1.7 in both airway organoid and human airway epithelial systems, associated with B.1.617.2 spike being in a predominantly cleaved state compared with B.1.1.7 spike. The B.1.617.2 spike protein was able to mediate highly efficient syncytium formation that was less sensitive to inhibition by neutralizing antibody, compared with that of wild-type spike. We also observed that B.1.617.2 had higher replication and spike-mediated entry than B.1.617.1, potentially explaining the B.1.617.2 dominance. In an analysis of more than 130 SARS-CoV-2-infected health care workers across three centres in India during a period of mixed lineage circulation, we observed reduced ChAdOx1 vaccine effectiveness against B.1.617.2 relative to non-B.1.617.2, with the caveat of possible residual confounding. Compromised vaccine efficacy against the highly fit and immune-evasive B.1.617.2 Delta variant warrants continued infection control measures in the post-vaccination era

SARS-CoV-2 spike N-terminal domain modulates TMPRSS2-dependent viral entry and fusogenicity

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike N-terminal domain (NTD) remains poorly characterized despite enrichment of mutations in this region across variants of concern (VOCs). Here, we examine the contribution of the NTD to infection and cell-cell fusion by constructing chimeric spikes bearing B.1.617 lineage (Delta and Kappa variants) NTDs and generating spike pseudotyped lentivirus. We find that the Delta NTD on a Kappa or wild-type (WT) background increases S1/S2 cleavage efficiency and virus entry, specifically in lung cells and airway organoids, through use of TMPRSS2. Delta exhibits increased cell-cell fusogenicity that could be conferred to WT and Kappa spikes by Delta NTD transfer. However, chimeras of Omicron BA.1 and BA.2 spikes with a Delta NTD do not show more efficient TMPRSS2 use or fusogenicity. We conclude that the NTD allosterically modulates S1/S2 cleavage and spike-mediated functions in a spike context-dependent manner, and allosteric interactions may be lost when combining regions from more distantly related VOCs

Altered TMPRSS2 usage by SARS-CoV-2 Omicron impacts infectivity and fusogenicity

The SARS-CoV-2 Omicron BA.1 variant emerged in 20211 and has multiple mutations in its spike protein2. Here we show that the spike protein of Omicron has a higher affinity for ACE2 compared with Delta, and a marked change in its antigenicity increases Omicron’s evasion of therapeutic monoclonal and vaccine-elicited polyclonal neutralizing antibodies after two doses. mRNA vaccination as a third vaccine dose rescues and broadens neutralization. Importantly, the antiviral drugs remdesivir and molnupiravir retain efficacy against Omicron BA.1. Replication was similar for Omicron and Delta virus isolates in human nasal epithelial cultures. However, in lung cells and gut cells, Omicron demonstrated lower replication. Omicron spike protein was less efficiently cleaved compared with Delta. The differences in replication were mapped to the entry efficiency of the virus on the basis of spike-pseudotyped virus assays. The defect in entry of Omicron pseudotyped virus to specific cell types effectively correlated with higher cellular RNA expression of TMPRSS2, and deletion of TMPRSS2 affected Delta entry to a greater extent than Omicron. Furthermore, drug inhibitors targeting specific entry pathways3 demonstrated that the Omicron spike inefficiently uses the cellular protease TMPRSS2, which promotes cell entry through plasma membrane fusion, with greater dependency on cell entry through the endocytic pathway. Consistent with suboptimal S1/S2 cleavage and inability to use TMPRSS2, syncytium formation by the Omicron spike was substantially impaired compared with the Delta spike. The less efficient spike cleavage of Omicron at S1/S2 is associated with a shift in cellular tropism away from TMPRSS2-expressing cells, with implications for altered pathogenesis

Longitudinal analysis reveals that delayed bystander CD8+ T cell activation and early immune pathology distinguish severe COVID-19 from mild disease

The kinetics of the immune changes in COVID-19 across severity groups have not been rigorously assessed. Using immunophenotyping, RNA sequencing, and serum cytokine analysis, we analyzed serial samples from 207 SARS-CoV2-infected individuals with a range of disease severities over 12 weeks from symptom onset. An early robust bystander CD8+ T cell immune response, without systemic inflammation, characterized asymptomatic or mild disease. Hospitalized individuals had delayed bystander responses and systemic inflammation that was already evident near symptom onset, indicating that immunopathology may be inevitable in some individuals. Viral load did not correlate with this early pathological response but did correlate with subsequent disease severity. Immune recovery is complex, with profound persistent cellular abnormalities in severe disease correlating with altered inflammatory responses, with signatures associated with increased oxidative phosphorylation replacing those driven by cytokines tumor necrosis factor (TNF) and interleukin (IL)-6. These late immunometabolic and immune defects may have clinical implications

SARS-CoV-2 B.1.617.2 Delta variant replication and immune evasion

The B.1.617.2 (Delta) variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first identified in the state of Maharashtra in late 2020 and spread throughout India, outcompeting pre-existing lineages including B.1.617.1 (Kappa) and B.1.1.7 (Alpha)1. In vitro, B.1.617.2 is sixfold less sensitive to serum neutralizing antibodies from recovered individuals, and eightfold less sensitive to vaccine-elicited antibodies, compared with wild-type Wuhan-1 bearing D614G. Serum neutralizing titres against B.1.617.2 were lower in ChAdOx1 vaccinees than in BNT162b2 vaccinees. B.1.617.2 spike pseudotyped viruses exhibited compromised sensitivity to monoclonal antibodies to the receptor-binding domain and the amino-terminal domain. B.1.617.2 demonstrated higher replication efficiency than B.1.1.7 in both airway organoid and human airway epithelial systems, associated with B.1.617.2 spike being in a predominantly cleaved state compared with B.1.1.7 spike. The B.1.617.2 spike protein was able to mediate highly efficient syncytium formation that was less sensitive to inhibition by neutralizing antibody, compared with that of wild-type spike. We also observed that B.1.617.2 had higher replication and spike-mediated entry than B.1.617.1, potentially explaining the B.1.617.2 dominance. In an analysis of more than 130 SARS-CoV-2-infected health care workers across three centres in India during a period of mixed lineage circulation, we observed reduced ChAdOx1 vaccine effectiveness against B.1.617.2 relative to non-B.1.617.2, with the caveat of possible residual confounding. Compromised vaccine efficacy against the highly fit and immune-evasive B.1.617.2 Delta variant warrants continued infection control measures in the post-vaccination era