КОНВЕКЦИЯ ВОЗДУХА В СНЕЖНОМ ПОКРОВЕ МОРСКОГО ЛЬДА (AIR CONVECTION IN SNOW COVER OF SEA ICE)

For the first time, data on stability of stationary convective filtration within infinite horizontal layer of snow covering the flat surface of floating ice is presented in this article. An analytical solution of the linearized problem was obtained with the use of the Galerkin method, and the parametric analysis of the problem was performed. It was found that the stability criteria (Rayleigh filtration numbers) obtained with consideration for the heat exchange of snow cover with the atmosphere did not exceed the known value of 4π2 for a horizontal porous layer with impermeable isothermal boundaries. As expected, the interaction with the atmosphere has the most significant impact on the critical Rayleigh numbers, while influence of variations in snow density and ice thickness and the thickness of the underlying layer of ice are small. Based on data of ice and meteorological observations made in the winter of 2015/16 in the Western part of the Laptev Sea together with calculations of the fast ice evolution, the values and temporal variability of temperature gradients and the Rayleigh numbers in the snow cover were obtained using a thermodynamic model. It was found that both, the model and observed magnitudes, exceeded their critical values determined by solving the stability problem. The conclusion is made that the convective regime of the heat transfer does really exist in the snow cover, and thus its contribution to the thermal and mass balance of sea ice during winter period should be taken into account

Возникновение термической конвекции в мохово-снежном покрове побережья залива Грёнфьорд (Западный Шпицберген)

The significant part of the Arctic soils is covered by vegetation all year round, to which a layer of snow is added in winter. Both layers have a similar structure, consisting of a skeleton (organic and ice, respectively) and air-saturated pores, and, thus, form a unified system with high heat-insulating properties. But, with the temperature gradient within the layers, convection can arise, which significantly reduces the thermal resistance of the layers and affects the heat, mass and gas exchange of the atmospheric boundary layer with the ground. In this connection, the role of convective transport in the formation of the thermodynamic and biogeochemical regime of polar ecosystems becomes obvious. Note that the role of convection in the snow cover is discussed in literature, but similar studies for vegetation are absent. This is one of the reasons why the processes of heat and mass transfer in the moss-snow layer above the ground in high latitudes are reproduced in a very simplified way, even in the most advanced models of the Earth system. In this paper, we study the occurrence of instability in a system of two porous layers with heat-insulated boundaries for conditions that approximate the snow and vegetation cover of the Arctic tundra on the coast of the Gulf of Grenfjord (West Spitsbergen). The analytical solution of the Rayleigh-Darcy problem is obtained by means of expansion of the amplitudes of perturbations of vertical velocity and air temperature into series. The dependence of the convective instability threshold on the variations of the thermal physical properties of the vegetation and snow cover of the studied region, parameterized according to measurement data and literature sources, is estimated. It has been found that the stability threshold increases with growth of snow thickness and density. It was also shown that the non-Rayleigh instability becomes impossible when heated from above (meaning the long-wave mode), which occurs in a similar system of two layers of homogeneous immiscible liquids due to the difference in their thermal physical properties.С использованием метода малого параметра получено аналитическое решение задачи Рэлея– Дарси для двухслойного мохово-снежного покрова арктической тундры побережья Западного Шпицбергена. Оценена зависимость порога длинноволновой конвективной неустойчивости от теплофизических свойств слоёв, показаны качественные отличия рассмотренной задачи от аналогичной задачи для однородных жидкостей

Конвекция воздуха в снежном покрове морского льда

For the first time, data on stability of stationary convective filtration within infinite horizontal layer of snow covering the flat surface of floating ice is presented in this article. An analytical solution of the linearized problem was obtained with the use of the Galerkin method, and the parametric analysis of the problem was performed. It was found that the stability criteria (Rayleigh filtration numbers) obtained with consideration for the heat exchange of snow cover with the atmosphere did not exceed the known value of 4π2 for a horizontal porous layer with impermeable isothermal boundaries. As expected, the interaction with the atmosphere has the most significant impact on the critical Rayleigh numbers, while influence of variations in snow density and ice thickness and the thickness of the underlying layer of ice are small. Based on data of ice and meteorological observations made in the winter of 2015/16 in the Western part of the Laptev Sea together with calculations of the fast ice evolution, the values and temporal variability of temperature gradients and the Rayleigh numbers in the snow cover were obtained using a thermodynamic model. It was found that both, the model and observed magnitudes, exceeded their critical values determined by solving the stability problem. The conclusion is made that the convective regime of the heat transfer does really exist in the snow cover, and thus its contribution to the thermal and mass balance of sea ice during winter period should be taken into account.Построено решение задачи устойчивости воздуха в снежном покрове на морском льду. Рассмотрены различные варианты динамических и тепловых граничных условий, проведено параметрическое исследование задачи. Выполнено сравнение данных моделирования с результатами расчётов для реальных ледовых и метеорологических условий

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

Growth of landfast ice and its thermal interaction with bottom sediments in the Braganzav{\r a}gen Gulf (West Spitsbergen)

The results of ice and hydrological studies of the shallow Bay of Braganzavågen (Van Mayen Fjord Bay, West Spitsbergen Island) in March 2016 and 2018, supplemented with model calculations using a thermodynamic model, are presented. The model uses both known methods of localizing the phase transition region-the classical (frontal) for fast ice and in an extended area (two-phase zone) for bottom sediments. For real atmospheric conditions of winter 2015-2016, the new qualitative features of the process of ice formation in the adjacent layers of sea water and bottom soil are revealed. However, due to insufficient knowledge of the heat and mass transfer properties of bottom sediments, the question of quantitative estimates of the process remains open and can be clarified in special field experiments

Mirror proteorhodopsins

Abstract Proteorhodopsins (PRs), bacterial light-driven outward proton pumps comprise the first discovered and largest family of rhodopsins, they play a significant role in life on the Earth. A big remaining mystery was that up-to-date there was no described bacterial rhodopsins pumping protons at acidic pH despite the fact that bacteria live in different pH environment. Here we describe conceptually new bacterial rhodopsins which are operating as outward proton pumps at acidic pH. A comprehensive function-structure study of a representative of a new clade of proton pumping rhodopsins which we name “mirror proteorhodopsins”, from Sphingomonas paucimobilis (SpaR) shows cavity/gate architecture of the proton translocation pathway rather resembling channelrhodopsins than the known rhodopsin proton pumps. Another unique property of mirror proteorhodopsins is that proton pumping is inhibited by a millimolar concentration of zinc. We also show that mirror proteorhodopsins are extensively represented in opportunistic multidrug resistant human pathogens, plant growth-promoting and zinc solubilizing bacteria. They may be of optogenetic interest