Contribution of deformation to sea-ice mass balance: a case study from an N-ICE2015 storm

The fastest and most efficient process of gaining sea ice volume is through the mechanical redistribution of mass as a consequence of deformation events. During the ice growth season divergent motion produces leads where new ice grows thermodynamically, while convergent motion fractures the ice and either piles the resultant ice blocks into ridges or rafts one floe under the other. Here we present an exceptionally detailed airborne dataset from a 9km2 area of first and second year ice in the Transpolar Drift north of Svalbard that allowed us to estimate the redistribution of mass from an observed deformation event. To achieve this level of detail we analyzed changes in sea ice freeboard acquired from two airborne laser scanner surveys just before and right after a deformation event brought on by a passing low pressure system. A linear regression model based on divergence during this storm can explain 64% of freeboard variability. Over the survey region we estimated that about 1.3% of level sea ice volume was pressed together into deformed ice and the new ice formed in leads in a week after the deformation event would increase the sea ice volume by 0.5%. As the region is impacted by about 15 storms each winter a simple linear extrapolation would result in about 7% volume increase and 20% deformed ice fraction at the end of the seaso

Thin Sea Ice, Thick Snow, and Widespread Negative Freeboard Observed During N-ICE2015 North of Svalbard

In recent years, sea-ice conditions in the Arctic Ocean changed substantially toward a younger and thinner sea-ice cover. To capture the scope of these changes and identify the differences between individual regions, in situ observations from expeditions are a valuable data source. We present a continuous time series of in situ measurements from the N-ICE2015 expedition from January to June 2015 in the Arctic Basin north of Svalbard, comprising snow buoy and ice mass balance buoy data and local and regional data gained from electromagnetic induction (EM) surveys and snow probe measurements from four distinct drifts. The observed mean snow depth of 0.53 m for April to early June is 73% above the average value of 0.30 m from historical and recent observations in this region, covering the years 1955–2017. The modal total ice and snow thicknesses, of 1.6 and 1.7 m measured with ground-based EM and airborne EM measurements in April, May, and June 2015, respectively, lie below the values ranging from 1.8 to 2.7 m, reported in historical observations from the same region and time of year. The thick snow cover slows thermodynamic growth of the underlying sea ice. In combination with a thin sea-ice cover this leads to an imbalance between snow and ice thickness, which causes widespread negative freeboard with subsequent flooding and a potential for snow-ice formation. With certainty, 29% of randomly located drill holes on level ice had negative freeboard

Математическая оценка гемолиза канального центробежного насоса

The objective of this work is to conduct research on a mathematical model to assess hemolytic characteristics in a channel centrifugal blood pump developed by us with 2000–3400 rpm impeller speed range and 100–250 mmHg pressure drop in different parts of the pump flow path. Hemolysis index was measured at 1 to 10 L/min flow rate. The result was an estimate of the average magnitude of the shear stress (SS), taking into account the distribution in the pump, which ranged from 40 to 60 Pa. The most critical areas of the pump in terms of blood injury were evaluated. The maximum SSs were determined: 456 Pa in the impeller wheel zone and 533.3 Pa in the adjacent area of the body, with an exposure time of 0.0115 s and 0.0821 s respectively. In these zones, maximum hemolysis index values were 0.0420 and 0.0744 respectively. Based on the data obtained, these zones were optimized in terms of minimizing hemolysis.Целью работы является проведение исследований на математической модели по оценке гемолитических характеристик в разработанном нами канальном центробежном насосе в диапазоне скоростей рабочего колеса 2000–3400 об/мин и перепадом давления 100–250 мм рт. cт. в разных отделах проточного тракта насоса. Расчетный индекс гемолиза проведен при скоростях потока от 1 до 10 л/мин. Результатом работы явилась оценка среднего значения касательного напряжения (КН) с учетом распределения в насосе, которое составило от 40 до 60 Па. Были проведены оценки наиболее критичных с точки зрения травмы крови зон насоса. В результате расчетов определены максимальные КН в зоне РК 456 Па и прилежащей зоне корпуса 533,3 Па, при соответствующем времени экспозиции 0,0115 и 0,0821 с. В этих зонах наблюдаются максимальные значения ИГ 0,0420 и 0,0744. На основании полученных данных была проведена оптимизация данных зон с точки зрения минимизации гемолиза