Numerical modeling of adiabatic heat generation during rock fracture under dynamic loading     

Timo Saksala 《国际地质力学数值与分析法杂志》2019,43(9):1770-1783

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The Seasonal Characteristics of Equatorial Plasma Bubbles in Conjugate Hemispheres During 2015     

Erdinç Timoçin  Temuçin  Hüseyin  İnyurt  Samed 《Geomagnetism and Aeronomy》2022,62(3):309-323

Geomagnetism and Aeronomy - In this paper, using the Total Electron Content (TEC) data obtained from GUAM (13.58° N, 144.86° E) and PNGM (2.04° S, 147.36° E) Global Positioning...  相似文献   

Deglaciation chronology of the Scandinavian Ice Sheet from the Lake Onega Basin to the Salpausselkä End Moraines     

Matti Saarnisto  Timo Saarinen 《Global and Planetary Change》2001,31(1-4)

Several long sediment cores (max. 12 m) from various parts (up to 150 km apart) of Lake Onega, Russian Karelia, have been studied for lithology, varve chronology and palaeomagnetism. The two longest varve records from the central basin contain 1300 varves. These indicate the length of the deglaciation period from these localities to the north of Lake Onega, where the drainage of glacial meltwaters was directed towards the White Sea and the deposition of varves in the Onega basin terminated. An estimate of the duration of deglaciation of the whole Onega basin is 1500 years. Natural remanent magnetization (NRM) is strong and stable in these sediments and accurately records changes in the Earth's magnetic field. A distinct change in the magnetic field, when the declination shifted from east to west by at least 60° in 350 varve years, is clearly identifiable in all cores. This palaeomagnetic feature was used for core to core correlation together with other variations in magnetic parameters and widely distributed lithological marker horizons. On the basis of the correlations between the cores and calibration of AMS radiocarbon dates from varves obtained from the northern archipelago of Lake Onega, the age of the westerly declination peak is dated to 13 090 cal. BP and accordingly the deglaciation of the Onega basin took place between 14 250 and 12 750±100 cal. BP. The westerly declination peak was also recognized earlier by Bakhmutov and Zagniy in the Helylä varved clay sequence near Sortavala on the northern shore of Lake Ladoga. Helylä is situated outside the Salpausselkä end moraines and the accumulation of varved clays continued there 1500 years after the declination peak, up until the drainage of the Baltic Ice Lake, which more or less coincides with the ice margin retreat from Salpausselkä II end moraine and the termination of the Younger Dryas event. The date thus arrived at for this event is 11 590±100 cal. BP, close to the recent results from Greenland ice cores and from varved lake sediments and tree rings from Central Europe. It is further suggested that the formation of the major Younger Dryas end moraines, the Finnish Salpausselkä I and Salpausselkä II and their correlatives in Russian Karelia, took place between 12 250 and 11 590 calendar years ago, clearly earlier than earlier estimated through correlation with the Swedish varve chronology.  相似文献   

Foreword     

Matti Lepp?ranta  Timo Vihma  Huiding Wu 《极地研究(英文版)》2014,(4)

正Rapid changes of Arctic sea ice cover have been in the focus of the international climate research community in recent years.Quite a few of nations have completed a large number of related surveys and research projects in the Arctic Ocean.Up to now,China has performed six research cruises to the Arctic Ocean resulting in a significant volume of research output.Improved knowledge on the atmospheree-sea ice-ocean interactions in the Arctic is a  相似文献   

Modeling Fine‐Scale Geological Heterogeneity—Examples of Sand Lenses in Tills     

Timo Christian Kessler  Alessandro Comunian  Fabio Oriani  Philippe Renard  Bertel Nilsson  Knud Erik Klint  Poul Løgstrup Bjerg 《Ground water》2013,51(5):692-705

Sand lenses at various spatial scales are recognized to add heterogeneity to glacial sediments. They have high hydraulic conductivities relative to the surrounding till matrix and may affect the advective transport of water and contaminants in clayey till settings. Sand lenses were investigated on till outcrops producing binary images of geological cross‐sections capturing the size, shape and distribution of individual features. Sand lenses occur as elongated, anisotropic geobodies that vary in size and extent. Besides, sand lenses show strong non‐stationary patterns on section images that hamper subsequent simulation. Transition probability (TP) and multiple‐point statistics (MPS) were employed to simulate sand lens heterogeneity. We used one cross‐section to parameterize the spatial correlation and a second, parallel section as a reference: it allowed testing the quality of the simulations as a function of the amount of conditioning data under realistic conditions. The performance of the simulations was evaluated on the faithful reproduction of the specific geological structure caused by sand lenses. Multiple‐point statistics offer a better reproduction of sand lens geometry. However, two‐dimensional training images acquired by outcrop mapping are of limited use to generate three‐dimensional realizations with MPS. One can use a technique that consists in splitting the 3D domain into a set of slices in various directions that are sequentially simulated and reassembled into a 3D block. The identification of flow paths through a network of elongated sand lenses and the impact on the equivalent permeability in tills are essential to perform solute transport modeling in the low‐permeability sediments.  相似文献   

Resistance to the deinstitutionalization of a region: Borders,identity and activism in a municipality merger     

Kaj Zimmerbauer  Timo Suutari  Antti Saartenoja 《Geoforum》2012,43(6):1065-1075

Regions are contested processes in which various layers of borders become articulated, deconstructed and reconstructed by both activists and advocates. While many scholars currently tend to highlight the relational character of spaces, this study – acknowledging that seeing regions as relational or territorial is a highly contextual matter – emphasizes the territorial approach by stressing the multiple layers of borders and how they help to constitute and nurture regional identity. Focusing on deinstitutionalization of a region, it is argued here that regional restructuring can trigger activism, as proved by the activist movement at issue in the case study. This case study of a merger between two municipalities in Finland illustrates that when threatened with integration, (old) regions seem to be of especial importance as bordered territories of identification.  相似文献   

Carbon Budget and Molecular Structure of Natural Organic Matter in Bank Infiltrated Groundwater     

Maija Jylhä-Ollila  Hanne Laine-Kaulio  Jos Schilder  Paula Niinikoski-Fuβwinkel  Timo Kekäläinen  Janne Jänis  Harri Koivusalo 《Ground water》2021,59(5):644-657

Managed aquifer recharge (MAR) provides means to remove natural organic matter (NOM) from surface waters. Recent studies have explored the degree of NOM removal in groundwater. In this study, we further elaborate the NOM removal at a lakeside natural bank infiltration site that functions as a surrogate for MAR. Our objective was to quantify the carbon budget in the aquifer based on concentration measurements of dissolved (in)organic carbon, and the molecular changes in NOM using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). According to the carbon budget, only 25% of the dissolved carbon entering the aquifer was organic, and it predominantly originated from lake water. Of the inorganic majority, on average 40% was produced in the vadose zone above the groundwater table, 31% in the lake bank, 22% in the aquifer as a result of degrading organic matter of lake water, and 7% in the lake. Seasonal concentration variations suggested that the lake bank was the main carbon source in the summer, increasing the carbon concentration of infiltrating lake water, that is, 3.0 mg/L to 7.9 mg/L. FT-ICR MS results showed 4960 to 5330 individual compounds in lake and groundwater. NOM removal in the aquifer was selective: the relative abundance of oxygen-containing species decreased from 75 to 31%, while the relative abundance of sulfur-containing species increased from 15 to 57%. The average molecular weights of both species remained unchanged. The study highlighted the role of lake bank processes and sulfur-containing species in groundwater quality.  相似文献   

‘Observations and Modelling of Cold-air Advection over Arctic Sea Ice’     

Timo?VihmaEmail author  Christof?Lüpkes  J?rg?Hartmann  Hannu?Savij?rvi 《Boundary-Layer Meteorology》2005,117(2):275-300

Aircraft observations of the atmospheric boundary layer (ABL) over Arctic sea ice were made during non-stationary conditions of cold-air advection with a cloud edge retreating through the study region. The sea-ice concentration, roughness, and ABL stratification varied in space. In the ABL heat budget, 80% of the Eulerian change in time was explained by cold-air advection and 20% by diabatic heating. With the cloud cover and inflow potential temperature profile prescribed as a function of time, the air temperature and near-surface fluxes of heat and momentum were well simulated by the applied two-dimensional mesoscale model. Model sensitivity tests demonstrated that several factors can be active in generating unstable stratification in the ABL over the Arctic sea ice in March. In this case, the upward sensible heat flux resulted from the combined effect of clouds, leads, and cold-air advection. These three factors interacted non-linearly with each other. From the point of view of ABL temperatures, the lead effect was far less important than the cloud effect, which influenced the temperature profiles via cloud-top radiative cooling and radiative heating of the snow surface. The steady-state simulations demonstrated that under overcast skies the evolution towards a deep, well-mixed ABL may take place through the merging of two mixed layers one related to mostly shear-driven surface mixing and the other to buoyancy-driven top-down mixing due to cloud-top radiative cooling.  相似文献   

Environmental literacy in interpreting endangered sustainability: Case studies from Thailand and the Sudan     

Minna Hares  Anu Eskonheimo  Timo Myllyntaus 《Geoforum》2006,37(1):128-144

This paper examines how people explain reasons and impacts of environmental change in the low-rain savanna of the central Sudan and mountainous forest lands of northern Thailand. The explanations are analyzed by using the concept of environmental literacy, which refers to the people’s ability to grasp the environment and its interactions. The paper aims to study people’s conceptions of the environment, which compose one factor in directing their behavior. For the study, rural inhabitants in the State of North Kordofan, the Sudan, and the Chiang Mai Province in Thailand were interviewed.It was noted that an individual’s capability to understand the environment is alone insufficient to address environmental problems because the efficient alleviation of the problems requires collective actions at all levels, and because of factors beyond an individual’s control. However, the results supported the assumption that the local people have knowledge of their environment that may help in developing sustainable environmental management practices. The main advantages of using the environmental literacy concept are argued to be its dynamic and synthetic essence, its link to sustainable behavior, and wide applicability in various contexts within heterogeneous communities.  相似文献   

Increased Carbon Sink in Temperate and Boreal Forests   总被引：6，自引：0，他引：6  

Jari Liski  Alexander V. Korotkov  Christopher F. L. Prins  Timo Karjalainen  David G. Victor  Pekka E. Kauppi 《Climatic change》2003,61(1-2):89-99

An intense search is under way to identify the `missing sink' in the world carbon budget of perhaps 2 Pg year^–1 (petagrams, or billiontonnes) of carbon, but its location and mechanism have proved elusive. Here we use a new forest inventory data set to estimate the carbon sink and the carbon pool of woody biomass in 55 countries that account for nearly all temperate or boreal forests and approximately half the world's total forest area. In each country there was a net accumulation of biomass; together, the carbon sink of woody biomass was 0.88 Pg year^–1 during the 1990swith estimated uncertainty from 0.71 to 1.1 Pg year^–1. Thisestimate, already about half of the missing sink, would probably be even larger if carbon accumulation in soil and detritus were also accounted for, but we are unable to quantify that additional sink. The sink is twice that estimated for the woody biomass of these forests a decade ago due to higher estimates for tree growth throughout the region and decreased timber harvests in Russia. In contrast, the new data indicate a carbon pool that is smaller than earlier estimates because of improved data for Russia and Australia.  相似文献