Photon echo in the ensemble of semiconductor quantum dots spread on a glass substrate

Simple procedure to prepare samples containing semiconductor quantum dots was developed. Test photon echo measurements in the ensemble of quantum dots spread on a glass substrate were performed to study optical dephasing processes

Original Russian Text ©

Methane hydrates are widely spread in the perma frost regions and bottom sediment rocks of the ocean. The total reserves of carbon in the form of hydrates are estimated at 10 4 Gt C [1], which is one order of magni tude greater than its content in the atmosphere The temperature increase during global warming facilitates destabilization and dissociation of aggre gates of subaquatic hydrates and emissions of poten tially large amounts of methane into the atmosphere. Such emissions can result in significant global and regional climatic consequences with accelerated dis sociation of hydrates. Dissociation of methane hydrates could have been the cause of the rapid cli matic changes in the past The stability of hydrates in the bottom sediments of inland reservoirs depends on temperature and pres sure. Hydrostatic pressure at the bottom in the loca tions of methane hydrates exceeds the pressure needed for the stability of hydrates at the temperature of the bottom water. Hydrates are usually not formed over the bottom owing to the insufficient concentration of methane. As the depth below the bottom increases, hydrostatic pressure and temperature increase linearly (in the equilibrium conditions), while the pressure needed for the stability of methane hydrates exponen tially depends on temperature. Owing to this fact, the lower boundary of the stability zone exists. An increase in the bottom water temperature leads to a change in the temperature profile in the bottom sediments and to the corresponding displacement of the stability zone boundaries. The bottom water temperature in Lake Baikal is currently approximately 3.5°C at depths exceeding 200 m We carried out numerical experiments using the method for calculation of methane reserves in the bot tom deposits of gas hydrates similarly to [10] to esti mate the time intervals needed for the dissociation of hydrates. We specified the temperature gradient that corresponds to the equilibrium state at the geothermal flux equal to 0.09 W/m 2 characteristic of the deep water part of Lake Baikal as the initial condition for the model of bottom sediment

Original Russian Text ©

Methane hydrates are widely spread in the perma frost regions and bottom sediment rocks of the ocean. The total reserves of carbon in the form of hydrates are estimated at 10 4 Gt C [1], which is one order of magni tude greater than its content in the atmosphere The temperature increase during global warming facilitates destabilization and dissociation of aggre gates of subaquatic hydrates and emissions of poten tially large amounts of methane into the atmosphere. Such emissions can result in significant global and regional climatic consequences with accelerated dis sociation of hydrates. Dissociation of methane hydrates could have been the cause of the rapid cli matic changes in the past The stability of hydrates in the bottom sediments of inland reservoirs depends on temperature and pres sure. Hydrostatic pressure at the bottom in the loca tions of methane hydrates exceeds the pressure needed for the stability of hydrates at the temperature of the bottom water. Hydrates are usually not formed over the bottom owing to the insufficient concentration of methane. As the depth below the bottom increases, hydrostatic pressure and temperature increase linearly (in the equilibrium conditions), while the pressure needed for the stability of methane hydrates exponen tially depends on temperature. Owing to this fact, the lower boundary of the stability zone exists. An increase in the bottom water temperature leads to a change in the temperature profile in the bottom sediments and to the corresponding displacement of the stability zone boundaries. The bottom water temperature in Lake Baikal is currently approximately 3.5°C at depths exceeding 200 m We carried out numerical experiments using the method for calculation of methane reserves in the bot tom deposits of gas hydrates similarly to [10] to esti mate the time intervals needed for the dissociation of hydrates. We specified the temperature gradient that corresponds to the equilibrium state at the geothermal flux equal to 0.09 W/m 2 characteristic of the deep water part of Lake Baikal as the initial condition for the model of bottom sediment

Northern Eurasia Future Initiative (NEFI): facing the challenges and pathways of global change in the 21st century

During the past several decades, the Earth system has changed significantly, especially across Northern Eurasia. Changes in the socio-economic conditions of the larger countries in the region have also resulted in a variety of regional environmental changes that can have global consequences. The Northern Eurasia Future Initiative (NEFI) has been designed as an essential continuation of the Northern Eurasia Earth Science Partnership Initiative (NEESPI), which was launched in 2004. NEESPI sought to elucidate all aspects of ongoing environmental change, to inform societies and, thus, to better prepare societies for future developments. A key principle of NEFI is that these developments must now be secured through science-based strategies co-designed with regional decision makers to lead their societies to prosperity in the face of environmental and institutional challenges. NEESPI scientific research, data, and models have created a solid knowledge base to support the NEFI program. This paper presents the NEFI research vision consensus based on that knowledge. It provides the reader with samples of recent accomplishments in regional studies and formulates new NEFI science questions. To address these questions, nine research foci are identified and their selections are briefly justified. These foci include: warming of the Arctic; changing frequency, pattern, and intensity of extreme and inclement environmental conditions; retreat of the cryosphere; changes in terrestrial water cycles; changes in the biosphere; pressures on land-use; changes in infrastructure; societal actions in response to environmental change; and quantification of Northern Eurasia's role in the global Earth system. Powerful feedbacks between the Earth and human systems in Northern Eurasia (e.g., mega-fires, droughts, depletion of the cryosphere essential for water supply, retreat of sea ice) result from past and current human activities (e.g., large scale water withdrawals, land use and governance change) and potentially restrict or provide new opportunities for future human activities. Therefore, we propose that Integrated Assessment Models are needed as the final stage of global change assessment. The overarching goal of this NEFI modeling effort will enable evaluation of economic decisions in response to changing environmental conditions and justification of mitigation and adaptation efforts

Impact of climate changes over the extratropical land on permafrost dynamics under RCP scenarios in the 21st century as simulated by the IAP RAS climate model

Estimates of possible climate changes and cryolithozone dynamics in the 21st century over the Northern Hemisphere land are obtained using the IAP RAS global climate model under the RCP scenarios. Annual mean warming over the northern extratropical land during the 21st century amounts to 1.2-5.3°C depending on the scenario. The area of the snow cover in February amounting currently to 46 million km2 decreases to 33-42 million km2 in the late 21st century. According to model estimates, the near-surface permafrost in the late 21st century persists in northern regions of West Siberia, in Transbaikalia, and Tibet even under the most aggressive RCP 8.5 scenario; under more moderate scenarios (RCP 6.0, RCP 4.5, and RCP 2.6), it remains in East Siberia and in some high-latitude regions of North America. The total near-surface permafrost area in the Northern Hemisphere in the current century decreases by 5.3-12.8 million km2 depending on the scenario. The soil subsidence due to permafrost thawing in Central Siberia, Cisbaikalia, and North America can reach 0.5-0.8 m by the late 21st century. © 2013 Allerton Press, Inc

Impact of climate changes over the extratropical land on permafrost dynamics under RCP scenarios in the 21st century as simulated by the IAP RAS climate model

Estimates of possible climate changes and cryolithozone dynamics in the 21st century over the Northern Hemisphere land are obtained using the IAP RAS global climate model under the RCP scenarios. Annual mean warming over the northern extratropical land during the 21st century amounts to 1.2-5.3°C depending on the scenario. The area of the snow cover in February amounting currently to 46 million km2 decreases to 33-42 million km2 in the late 21st century. According to model estimates, the near-surface permafrost in the late 21st century persists in northern regions of West Siberia, in Transbaikalia, and Tibet even under the most aggressive RCP 8.5 scenario; under more moderate scenarios (RCP 6.0, RCP 4.5, and RCP 2.6), it remains in East Siberia and in some high-latitude regions of North America. The total near-surface permafrost area in the Northern Hemisphere in the current century decreases by 5.3-12.8 million km2 depending on the scenario. The soil subsidence due to permafrost thawing in Central Siberia, Cisbaikalia, and North America can reach 0.5-0.8 m by the late 21st century. © 2013 Allerton Press, Inc

Impact of climate changes over the extratropical land on permafrost dynamics under RCP scenarios in the 21st century as simulated by the IAP RAS climate model

Estimates of possible climate changes and cryolithozone dynamics in the 21st century over the Northern Hemisphere land are obtained using the IAP RAS global climate model under the RCP scenarios. Annual mean warming over the northern extratropical land during the 21st century amounts to 1.2-5.3°C depending on the scenario. The area of the snow cover in February amounting currently to 46 million km2 decreases to 33-42 million km2 in the late 21st century. According to model estimates, the near-surface permafrost in the late 21st century persists in northern regions of West Siberia, in Transbaikalia, and Tibet even under the most aggressive RCP 8.5 scenario; under more moderate scenarios (RCP 6.0, RCP 4.5, and RCP 2.6), it remains in East Siberia and in some high-latitude regions of North America. The total near-surface permafrost area in the Northern Hemisphere in the current century decreases by 5.3-12.8 million km2 depending on the scenario. The soil subsidence due to permafrost thawing in Central Siberia, Cisbaikalia, and North America can reach 0.5-0.8 m by the late 21st century. © 2013 Allerton Press, Inc

Photon echo in the ensemble of semiconductor quantum dots spread on a glass substrate

Simple procedure to prepare samples containing semiconductor quantum dots was developed. Test photon echo measurements in the ensemble of quantum dots spread on a glass substrate were performed to study optical dephasing processes