Climate Change Data Portal
| Climate and environmental reconstructions over the last millennium from Mt. Elbrus ice cores in the Northern Caucasus and southern part of European Russia | |
| 项目编号 | 20-17-18008 |
| Mikhalenko Vladimir | |
| 项目主持机构 | Institute of Geography of the Russian Academy of Sciences, |
| 开始日期 | 2020 |
| 结束日期 | 2021 |
| 英文摘要 | The question of the presence of ancient ice in the Caucasus is still open. According to the calculations of the mass turnover time of Caucasian glaciers based on the accumulation rate, ice thickness and temperature, it was estimated as several hundred years. Direct dating of bottom layers in the ice core from the Western plateau of Elbrus showed that the ice age can reach 2000 years. Other potential places where ancient ice may be encountered are the upper part of the Bezengi wall and the Eastern peak of Elbrus. Our 2017 studies showed that the accumulation at the Eastern crater is about 500 mm w.e., i.e. 3 times less than on the Western plateau, and the temperature of the snow-firn reaches -19 °C. This suggests that relatively ancient ice may be present in the bottom of the glacier. At the same time, in the analysis of a shallow firn core, pronounced seasonal variations in the oxygen isotopic composition (δ18O) were found that persist in the thickness despite the deflation of a part of the annual layer in the winter. We suggest that the ice in the crater of the Eastern peak of Elbrus may be more ancient in comparison with other glaciers of the Caucasus. Therefore, this glacier will be the main object of research for the next two years. A fundamentally new task to be solved in the frame of the project will be to establish a relationship between the isotopic composition of oxygen and hydrogen in the precipitation depositing on the Azau meadow with the distribution of δ18O and δ2H in seasonal snow pits on the slopes of the Mt. Elbrus on different altitudes. As for the Western plateau of the Mt. Elbrus, we identified a great variability of the snow accumulation rate. It is associated with a strong wind drift, as well as a frequent change in the air masses bringing moisture to the area. We are supposed to trace changes of the general pattern in seasonal isotopic records formation at the foot and on the slopes (peaks) of the Mt. Elbrus. All the precipitation events will be linked to the moisture origin area and its trajectory toward Mt. Elbrus using the HYSPLIT NOAA model and the baric field maps. A foreseen perspective of this project could be fine and non-trivial study of the stable water isotopic composition link to the precipitations of different origin: convective, front and orographic. It will give us a possibility to trace the predominant precipitation type differentiated by seasons and to establish influence of seasonality in precipitation types to the isotopic signal in the ice core samples. In order to interpret the climatic signal in the ice core isotopic record we will imply the potential energy of convection, which was successfully used in the precipitation reconstruction. The implication of this parameter will allow distinguishing more clearly between the precipitation of cold and warm seasons and using the meteorological observations on the nearest stations, such as surface air temperature and precipitation amount, more trustfully. We will perform a spore-pollen analysis and determination of non-pollen palynomorphs of a 24-meter firn core to separate annual horizons in cores for summer and winter seasons and compare with the current plant dusting regime in the region. Trace elements analysis of Elbrus ice cores will reveal short-term regional changes in the atmospheric composition over the past centuries. Special attention will be paid to the analysis of the influence of the volcanic activity of Elbrus on the chemical composition of ice cores obtained earlier, as well as new samples that are planned to be obtained in the region of the Eastern Peak. For a quantitative assessment of the effect of microparticle deposition on the melting of snow and ice, a detailed knowledge of the size distribution of dust particles, dust flux and concentrations is required. It is also necessary to better understand the spatial variability of dust flux on a regional and global scale. For the next two years, the project aims to analyze the content of microparticles in Elbrus ice cores, determine the particle size and mass, and also calculate the dust flux. In this project, methane content in ice cores will be analyzed. We will combine the new methane concentration data from the Elbrus ice cores with published records from low latitudes. New data on the quantitative contribution of methane sources will allow to verify methane flux models. The regional concentration of methane in the atmosphere during the Late Holocene will be reconstructed. By means of the wavelet transform of methane concentrations series, the presence of cyclic fluctuations (possibly decade or century) and their modification with time will be analyzed, and assumptions about the causes of the observed phenomenon will be advanced. Based on the Monin-Obukhov methods and eddy covariance, snow drift will be calculated. To achieve this goal, additional measurements of turbulent momentum, heat and moisture flows in the accumulation zone will be carried out. A simple algorithm for calculating the orographic precipitation additive and its verification according to ice core data will be created. The orographic component of the condensation rate will be calculated based on the saturation pressure of water vapor changes with altitude considering adiabatic air cooling. The contribution of the orographic factor to the process of condensation of water vapor and the potential water content of clouds will be estimated. The condensation rate will be calculated from air temperature, humidity and wind speed on isobaric surfaces ERA5 reanalysis data. The obtained values of the orographic additive will be compared with the nearest meteorological station data and ice cores. An analysis of the cyclone trajectories bringing precipitation to the Central Caucasus will be made on the base of ERA5 reanalysis data. “lifetime” of the atmospheric moisture will be calculated for the Elbrus and Central Caucasus area using mesoscale numerical atmospheric WRF-ARW model. In the proposed project, we will solve two problems that differ significantly in their statement: 1) creating a flow model for an ice-firn mass with its subsequent dating (for two Elbrus glaciers); 2) reconstruction of temperature changes on the surface of the glacier based on the results of borehole temperature measurements. The solution of the first problem will be based on the application of a three-dimensional Stokes flow model for a compressible viscous heat-conducting fluid (ice). In this case, the rheological law for porous ice will be used. The dating of the ice-firn thickness will be performed by solving the boundary value problem for the transport equation in the three-dimensional domain occupied by the glacier. The second task – reconstruction of past temperature changes - is an ill-posed inverse problem of mathematical physics. To carry out the reconstruction, it is proposed to use the Bayesian approach and Markov Chain Monte Carlo methods in conjunction with solving the direct problem of heat conduction. In both cases, the simulation will be performed numerically. Detailed GPR survey will be completed at the wester plateau using low frequency pulsed radar VIRL-7 to clarify the previous data on the ice thickness and bedrock topography. Detailed geodetic survey will be done by differential GPS -Topcon GB 500. In order to assess the accumulation of snow and its spatial distribution we will conduct a survey using high -frequency radar (400-800 MHz ). Analysis of internal reflections on the radiograms will evaluate the dielectric constant of each layer, the velocity of electromagnetic waves propagation in layers of snow and firn will enable the determination of its density. |
| 英文关键词 | Ice cores;climatic changes;high resolution reconstructions;glacier variations;climate models;Elbrus;radio-echo sounding |
| 学科分类 | 08 - 地球科学 |
| 资助机构 | RU-RSF |
| 国家 | RU |
| 语种 | 英语 |
| 文献类型 | 项目 |
| 条目标识符 | http://gcip.llas.ac.cn/handle/2XKMVOVA/191721 |
| 推荐引用方式 GB/T 7714 | Mikhalenko Vladimir.Climate and environmental reconstructions over the last millennium from Mt. Elbrus ice cores in the Northern Caucasus and southern part of European Russia.2020. |
| 条目包含的文件 | 条目无相关文件。 | |||||
| 个性服务 |
| 推荐该条目 |
| 保存到收藏夹 |
| 导出为Endnote文件 |
| 谷歌学术 |
| 谷歌学术中相似的文章 |
| [Mikhalenko Vladimir]的文章 |
| 百度学术 |
| 百度学术中相似的文章 |
| [Mikhalenko Vladimir]的文章 |
| 必应学术 |
| 必应学术中相似的文章 |
| [Mikhalenko Vladimir]的文章 |
| 相关权益政策 |
| 暂无数据 |
| 收藏/分享 |
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。
