Mechanics and dynamics of mineral dust production within cold climates

点击翻译按钮获取中文摘要

Atmospheric aerosols are a complex mixture of inorganic and organic components and can range in size from a few nanometers to several 10s of micrometers. An important fraction of the total global aerosol budget is mineral dust aerosols (MDA), which augment the atmospheric radiation budget by directly reflecting or absorbing solar radiation and indirectly, by acting as cloud condensation or ice nuclei, altering cloud properties such as albedo, lifetime, and the quantity of precipitation. Once deposited, MDA can behave like a black body, disproportionately enhancing the melting of snow surfaces, as well as providing essential nutrients to ecosystems. No existing estimates of the Canadian total annual MDA emissions are currently available despite an estimate of 80-100 Tg or 5-8% per year of the global MDA burden from high latitude fugitive sources. The current and historical source identification difficulties in these northern latitudes and within Canada specifically are due to highly seasonal emissions, low level and consistent cloud cover, accessibility, low density of existing monitoring or infrastructure, and minimal attempts to involve local communities within research programs. Many polar landscapes exhibit sporadic or extensive discontinuous permafrost and are subject to limited annual precipitation, limiting the transport connectivity between regions and therefore the functional nutrient transfer through the landscape, enhancing the importance of atmospheric deposition of soluble nutrients in polar landscapes. In addition, mountainous regions are prone to meteorological conditions that produce daily thermal drainage (e.g., katabatic) winds that can erode and transport MDA regularly when the soil surface is free of snow, thawed, and has limited surface water. As average temperatures rise disproportionally in the North resulting in decreasing snowfall cover duration, earlier thawing, and increased river flow variability, more areas will be prone to wind erosion from increased areas of bare unfrozen soil for longer periods. In many regions where wind erosion is a significant hazard, vegetation can play a vital role in reducing the wind speeds at the surface and therefore reducing the frequency of MDA. Within the northern context, the ongoing increase in shrub species over native grasses promotes wind erosion by exposing more of the soil surface, as seen in many regions where wildfire disturbances promote the replacement of native grasses. This research program will aim to identify the mechanisms, extent, and frequency of MDA emissions within the Canadian North and explore the cumulative impacts of these emissions within the Canadian and global context historically, currently, and under future climate scenarios. The proposed research program will continue several research projects funded by other agencies on exploring some of these aspects with an approach that is inclusive, indigenous community-supported, and partnership-assisted.