High-resolution paleoenvironmental record of Late Holocene storm activity in coastal lagoons

沿海泻湖全新世晚期风暴活动的高分辨率古环境记录

• 批准号: RGPIN-2014-05829
• 负责人: Boyce, Joseph
• 金额: $ 2.19万
• 依托单位: McMaster University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=646091
• 关键词: resolution; paleoenvironmental; record; Late; Holocene

Hurricanes and intense "post-tropical" cyclones are a major cause of severe weather in eastern Canada. Climate models predict that there will be an increase in the frequency of destructive hurricanes in the future due to climate warming. Some models suggest possible linkages with human-induced climate warming and the production of greenhouse gases. However, the available record of past storm events in North America (< 150 years) is too short to evaluate long-term trends. * *The NSERC-funded research will employ measurements of the geochemical and magnetic properties of sediments in lakes and coastal lagoons to better understand the frequency of large storm events over the last 5000 years. During large storm events, storm waves overtop sandy beach barriers depositing distinctive "overwash" sand sheets on the lake floor. Storm sediment layers are also deposited in lakes by the flood discharge of rivers. Storm overwash and flood deposits can be identified in sediment cores extracted from the lake bed and by dating of the storm event layers, the past frequency of storm events can be determined. Identification of storm layers can be difficult, however, based on the visible characteristics of the sediments alone. **In order to obtain more detailed and reliable records of past storm frequency, Boyce and research team (1 Ph.D., 2 M.Sc., 5 B.Sc. students) will investigate the geochemical and magnetic properties of storm sediment layers in coastal lagoons. By determining the abundance of distinctive elements and magnetic minerals carried by storm events, the researchers will be able geochemically "finger-print" the storm deposits. In order to obtain a detailed record of storm events, researchers will employ the new ITRAX core scanning facility at McMaster. The ITRAX core scanner uses an X-ray beam to measure very precisely the abundance of a wide range of elements in core samples. The scanner also records changes in the magnetization of the core and produces a high-resolution colour image that can be used to identify changes in sediment texture and colour. Using the combined properties, it is possible to detect very thin storm event layers (less than 2/10 of a millimetre), yielding a very detailed record of past storm events. Using this new technique, the researchers will develop a detailed history of past storm events in Lake Ontario and on the Atlantic coast of Canada (Nova Scotia, Newfoundland). **The detailed long-term record of storm events produced with the ITRAX facility will allow McMaster researchers to assess whether the frequency of storms has been different in the past, and whether the variability in storminess is linked to other climate variables, such as past changes in temperature and precipitation. These data are critical for evaluating future changes in storm frequency predicted by climate models and will assist in the development of appropriate emergency planning for heavily populated areas of eastern Canada that are at risk from severe weather.

加拿大东部的飓风和强烈的“热带”气旋是恶劣天气的主要原因。气候模型预测，由于气候变暖，未来破坏性飓风的频率将会增加。一些模型表明，可能与人类引起的气候变暖和温室气体的产生联系。但是，北美过去风暴事件的可用记录（<150年）太短了，无法评估长期趋势。 * * NSERC资助的研究将对湖泊和沿海泻湖沉积物的地球化学和磁性特性进行测量，以更好地了解过去5000年中大型风暴事件的频率。在大型暴风雨事件中，风暴波浪超过沙滩屏障，在湖地板上沉积了独特的“吹嘘”沙子。 河流的洪水排放也沉积在湖泊中。可以在从湖床中提取的沉积物核心并通过风暴事件层的约会来确定风暴过量和洪水沉积物，可以确定风暴事件的过去频率。但是，基于仅沉积物的可见特征，可能很难识别风暴层。 **为了获得过去风暴频率的更详细和可靠的记录，Boyce和研究团队（1博士学位，2 M.Sc.，5 B.Sc学生）将研究沿海泻湖中风暴沉积物层的地球化学和磁性特性。通过确定风暴事件带来的独特元素和磁性矿物质的丰富度，研究人员将能够在地球化学上“手指印刷”风暴沉积物。 为了获得风暴事件的详细记录，研究人员将在McMaster使用新的ITRAX核心扫描设施。 ITRAX核心扫描仪使用X射线梁来非常精确地测量核心样品中各种元素的丰富度。扫描仪还记录了核心磁化的变化，并产生了高分辨率的颜色图像，可用于识别沉积物纹理和颜色的变化。使用合并的属性，可以检测到非常薄的风暴事件层（小于2/10毫米），从而产生过去风暴事件的非常详细的记录。利用这项新技术，研究人员将开发安大略湖和加拿大大西洋海岸（纽芬兰新斯科舍省）过去风暴事件的详细历史。 ** ITRAX设施产生的风暴事件的详细长期记录将使McMaster研究人员能够评估过去风暴的频率是否有所不同，以及风暴性的可变性是否与其他气候变量有关，例如过去温度和降水的变化。这些数据对于评估气候模型预测的未来风暴频率变化至关重要，并将为加拿大东部地区人口稠密地区的适当紧急计划制定适当的紧急计划，这些地区面临恶劣天气的风险。