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: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=611870
• 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.

飓风和强烈的“后热带”气旋是加拿大东部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存在联系。然而，北美过去风暴事件（< 150 年）的可用记录太短，无法评估长期趋势。 NSERC 资助的研究将采用对湖泊和沿海泻湖沉积物的地球化学和磁性的测量，以更好地了解过去 5000 年大型风暴事件的频率。在大型风暴事件期间，风暴波会冲过沙滩屏障，在湖底沉积独特的“过度冲刷”沙层。河流的泄洪也会使风暴沉积物沉积在湖泊中。可以在从湖床提取的沉积物核心中识别风暴过度冲刷和洪水沉积物，并且通过对风暴事件层进行测年，可以确定风暴事件过去的频率。然而，仅根据沉积物的可见特征来识别风暴层可能很困难。 为了获得过去风暴频率的更详细和可靠的记录，博伊斯和研究团队（1名博士生、2名硕士生、5名理学士学位生）将研究沿海泻湖风暴沉积层的地球化学和磁性特性。通过确定风暴事件携带的独特元素和磁性矿物的丰度，研究人员将能够对风暴沉积物进行地球化学“指纹识别”。为了获得风暴事件的详细记录，研究人员将在麦克马斯特使用新的 ITRAX 核心扫描设施。 ITRAX 岩心扫描仪使用 X 射线束非常精确地测量岩心样品中各种元素的丰度。扫描仪还记录岩心磁化强度的变化，并生成高分辨率彩色图像，可用于识别沉积物纹理和颜色的变化。利用组合特性，可以检测非常薄的风暴事件层（小于 2/10 毫米），从而生成过去风暴事件的非常详细的记录。利用这项新技术，研究人员将详细记录安大略湖和加拿大大西洋沿岸（新斯科舍省、纽芬兰省）过去风暴事件的历史。 ITRAX 设施产生的风暴事件的详细长期记录将使麦克马斯特研究人员能够评估过去风暴的频率是否有所不同，以及风暴的变化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风暴频率的未来变化至关重要，并将有助于为加拿大东部人口稠密地区面临恶劣天气风险的地区制定适当的应急计划。