Sedimentary Records of Past Marine Environments

海洋沉积物是宝贵的气候档案，记录了各种环境信息，有助于提高我们对海洋-大气系统的认识。然而，目前的许多研究认为，大部分沉积物只是作为信息提供者的载体，例如浮游生物的化石遗骸。这种忽略大块沉积物及其大小特征的方法导致a)对某些地区海洋沉积记录的解释含糊不清；b)丢失了有关海底沉积环境的宝贵信息。在本提案中，我们通过研究现有沉积物岩心的粒度组成来解决这个问题。我们的方法是基于粒径在10-63微米之间的颗粒（泥沙）的已知行为，这些颗粒是根据底部电流的速度进行大小排序的。在目前对沉积记录的解释存在争议的赤道东太平洋地区，粒度分析将与地球化学测量相结合，以准确量化与气候有关的物质（如碳酸盐、有机物）从海面到海底的通量。这将使我们能够确定底流的横向沉积物运动是否对该地区以前的解释产生了偏差。关于赤道太平洋过去行为的可靠数据对于更好地了解太平洋在从年际（即El-Niño）到冰期-间冰期等时间尺度上对全球气候变化所起的作用至关重要。在离我们更近的地方，在苏格兰大陆架上，我们正在使用同样的方法，但目标不同。在这里，人们认为风暴会使海床上的沙粒悬浮起来，并将它们重新沉积在其他地方有特色的海床上。通过分析战略性地点的羽绒岩芯粒度组成，我们将生成过去一万年的风暴记录。这一记录将大大扩展仪器记录，并有助于改进对未来风暴的预测。由于预计风暴将对大西洋沿岸的人们和基础设施产生越来越大的影响，这项研究将直接造福加拿大。

Marine sediments are valuable climate archives and record diverse types of environmental information, which is used to improve our understanding of the ocean-atmosphere system. However, many current studies consider the bulk of the sediment only as the carrier for the information provider, such as fossil remains of plankton. This approach of ignoring the bulk sediment and its size characteristics has led to a) ambiguity in the interpretation of the marine sedimentary record in some areas and b) a loss of valuable information about the depositional environment on the sea floor. In this proposal, we address this issue by investigating the grain size composition of existing sediment cores. Our approach is based on the known behaviour of particles between 10-63 micrometer in size (silts), which are size-sorted according to bottom current speed. In the eastern equatorial Pacific, an area where current interpretations of the sedimentary record are controversial, grain size analyses will be combined with geochemical measurements to accurately quantify the flux of climate relevant material (e.g. carbonate, organic matter) from the sea surface to the sea floor. This will enable us to determine whether or not lateral sediment movement by bottom currents has biased previous interpretations in this region. Reliable data on the past behaviour of the equatorial Pacific are crucially important for a better understanding of the role that the Pacific plays in global climate change on time-scales ranging from interannual (i.e. El-Niño) to glacial-interglacial. Closer to home, on the Scotian Shelf, we are using the same approach with a different goal. Here, storms are thought to resuspend sand grains from the sea bed and redeposit them in characteristic beds elsewhere. By analysing the down core grain size composition of strategically located sites, we will generate a record of storminess over the last 10,000 years. This record will significantly extend the instrumental record and contribute to improving projections of storms in the future. As storms are expected to have an ever increasing impact on people and infrastructure along the Atlantic coast, this research will be of direct benefit to Canada.