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Late Glacial Sea Level Minima in the Western British Isles

不列颠群岛西部的晚冰期海平面最低值

基本信息

批准号：
NE/H024069/1
负责人：
Antony Long
金额：
$ 27.15万
依托单位：
Durham University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2011
资助国家：
英国
起止时间：
2011 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FH024069%2F1
关键词：
Late Glacial Sea Level Minima

项目摘要

Relative sea level (RSL) change reflects the interplay between a large number of variables operating at scales from global to local. Changes in RSL around the British Isles (BI) since the height of the last glaciation (ca. 24 000 years ago), are dominated by two key variables (i) the rise of ocean levels caused by climate warming and the melting of land-based ice; and (ii) the vertical adjustment of the Earth's surface due to the redistribution of this mass (unloading of formerly glaciated regions and loading of the ocean basins and margins). As a consequence RSL histories vary considerably across the region once covered by the British-Irish Ice Sheet (BIIS). The variable RSL history means that the BI is a globally important location for studying the interactions between land, ice and the ocean during the profound and rapid changes that followed the last glacial maximum. The BI RSL record is an important yardstick for testing global models of land-ice-ocean interactions and this in turn is important for understanding future climate and sea level scenarios. At present, the observational record of RSL change in the British Isles is limited to shallow water areas because of accessibility and only the later part of the RSL curve is well studied. In Northern Britain, where the land has been rising most, RSL indicators are close to or above present sea level and the RSL record is most complete. In southern locations, where uplift has been less, sea level was below the present for long periods of time but there is very little data on RSL position. There are varying levels of agreement between models and existing field data and we cannot be certain of model projections of former low sea levels. Getting the models right is important for understanding the whole global pattern of land-ice-ocean interactions in the past and into the future. To gather the missing data and thus improve the utility of the British RSL curves for testing earth-ice-ocean models, we will employ a specialised, interdisciplinary approach that brings together a unique team of experts in a multidisciplinary team. We have carefully selected sites where there is evidence of former sea levels is definitely preserved and we will use existing seabed geological data in British and Irish archives to plan our investigations. The first step is marine geophysical profiling of submerged seabed sediments and mapping of surface geomorphological features on the seabed. These features include the (usually) erosional surface (unconformity) produced by the rise in sea level, and surface geomorphological features that indicate former shorelines (submerged beaches, barriers and deltas). These allow us to identify the position (but not the age) of lower than present sea levels. The second step is to use this stratigraphic and geomorphological information to identify sites where we will take cores to acquire sediments and organic material from low sea-level deposits. We will analyse the sediments and fossil content of the cores to find material that can be closely related to former sea levels and radiocarbon dated. The third step in our approach is to extend the observed RSL curves using our new data and compare this to model predictions of RSL. We can then modify the parameters in the model to obtain better agreement with observations and thus better understand the earth-ice-ocean interactions. These data are also important for understanding the palaeogeography of the British Isles. Our data will allow a first order reconstruction of former coastlines, based upon the modern bathymetry, for different time periods during the deglaciation. This is of particular importance to the presence or absence of potential landbridges that might have enabled immigration to Ireland of humans and animals. They will also allow us to identify former land surfaces on the seabed. The palaeogeography is crucial to understanding the evolving oceanographic circulation of the Irish Sea.

相对海平面（RSL）变化反映了从全球到局部尺度上的大量变量之间的相互作用。自最后一次冰期高峰（约2.4万年前）以来，不列颠群岛（BI）周围RSL的变化主要受两个关键变量(1)气候变暖和陆基冰融化引起的海平面上升；（ii）由于这些物质的再分配而导致的地球表面的垂直调整（以前冰川地区的卸载和海洋盆地和边缘的加载）。因此，在曾经被英爱冰原（BIIS）覆盖的地区，RSL的历史差异很大。可变的RSL历史意味着BI是研究末次极大期之后深刻而快速变化期间陆地、冰和海洋之间相互作用的全球重要地点。BI RSL记录是测试陆地-冰-海洋相互作用全球模型的重要尺度，这反过来对了解未来气候和海平面情景也很重要。目前，由于可达性的限制，对不列颠群岛RSL变化的观测记录仅限于浅水区，仅对RSL曲线的后期进行了较好的研究。在陆地上升最多的英国北部，RSL指标接近或高于目前的海平面，RSL记录最完整。在隆起较少的南部地区，海平面在很长一段时间内低于现在，但关于RSL位置的数据很少。模式与现有野外资料之间的吻合程度各不相同，我们不能肯定模式对以前低海平面的预估。正确的模型对于理解过去和未来陆地-冰-海洋相互作用的整个全球模式非常重要。为了收集缺失的数据，从而提高英国RSL曲线用于测试地球-冰-海洋模型的效用，我们将采用一种专门的跨学科方法，将多学科团队中的独特专家团队聚集在一起。我们仔细选择了有证据表明以前的海平面确实被保存下来的地点，我们将利用英国和爱尔兰档案中现有的海底地质数据来计划我们的调查。第一步是水下海底沉积物的海洋地球物理剖面和海底地表地貌特征的测绘。这些特征包括（通常）由海平面上升产生的侵蚀面（不整合面），以及表明以前海岸线的表面地貌特征（淹没的海滩、屏障和三角洲）。这使我们能够确定比现在海平面低的位置（但不是年龄）。第二步是利用这些地层学和地貌信息来确定我们将从低海平面沉积物中提取沉积物和有机物质的地点。我们将分析岩心的沉积物和化石含量，以找到与以前海平面和放射性碳年代密切相关的物质。我们方法的第三步是使用我们的新数据扩展观察到的RSL曲线，并将其与RSL的模型预测进行比较。然后，我们可以修改模型中的参数，以获得与观测结果更好的一致性，从而更好地了解地球-冰-海洋的相互作用。这些数据对于了解不列颠群岛的古地理也很重要。我们的数据将允许基于现代测深法，对冰川消融期间不同时期的前海岸线进行一级重建。这对于可能使人类和动物能够移民到爱尔兰的潜在陆桥的存在与否尤为重要。它们还将使我们能够识别海床上以前的陆地表面。古地理对于理解爱尔兰海的海洋环流演化至关重要。