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

• 批准号: NE/H024301/1
• 负责人: James Cooper
• 金额: $ 91.27万
• 依托单位: University of Ulster
• 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%2FH024301%2F1
• 关键词: Late; Glacial; Sea; Level; Minima

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运行的大量变量之间的相互作用。自末次冰川盛期（约 24000 年前）以来，不列颠群岛周围的 RSL（BI）变化主要由两个关键变量主导：（i）气候变暖和陆地冰融化引起的海平面上升； (ii) 由于质量的重新分布（以前冰川区域的卸载以及海洋盆地和边缘的加载）而导致的地球表面的垂直调整。因此，在曾经被英国-爱尔兰冰盖 (BIIS) 覆盖的地区，RSL 历史差异很大。可变的 RSL 历史意味着 BI 是研究末次盛冰期之后发生的深刻而快速的变化期间陆地、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标准，这反过来对于了解未来气候和海平面情景也很重要。目前，由于可及性的原因，对不列颠群岛RSL变化的观测记录仅限于浅水区，并且仅对RSL曲线的后期部分进行了深入研究。在土地上升幅度最大的英国北部，RSL 指标接近或高于目前的海平面，RSL 记录也最完整。在南部地区，由于抬升较少，海平面长期低于当前水平，但有关 RSL 位置的数据很少。模型与现有现场数据之间存在不同程度的一致性，我们无法确定模型对以前低海平面的预测。建立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 曲线在测试地球-冰-海洋模型中的实用性，我们将采用专门的跨学科方法，在多学科团队中汇集一支独特的专家团队。我们精心挑选了有证据表明以前的海平面确实得到保存的地点，我们将使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。第一步是对水下海底沉积物进行海洋地球物理剖面分析并绘制海底表面地貌特征。这些特征包括（通常）海平面上升产生的侵蚀面（不整合面），以及表明以前海岸线（水下海滩、屏障和三角洲）的地表地貌特征。这些使我们能够确定低于当前海平面的位置（但不是年龄）。第二步是利用这些地层和地貌信息来确定我们将在哪里取岩芯以从低海平面沉积物中获取沉积物和有机物质。我们将分析岩心的沉积物和化石含量，以寻找与以前的海平面和放射性碳测年密切相关的物质。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，从而更好地理解地球-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。我们的数据将允许根据现代测深技术，对冰消期不同时期的前海岸线进行一阶重建。这对于是否存在可能使人类和动物能够移民到爱尔兰的潜在陆桥尤为重要。它们还将使我们能够识别海底以前的陆地表面。古地理对于理解爱尔兰海不断演变的海洋环流至关重要。

项目成果

Measuring the most complicated post-glacial sea-level changes in the world: Northern Ireland

测量世界上最复杂的冰川后海平面变化：北爱尔兰

• 发表时间: 2018
• 作者: Kelley, J.T.

Offshore evidence of postglacial relative sea-level change from eastern Ireland.

爱尔兰东部冰期后相对海平面变化的近海证据。

• 发表时间: 2014
• 期刊: EGU General Assembly Conference Abstracts
• 作者: Callard S. Louise

Late glacial sea level minima in the Western British Isles: observed and modelled.

不列颠群岛西部的晚冰期海平面最低点：观察和模拟。

• 作者: James Cooper (Author)

New observations on relative sea-level change since the late Glacial from the British and Irish continental shelf and their implications for understanding earth-ice-ocean interactions

英国和爱尔兰大陆架自晚冰期以来相对海平面变化的新观测及其对理解地球-冰-海洋相互作用的影响

• 发表时间: 2013
• 期刊: AGU Fall Meeting Abstracts
• 作者: Cooper J. A.

SUBMERGED SHORELINES IN THE IRISH SEA: SPATIAL VARIABILITY IN FORM AND PRESERVATION

爱尔兰海淹没的海岸线：形态和保护的空间变化

• 作者: James Cooper (Author)