Ocean Dynamics Impacting Shelf Sea Level in Eastern Atlantic (ODISSEA)

由于陆地冰融化和海洋热膨胀的共同作用，全球平均海平面正以每年3.5毫米的速度上升。然而，从区域来看，海平面也受到大尺度洋流强度和路径变化的强烈影响，长期趋势往往被几年的大幅度变化所掩盖。对沿海社区来说，量化和预测区域模式至关重要，因为极端海平面事件的规模和频率与社会直接相关。在美国东海岸，海平面上升和变化模式与大西洋经向翻转环流（AMOC）密切相关。然而，在西北欧洲大陆架上，人们对AMOC对海平面变化、变率和极端事件的影响知之甚少。实现这一目标的一个关键障碍是了解大陆斜坡上的海洋动力学——大陆斜坡是深海和浅大陆架之间的界面。从深海流向斜坡的水流可能不会继续流到大陆架上，而可能会流入环绕欧洲大陆架西北部的沿坡边界的快速水流。了解这些过程的相对重要性，以及它们如何随时间变化，是了解海岸海平面如何变化的关键。据预测，随着气候变暖，大规模洋流将发生变化，AMOC预计将在未来30年急剧减弱。然而，产生这些预测的气候模式缺乏所需的精细分辨率，无法在区域尺度上捕捉这些变化对陆架海平面的影响，特别是窄边界流在调节海岸深海环流影响方面的作用。因此，如果要有效地预测不断变化的洋流对沿海海平面的影响，就必须充分了解边界流动力学。在这个项目中，我们将直接测量从公海流向西北大陆架的水流，以及测量边界流强度和大陆架海平面。这将使我们能够确定边界动力学在调节陆架海平面海洋环流效应中所起的作用。我们还将使用该地区的实验模拟来量化起作用的物理过程，并了解这些过程在更长的时间尺度上是如何变化的。最后，我们将运行一个高分辨率的未来大西洋模拟，研究这些过程将如何随着AMOC在未来30年的减弱而演变，并评估对沿海海平面变化、变率和极端事件的影响。

Global mean sea level is rising at around 3.5 mm per year due to the combined effects of melting land ice and ocean thermal expansion. Regionally however, sea level is also strongly influenced by changes in the strength and the pathways of large-scale ocean currents, and the long-term trend is often masked by large-amplitude changes over several years. Quantifying and predicting regional patterns is crucial for coastal communities where the magnitude and frequency of extreme sea level events are of immediate societal relevance. At the U.S. East Coast, sea level rise and variability patterns have been strongly linked to the Atlantic meridional overturning circulation (AMOC). However, on the NW European shelf, comparatively little is known about the impact of AMOC on sea level change, variability, and extremes.A key barrier to achieving this is understanding the ocean dynamics over the continental slope - the interface between the deep ocean and the shallow continental shelf. Currents directed from the deep ocean towards the slope might not continue onto the shelf and might instead feed into the rapid along-slope boundary current which encircles the NW European shelf. Understanding the relative importance of each of these processes, and how they change over time, is key to understanding how sea level will change at the coast.Large scale ocean currents are predicted to change with the warming climate, with the AMOC projected to weaken dramatically in the next 30 years. However, the climate models which yield these predictions lack the fine-scale resolution required to capture the effect of these changes on shelf sea level at a regional scale, in particular the role of narrow boundary currents in modulating the influence of the deep ocean circulation at the coast.It is therefore critical that boundary current dynamics are fully understood if the effect of changing ocean currents on coastal sea level is to be effectively predicted. In this project, we will directly measure the flow directed from the open ocean towards the NW European shelf, as well as measuring the boundary current strength and shelf sea level. This will allow us to establish the role that boundary dynamics play in modulating the effect of ocean circulation of shelf sea level. We will also use experimental simulations of the region to quantify the physical processes at play and understand how these change over longer time scales. Finally, we will run a high-resolution future Atlantic Ocean simulation to study how these processes will evolve as the AMOC weakens during the next three decades, and evaluate the impacts on coastal sea level change, variability, and extremes.