Abstract

Wintertime sea level variability over the northern European continental shelf is largely wind-driven. Using daily gridded sea level anomaly from altimetry, we examine both the spatial and the temporal relationship between northern European sea level variability and large-scale atmospheric circulation patterns as represented by the jet cluster paradigm. The jet clusters represent different configurations of the eddy-driven jet stream and, therefore, provide a physical description of the atmospheric variability in the North Atlantic. We find that each of the four jet clusters is associated with a distinct northern European sea level anomaly pattern whose magnitudes are comparable to those of typical sea level variations on the shelf. In certain locations, such as the German Bight and the east coast of England, sea level anomalies are mainly associated with one single jet cluster. In other locations, such as the interior and the northern part of the North Sea, sea level anomalies are found to be sensitive to at least two jet configurations. Based on these regional sea level variations, we map out the locations on the shelf where each jet cluster or combination of clusters is most active before discussing the role of Ekman transport in inducing the resulting patterns. Through a multiple linear regression model, we also find that the jet clusters reconstruct up to 50% of the monthly mean sea level anomaly variance over the northern European continental shelf. The model best performs in the interior and the western part of the North Sea, suggesting that wind direction rather than wind speed plays a more prominent role over these regions. We conclude that the jet cluster approach gives valuable new insights compared to linear regression techniques for characterising wind-driven sea level variability over the northern European continental shelf.

摘要

北欧大陆架的冬季海平面变化很大程度上是由风驱动的。利用来自测高的每日网格海平面异常，我们检查了北欧海平面变化与以喷射星团范式为代表的大规模大气环流模式之间的时空关系。射流簇代表涡流驱动射流的不同配置，因此，提供了北大西洋大气变化的物理描述。我们发现，四个喷流簇中的每一个都与一个独特的北欧海平面异常模式有关，其异常幅度与陆架上典型海平面变化的幅度相当。在某些地区，例如德国湾和英格兰东海岸，海平面异常主要与单个喷气机群有关。在其他位置，例如北海的内部和北部，发现海平面异常对至少两个射流构型敏感。基于这些区域性海平面变化，我们在讨论埃克曼运输在诱导最终模式中的作用之前，先绘制出每个喷气流簇或簇群最活跃的架子位置。通过多元线性回归模型，我们还发现，在北欧大陆架上，喷流团簇最多重构了月平均海平面异常方差的50％。该模型在北海的内陆和西部地区表现最佳，表明在这些地区，风向而非风速起着更为重要的作用。