Changing Atlantic influences on Northwest European shelf seas.

• Main Author: Clark, Matt
• Format: Thesis
• Language: English
• Published: University of Southampton 2023
• Subjects: north atlantic current; North Atlantic
• Online Access: https://eprints.soton.ac.uk/479530/; https://eprints.soton.ac.uk/479530/1/Thesis.V3.0.1.MPC.Archive.pdf; https://eprints.soton.ac.uk/479530/2/Final_thesis_submission_Examination_Mr_Matthew_Clark.pdf

The North Atlantic Ocean is highly dynamic. Its physical, biological, and chemical characteristics change across multiple timescales: from daily to inter-decadal and beyond. Surface oceanic flows in this region are dominated by the sub-polar and sub-tropical gyres, with the North Atlantic Current running between the two. Changes to these flows and the properties of conveyed North Atlantic water are not only felt in the ocean basin, but at the oceanic boundaries. The eastern boundary is adjacent to the northwest European shelf seas, and the location of a northward flowing shelf edge current commonly known as the European Slope Current. The shelf seas and this Slope Current are strongly affected by eastward geostrophic flows traced back to a combination of subtropical and subpolar sources. With the surface layers of the North Atlantic warming by nearly 2 °C over the past 4 decades, the density gradients that maintain these eastward flows have decreased, which has reduced the shelf edge flow on the order of 5 Sv. Atlantic inflow to the North Sea is directly related to the strength of the northward Slope Current transport. This inflow has reduced and acted to increase the residence time of Atlantic water in the North Sea by up to 100 days. Atlantic inflow provides the main nutrient flux to the North Sea. A reduction in this flux has implications for the productivity of the region, which remains an important fishery for the UK. In summary, basin-scale changes in physical properties reverberate at the shelf break flows and in the shelf seas, which in turn affect nutrient fluxes and primary production in the region.