Understanding flows and sediment dynamics in the Norwegian Trench: Insights from the RV Pelagia Expedition 2023

The Norwegian Trench and Skagerrak form a major canyon that cuts through the Northern North Sea towards the Kattegat. The Norwegian Trench and Skagerrak influence the inflow of Atlantic Water into the northern North Sea and the outflow of fresher waters from the Baltic and the many river plumes around the North Sea that flow towards the Atlantic Ocean through the Norwegian Coastal Current (NCC). The Norwegian Trench and Skagerrak have a key role to play in the circulation, transport and exchange of freshwater and sediment, having a strong control on the circulation, water mass transformations and sediment dynamics in the northern North Sea. When the NCC interacts with the saline waters of the North Atlantic large mesoscale eddies from and dominate the circulation. We explore how these eddies interact with the flow around the canyon, and influence the exchange between the North Sea and the Atlantic Ocean. To do this we use unique observations from the Norwegian Trench taken aboard the research vessel Pelagia between May 26th and June 14th 2023 together with numerical models of the region. Uniquely the data include Conductivity Temperature Depth (CTD) measurements, velocities, box core samples and multicore samples from stations in the Norwegian Trench. It also includes results from onboard erosion experiments. Additionally, Argo float data highlight the large-scale circulation in the northern North Sea. We explore whether the high current velocities at the seafloor could be induced by eddies and topographically steered currents and their impact on sediment dynamics.