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Meteorological Conditions Influence the Migration of a Marine Dune Field in the Southern North Sea.

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Title: Meteorological Conditions Influence the Migration of a Marine Dune Field in the Southern North Sea.
Authors: Durand, Noémie1,2 (AUTHOR) noedurand@openbook.team, Tassi, Pablo2,3 (AUTHOR), Blanpain, Olivier1 (AUTHOR), Lefebvre, Alice4 (AUTHOR)
Source: Journal of Geophysical Research. Earth Surface. Jan2025, Vol. 130 Issue 1, p1-27. 27p.
Subject Terms: *Atmospheric pressure, *Sand dunes, Tidal currents, Wind pressure, Tidal forces (Mechanics)
Abstract: A field of marine dunes has been studied in the Southern Bight of the North Sea. These large dunes, 1–5 m in height and several hundred meters in length, are highly mobile: migration rates of up to 30 m/year have been observed in places. The area is dominated by tides and is characterized by strong currents. Winds are predominantly from the southwest and, to a lesser extent, from the north. A large‐scale 3D numerical model was used to simulate the migration of this dune field over time. It is based on the process‐based opentelemac system. The model has been calibrated and validated against in situ bathymetric data and is therefore suited to our objective: to explore the contribution of weather (wind and atmospheric pressure) to the propagation of large marine dunes, in relation to that of tidal currents. To do this, a 4‐month period was simulated, with and without meteorological effects being taken into account in the numerical model. The results highlight the fundamental role of wind conditions in an accurate representation of seabed changes over time. They also show how meteorological events that are different from the prevailing conditions influence the short‐term evolution of the dune field. Plain Language Summary: Marine dunes are large sedimentary formations, typically 1–5 m high, which run transversely to the flow and are highly mobile. They are found all over the world, in a wide variety of environments, including in shallow shelf seas such as the North Sea. Their presence poses problems for marine renewable energy projects located there. It is therefore crucial to be able to simulate their evolution over time. A large‐scale computer model has been developed to represent a field of marine dunes off the coast of Dunkirk, France. The model reproduces the migration observed after 4 months. It was then run with the tide alone and with the tide + meteorological effects. This allows us to determine the contribution of wind‐induced currents compared with tide‐induced currents to the dynamics of large marine dunes. The results show that the migration of the marine dunes is intimately related to the amplitude and direction of the residual flow, which are influenced by wind conditions. Meteorological forcing is necessary to obtain an accurate representation of seabed changes over time. Although winds that are different from the prevailing winds may temporarily reverse the general migration trend, they are too sporadic to fundamentally alter the sedimentary dynamics of the area. Key Points: A numerical model is developed and applied to a real site to study the propagation of marine dunes for the first time in 3D on a large scaleUnder real‐life conditions wind forcing is shown to have just as great an effect on dune migration as tidal forcingCounter‐prevailing winds can temporarily reverse the migration of large marine dunes while maintaining their asymmetry [ABSTRACT FROM AUTHOR]
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Abstract:A field of marine dunes has been studied in the Southern Bight of the North Sea. These large dunes, 1–5 m in height and several hundred meters in length, are highly mobile: migration rates of up to 30 m/year have been observed in places. The area is dominated by tides and is characterized by strong currents. Winds are predominantly from the southwest and, to a lesser extent, from the north. A large‐scale 3D numerical model was used to simulate the migration of this dune field over time. It is based on the process‐based opentelemac system. The model has been calibrated and validated against in situ bathymetric data and is therefore suited to our objective: to explore the contribution of weather (wind and atmospheric pressure) to the propagation of large marine dunes, in relation to that of tidal currents. To do this, a 4‐month period was simulated, with and without meteorological effects being taken into account in the numerical model. The results highlight the fundamental role of wind conditions in an accurate representation of seabed changes over time. They also show how meteorological events that are different from the prevailing conditions influence the short‐term evolution of the dune field. Plain Language Summary: Marine dunes are large sedimentary formations, typically 1–5 m high, which run transversely to the flow and are highly mobile. They are found all over the world, in a wide variety of environments, including in shallow shelf seas such as the North Sea. Their presence poses problems for marine renewable energy projects located there. It is therefore crucial to be able to simulate their evolution over time. A large‐scale computer model has been developed to represent a field of marine dunes off the coast of Dunkirk, France. The model reproduces the migration observed after 4 months. It was then run with the tide alone and with the tide + meteorological effects. This allows us to determine the contribution of wind‐induced currents compared with tide‐induced currents to the dynamics of large marine dunes. The results show that the migration of the marine dunes is intimately related to the amplitude and direction of the residual flow, which are influenced by wind conditions. Meteorological forcing is necessary to obtain an accurate representation of seabed changes over time. Although winds that are different from the prevailing winds may temporarily reverse the general migration trend, they are too sporadic to fundamentally alter the sedimentary dynamics of the area. Key Points: A numerical model is developed and applied to a real site to study the propagation of marine dunes for the first time in 3D on a large scaleUnder real‐life conditions wind forcing is shown to have just as great an effect on dune migration as tidal forcingCounter‐prevailing winds can temporarily reverse the migration of large marine dunes while maintaining their asymmetry [ABSTRACT FROM AUTHOR]
ISSN:21699003
DOI:10.1029/2024JF007731