Publikasjoner
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Magana, Rosa Maria Vargas; Kalisch, Henrik; Buckley, Marc; Bjørnestad, Maria; Gronemann, Tessa Doreen & Holand, Karoline
[Vis alle 9 forfattere av denne artikkelen]
(2026).
Lagrangian Acceleration as a Diagnostic for Wave Breaking in the Nearshore Zone.
Journal of Geophysical Research (JGR): Oceans.
ISSN 2169-9275.
131(3),
s. 1–17.
doi:
10.1029/2024JC022193.
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This study focuses on evaluating the Lagrangian downward acceleration of fluid particles near the wavecrest as a dynamic criterion for identification of wave breaking in shallow water. The use of the downward acceleration as an indicator for wave breaking goes back to the work of Longuet‐Higgins (1963), https://doi.org/10.1017/s0022112063000641 who showed theoretically that the acceleration near the crest of a regular wave is -0.5g for the highest wave in deep water. In the subsequent literature, various other threshold values on the downward acceleration have been suggested based on theoretical or experimental investigations but a general agreement has not been established. Based on stereo imaging of tracer particles in the surf at Sylt, Germany, data analysis, and in‐depth visual analysis, it is shown here that this criterion successfully classifies breaking and non‐breaking waves in 96% of the 99 wave events examined.
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Bjørnestad, Maria; Halsne, Trygve; Malila, Mika Petteri; Benetazzo, Alvise; Bergamasco, Filippo & Pistellato, Mara
[Vis alle 11 forfattere av denne artikkelen]
(2025).
Whitecaps, Bubbles and Advection: Insights From Concurrent Measurements in the Open Ocean.
Geophysical Research Letters.
ISSN 0094-8276.
52(21).
doi:
10.1029/2025gl117684.
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Field measurements of breaking waves and bubble depths were obtained using a stereo video system collocated with a submerged acoustic Doppler current profiler (ADCP) in the central North Sea. We discriminate between two bubble depths that define an active near‐surface layer and a deeper layer. The active layer intermittently sees short‐lived injected bubble depths from breakers whereas the deeper layer is dominated by persistent passive bubble plumes that remain visible for more than 50 mean wave periods. We augment traditional single‐beam bubble detection methods by utilizing all five beams of the ADCP to achieve broader spatial coverage of bubble plume measurements. The combined wave and bubble observations reveal that deep bubble plumes often occur offset spatially from surface whitecaps, suggesting that Langmuir‐type circulation plays a role in the formation and persistence of deep bubble plumes through vertical and horizontal advection.
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Jacobsen, Andreas Bondehagen; Roeber, Volker; Kalisch, Henrik; Buckley, Marc P.; Streßer, Michael & Cysewski, Marius
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(2024).
Wave-driven current and vortex patterns at an open beach: Insights from phase-resolving numerical computations and Lagrangian measurements.
Coastal Engineering.
ISSN 0378-3839.
193,
s. 1–16.
doi:
10.1016/j.coastaleng.2024.104591.
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Wave-driven currents have a substantial impact on local circulation patterns in and across the surf zone, and are responsible for cross-shore and longshore exchange of mass and momentum over a broad range of spatial and temporal scales. Nearshore currents may drive sediment transport, lead to beach erosion, and also affect the spread of bacteria and other marine microorganisms, as well as the distribution of pollutants such as chemicals and microplastics. In addition, surf zone currents can cause hazardous conditions for beach-goers in the form of rip currents. It is known from previous work (Chen et al., 2003; Feddersen et al., 2011; Hally-Rosendahl and Feddersen, 2016) that Boussinesq-type models in combination with appropriate boundary conditions and wave breaking capabilities can function as powerful tools for the analysis of circulation patterns in the surf zone. In the present work, data from a recent field campaign reported on in Bjørnestad et al. (2021) are used to further validate the capability of Boussinesq systems to simulate nearshore dynamics. The numerical model is then used to study the influence of tidal elevation, peak direction and directional spread of the incoming wavefield on the quantity, extent, and circulatory magnitude of the nearshore circulation. In addition, fundamental features such as horizontal eddies are investigated, and comparisons are made to solid-body rotation and irrotational vortices. Overall, it is observed that local variations in the bathymetry across the surf zone are the controlling factor regarding the size of these circulations, and an increasing tidal level, which can be seen as a uniform offset to the bathymetry, favors the generation of larger vortex patterns. For a given tidal stage, the directional spread of the incoming wavefield has the most pronounced influence on the size and strength of the nearshore eddies while the peak direction has the strongest effect on the total number of circulations.
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Bjørnestad, Maria; Buckley, M.; Kalisch, Henrik; Streßer, M.; Horstmann, J. & Frøysa, Hege Guldbrandsen
[Vis alle 9 forfattere av denne artikkelen]
(2021).
Lagrangian Measurements of Orbital Velocities in the Surf Zone.
Geophysical Research Letters.
ISSN 0094-8276.
48(21),
s. 1–9.
doi:
10.1029/2021GL095722.
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Eulerian and Lagrangian measurements of orbital velocities in waves approaching a beach are analyzed with the goal of understanding the relative influence of wave-by-wave variations in mean-water level, wave height and incipient wave breaking on mass transport properties of waves in the surf zone. It is shown quantitatively that elevated local mean-water level correlates positively with increased Lagrangian mass transport at the free surface. Eulerian ADV measurements in the fluid column suggest that the depth-integrated wave-by-wave mass transport also correlates positively with the local mean-water level, and is only weakly linked to wave height and wave-breaking events.
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Bjørnestad, Maria; Kalisch, Henrik; Abid, Malek; Kharif, Christian & Brun, Mats
(2021).
Wave Breaking in Undular Bores with Shear Flows.
Water Waves.
ISSN 2523-367X.
3,
s. 473–490.
doi:
10.1007/s42286-020-00046-6.
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It is well known that weak hydraulic jumps and bores develop a growing number of surface oscillations behind the bore front. Defining the bore strength as the ratio of the head of the undular bore to the undisturbed depth, it was found in the classic work of Favre (Ondes de Translation. Dunod, Paris, 1935) that the regime of laminar flow is demarcated from the regime of partially turbulent flows by a sharply defined value 0.281. This critical bore strength is characterized by the eventual breaking of the leading wave of the bore front. Compared to the flow depth in the wave flume, the waves developing behind the bore front are long and of small amplitude, and it can be shown that the situation can be described approximately using the well known Kortweg–de Vries equation. In the present contribution, it is shown that if a shear flow is incorporated into the KdV equation, and a kinematic breaking criterion is used to test whether the waves are spilling, then the critical bore strength can be found theoretically within an error of less than ten percent.
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Bjørnestad, Maria & Kalisch, Henrik
(2020).
Extreme wave runup on a steep coastal profile.
AIP Advances.
10(10),
s. 105205-1–105205-7.
doi:
10.1063/5.0020128.
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It is shown that very steep coastal profiles can give rise to unexpectedly large wave events at the coast. We combine insight from exact solutions of a simplified mathematical model with photographs from observations at the Norwegian coast near the city of Haugesund. The results suggest that even under moderate wave conditions, very large run-up can occur at the shore.
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Bjørnestad, Maria & Kalisch, Henrik
(2017).
Shallow water dynamics on linear shear flows and plane beaches.
Physics of Fluids.
ISSN 1070-6631.
29(7).
doi:
10.1063/1.4994593.
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Publisert
10. sep. 2026 05:53
- Sist endret
6. okt. 2026 12:47