Particle tracking in the vicinity of Helgoland, North Sea: a model comparison

• Published in: Ocean dynamics Vol. 61; no. 12; pp. 2121 - 2139
• Main Authors: Callies, Ulrich, Plüß, Andreas, Kappenberg, Jens, Kapitza, Hartmut
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.12.2011; Springer Nature B.V
• Subjects: Atmospheric forcing; Atmospheric Sciences; Atoms & subatomic particles; Boundary conditions; Comparative studies; Earth and Environmental Science; Earth Sciences; Fluid- and Aerodynamics; Geophysics/Geodesy; Marine; Monitoring/Environmental Analysis; Oceanography; Topical Collection on Maritime Rapid Environmental Assessment; North Sea; ANE, North Sea; ANE, Germany, Schleswig-Holstein, North Frisian Is., Helgoland; ANE, Germany, German Bight; Helgoland Roads; Lagrangian particle tracking; Model comparison; North Sea; Backward trajectories
• ISSN: 1616-7341; 1616-7228
• DOI: 10.1007/s10236-011-0474-8

Station Helgoland Roads in the south-eastern North Sea (German Bight) hosts one of the richest long-term time series of marine observations. Hydrodynamic transport simulations can help understand variability in the local data brought about by intermittent changes of water masses. The objective of our study is to estimate to which extent the outcome of such transport simulations depends on the choice of a specific hydrodynamic model. Our basic experiment consists of 3,377 Lagrangian simulations in time-reversed mode initialized every 7 h within the period Feb 2002–Oct 2004. Fifty-day backward simulations were performed based on hourly current fields from four different hydrodynamic models that are all well established but differ with regard to spatial resolution, dimensionality (2D or 3D), the origin of atmospheric forcing data, treatment of boundary conditions, presence or absence of baroclinic terms, and the numerical scheme. The particle-tracking algorithm is 2D; fields from 3D models were averaged vertically. Drift simulations were evaluated quantitatively in terms of the fraction of released particles that crossed each cell of a network of receptor regions centred at the island of Helgoland. We found substantial systematic differences between drift simulations based on each of the four hydrodynamic models. Sensitivity studies with regard to spatial resolution and the effects of baroclinic processes suggest that differences in model output cannot unambiguously be assigned to certain model properties or restrictions. Therefore, multi-model simulations are needed for a proper identification of uncertainties in long-term Lagrangian drift simulations.