- Carl von Ossietzky Universität Oldenburg, Institute for Chemistry and Biology of the Marine Environment, Wilhelmshaven, Germany (lisa.deyle@uni-oldenburg.de)
The near-surface ocean is central to exchanging energy, gases, and particles between the atmosphere and the upper ocean. In particular, the interaction processes between the sea surface microlayer and the underlying water are crucial for biogeochemical processes and climate science. An innovative approach using free-floating, minimal-invasive Lagrangian sensor drifters is employed to investigate hydrographic and dynamical processes in the near-surface layer. Each drifter is equipped with a sensor chain containing temperature and salinity sensors, enabling high-resolution vertical measurements down to a depth of 1.8 m.
The Lagrangian measurement method enables the dynamics of a water mass to be recorded in its natural inertial system without external influences such as ship-induced disturbances. During a field campaign in the North Sea near Helgoland in July 2024, temperature and salinity data were collected during slick events associated with algal blooms. Processes inside and outside the slicks, as well as their formation, dispersion and decay processes, were studied to understand the underlying mechanisms. This allows the analysis of horizontal and vertical gradients, as well as the investigation of the spatial and temporal dynamics of slicks, understanding their impact on the exchange processes and quantifying the importance of the sea surface microlayer and the underlying water.
Initial results reveal significant differences in temperature and salinity gradients between slick and non-slick areas. Slicks act as hydrodynamic microhabitats and critical boundaries, influencing vertical convection patterns and current shear in the near-surface layer. These results are confirmed by ADCP backscatter data collected from an autonomous catamaran, providing additional insights into current structures and particle distributions. Horizontal comparisons between multiple sensor-equipped drifters illustrate the variability of processes at small spatial scales.
The presented results demonstrate the potential of Lagrangian drifters as a minimally invasive, innovative and highly accurate method for studying slicks and climate-relevant processes in the near-surface layer. These approaches can significantly improve our understanding of air-sea interaction mechanisms and their role in global biogeochemical cycles.
How to cite: Deyle, L., Albinus, M., Meyerjürgens, J., and Badewien, T. H.: Hydrodynamic Processes and Temperature-Salinity Gradients in Slicks: Insights from Lagrangian Observations in the Near-Surface Layer, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15118, https://doi.org/10.5194/egusphere-egu25-15118, 2025.