Project Details
Projekt
SP 2.3 - Dynamics of convection linking the sea-surface microlayer (SML) with the bulk phase
Subject Area
Oceanography
Term
since 2022
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 451574234
Our motivation lies in the fact that the dynamic link between the sea-surface microlayer (SML) and underlying bulk water via convection leads to heterogeneous properties of the SML. This in turn controls the extent of bio-photochemical reactions and air-sea gas fluxes. Convection is driven by evaporation, which cools the SML and makes it more saline. Consequently, the SML becomes denser, sinks, and is replaced by underlying bulk water. However, buoyancy-driven convection has been neglected in the research of the SML and air-sea gas exchange as a dynamic link between the atmosphere and the ocean. Our main objective is to obtain a mechanistic understanding of the dynamics between the SML and the near-surface layer (NSL). One of the main points of our proposal is that buoyancy-driven convection is a key component of the SML and air-sea interaction, despite its small-scaled nature. A mechanistic understanding of convection is essential, as the extent of bio-photochemical reactions and the air-sea exchange of trace gases, energy, and momentum will ultimately be determined by exchange processes between the SML and the NSL, and ultimately with deeper layers. We will develop an experimental setup with multiple profiling microelectrodes and an optical schlieren system to investigate convection under various external forcing. We will investigate the effect of horizontal flow due to gradients of surface tension (i.e. Marangoni effect). We will also participate in the BASS joint mesocosm experiment to investigate the influence of biogenic surfactants on the convective transport mechanism between the SML and the NSL. In the BASS joint field experiment, we will address the question to what extent variations of small-scaled convection are affected by the variability of sub-mesoscale (1 km–10 km) hydrodynamic processes near the ocean’s surface. We will deploy two research catamarans and a fleet of drifters equipped with conductivity and temperature sensors to investigate density anomalies between the SML and NSL. We will monitor external oceanic and atmospheric forcing to describe the density anomalies. Finally, we will use the gained knowledge from the lab experiments, mesocosm, and field study to develop a mathematical framework to describe temperature and salinity profiles, and their fluctuations under the influence of defined oceanic and atmospheric forcing.
DFG Programme
Research Units
