Comment on gmd-2022-104

Abstract

Gyres and eddies, i.e., large-scale rotating coherent water masses, are prominent features of large lakes and oceans, are formed due to the interplay between Coriolis force and wind stress. Understanding their dynamics is important as they are known to play a crucial role in spreading bio-chemical materials and energy throughout lakes and oceans. Since field observations in large lakes are sparse in time and location, often limited to a few moorings, they cannot provide a comprehensive validation dataset for such large-scale current systems. Previous numerical studies suggested the presence of different and complex gyre systems in many large lakes, however none were confirmed with detailed field measurements. In order to assess the spatial and temporal extent of gyres and eddies, their dynamics and vertical structure, as well as validate their prediction in numerical simulation results, transect field observations should be carried out. However, at present it is difficult to forecast when and where such transect field observations should be taken. To overcome this problem, a novel procedure combining 3D numerical simulations, statistical analyses, and remote sensing data was developed that permits determination of the spatial and temporal patterns of basin-scale gyres during different seasons. The efficiency and robustness of the proposed procedure was validated in Lake Geneva. For the first time in a lake, detailed field evidence of the existence of basin-scale gyres and (sub)mesoscale eddies was provided by data collected along transects whose locations were predetermined by the proposed procedure. The close correspondence between field observations and detailed numerical results further confirms the validity of the model for capturing large-scale current circulations as well as submesoscale eddies. The procedure can be applied to other large lakes and can be extended to the interaction of biological-chemical-physical processes.