CAREER: Small Fronts in the Vast Sea - Multiscale Dynamics and Impact of Submesoscale Density Fronts

About This Grant

Submesoscale density fronts at the ocean’s surface are just hundreds of meters to tens of kilometers in width, however they are thought to have a substantial impact on the exchange of heat and other properties in and near the mixed layer, contribute to across-scale energy transfers, and consequently play a role in modulating chemical and biological processes in the surface ocean. This study will use existing shipboard observations of surface temperature and salinity along with satellite imagery to study global patterns in submesoscale variability. This research has the potential to expand our knowledge of the dynamics, seasonality, and impact of submesoscale density fronts to encompass the global scale. This is currently an underdeveloped area of research since the majority of observational studies of oceanic submesoscale fronts focus on individual fronts or specific regions. Improving our global understanding of submesoscale fronts may inspire future observational process studies in new regions of the world, motivate future theory and modeling studies that focus on currently under-studied regimes, and give rise to improved submesoscale parameterizations. The research component will support a graduate student for 5 years. The educational component of this CAREER award will introduce 9 undergraduate art students to scientific research. The art students will be fully involved in the science-based activities, and will be advised by both scientists and artists throughout their science-inspired summer projects. This will help train the next generation of science communicators while introducing a total of about 45 undergraduate science students to the importance of creativity in science. Despite the indication from modeling studies that submesoscale frontal dynamics have a global-scale impact, the majority of observational work has focused on individual fronts or specific regions of the world ocean. This gap is due to the inherit challenges in collecting and interpreting multiscale measurements that include length scales spanning both the frontal and global scale. To fill this gap, a new method was recently developed by the lead investigator of this project that uses a global ship-based thermosaliniograph dataset and high resolution satellite sea surface temperature data to detect submesoscale density fronts, determine their widths, and calculate their cross-front horizontal buoyancy gradients. This project uses this frontal detection method, combined with additional global datasets, to target three open research areas: A) The submesoscale plays a critical role in the seasonal evolution of mixed layer depth and, subsequently, air-sea exchange. This study will explore the global seasonal cycle of submesoscale frontal dynamics, determining how and why the seasonal cycle varies regionally. B) The local mesoscale velocity field and wind stress is known to impact submesoscale dynamics. This project will investigate if the mesoscale vorticity, mesoscale strain rate, and wind stress modulates submesoscale dynamics globally in a way that is consistent with existing theories. C) The conversion of potential energy stored in the wintertime mixed layer to kinetic energy in submesoscale fronts and eddies is critical for cross-scale energy exchange during springtime restratification. This project plans to quantify this energy conversion rate globally and seasonally. These results will then be placed within the broader cross-scale energetic context. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.