Large-scale variation of deep cycle turbulence in the equatorial oceans and their influences on the SST and heat transport

The study will provide a comprehensive description of large-scale deep cycle turbulence (DCT) variation in the equatorial oceans. This will be achieved by using the state-of-the-art ocean general circulation model (OGCM) simulations with a suitable vertical mixing scheme that can be directly validated against microstructure measurements and is capable of reproducing characteristics of DCT. The influences of DCT on the sea surface temperature (SST) and upper ocean heat transport in the equatorial oceans across different timescales will be quantified, which play an essential role in tropical air-sea interactions and global weather and climate variability. Additionally, examining DCT modulated by various processes through sensitivity simulations will further advance our understanding of upper ocean mixing processes, leading to improved representation of these processes in the models. The project will investigate the spatiotemporal variation of DCT in the equatorial oceans and their influence on SST and heat transport based on integrated analysis of observational data and global OGCM simulations. A vertical mixing scheme that allows the modeled turbulent dissipation to be directly compared with that from microstructure measurements will be used in the OGCM simulations. Specific objectives include: Investigate the spatial variation of DCT on intraseasonal to seasonal timescales and its impact on SST and upper ocean heat transport in the equatorial Pacific Ocean. Determine the surface forcing and subsurface conditions that favor the DCT formation associated with the Madden-Julian Oscillation and examine the possible existence of DCT associated with the equatorial current system in the Indian Ocean. Investigate spatial distribution of DCT and its influence on the SST modulated by Tropical Instability Waves and seasonal freshwater discharge from the Amazon River in the equatorial Atlantic Ocean. 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.