Mixing Induced Vertical Heat and Freshwater Fluxes in the Upper Ocean of the Subpolar North Atlantic
This study is focused on an investigation of diapycnal diffusivity induced by internal waves breaking in the upper ocean of the subpolar North Atlantic. Turbulent diffusion plays a significant role in transferring heat and freshwater between the oceanic surface and deep ocean. The upper subpolar Nor...
| Main Author: | |
|---|---|
| Other Authors: | , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
| Published: |
Universität Bremen
2020
|
| Subjects: | |
| Online Access: | https://media.suub.uni-bremen.de/handle/elib/4574 https://doi.org/10.26092/elib/371 https://nbn-resolving.org/urn:nbn:de:gbv:46-elib45741 |
| Summary: | This study is focused on an investigation of diapycnal diffusivity induced by internal waves breaking in the upper ocean of the subpolar North Atlantic. Turbulent diffusion plays a significant role in transferring heat and freshwater between the oceanic surface and deep ocean. The upper subpolar North Atlantic is defined as a region between 40-70N and 0-65W below the seasonal thermocline. It is the complex region where mixing is induced by many processes such as double diffusion, turbulence, or isopycnal mixing. This study is an attempt to define the contribution of turbulent diapycnal mixing to the vertical transfers of heat and freshwater. To date, measurements of dissipation rate and diapycnal diffusivity are limited in the upper subpolar North Atlantic. Often, these parameters are parametrized with CTD (Conductivity-Temperature-Depth) and Lowered ADCP (Acoustic Doppler Current Profiler) data on CTD stations. Measurements of the microscale shear and temperature gradient are relatively rare in this region. Here, I added the vertical shear from the shipboard ADCP velocity data to the analysis of parametrized turbulent mixing. The main advantage of this kind of the data is that the dataset is continuous in time and space along the ship track. It helps to increase the number of estimations of diapycnal mixing in the region. I started from the description of a method for post-processing of the collected velocity datasets. After, I describe the variability of diapycnal diffusivity in the subpolar North Atlantic. The next chapter is dedicated to understanding the role of wind forcing in energy transfer to the internal waves field and turbulent mixing. The last two chapters contain results from a numerical model and investigate the role of turbulent diffusion in the vertical transfers of heat and freshwater in comparison with vertical advection, and describe the sensitivity of background stratification to changes in external forcings. Diapycnal diffusivity is used as a measure of turbulent diffusion induced by ... |
|---|