My last lecture was on satellite observations of oceanic eddies. Eddies are regions of rotating water, surrounded by non-rotating water. Eddies of different spatial scales evolve into the movement of great amounts of water, and therefore play an important role in the redistribution of pollutants and the delivery of nutrients for phytoplankton.
First we looked through some satellite imagery showing various manifestations of eddies. In thermal imagery, eddies can be seen due to differences in sea surface temperature between the inside and outside of the eddies. In visible imagery, eddies are visualized by suspended particles in the water, which serve as passive tracers of their formation. In radar imagery, it is either surfactant films or enhanced signal backscattering on shear currents which make eddies visible.
Then, general ideas of eddy generation were discussed. Eddies can appear either due to velocity and density gradients in the water (in the photo I am demonstrating a gradient with my arms) or by applying a direct action. Among the most important physical reasons of eddy formation are friction caused by a coastline, fronts (borders between waters with different characteristics), variations in the coastline and bottom topography, and obstacles (like islands).
Finally I presented some results of my own research. I have studied mesoscale eddies (with a diameter of several tens of kilometers) and submesoscale eddies (up to about 20 km) in the Baltic, Black, Caspian, Red, and Mediterranean seas. Within this study I had to visually analyze about 10,000 images of different types and I manually detected about 20,000 eddies. As a result of this hard job, for the first time the areas of the most frequent eddy observations were defined, and the statistical parameters of eddy spatial scale were retrieved.
I think that in general the lecture was interesting. Now I can be more relaxed and spend more time enjoying the severe Arctic weather outside.
- Svetlana Karimova