The impact of freshwater discharges on the ocean circulation in the Skagerrak/northern North Sea area. Part II: energy analysis |
| |
| Authors: | Jon Albretsen |
| |
| Institution: | (1) Norwegian Meteorological Institute, P.O. Box 43 Blindern, 0313 Oslo, Norway |
| |
| Abstract: | We perform eddy-permitting to eddy-resolving simulations of the Skagerrak/northern North Sea with a terrain-following numerical
ocean model. We demonstrate that realistic representations of freshwater input are not required when the focus is on modelling
mesoscale structures such as meanders and eddies. To arrive at this conclusion, we analyze the results using a recently developed
energy diagnostic scheme to study the sensitivity to realistic representations of the lateral freshwater flux provided to
the area from the Baltic Sea and by the major rivers. The scheme is suitable for analysis of growth of instabilities, and
it has four basic instability processes prominent. We recognize both horizontal and vertical shear instabilities. There are
two processes where average potential energy is converted to eddy kinetic energy, and they are related to the mean gradient
in surface elevation and the mean lateral density gradient, respectively. The latter process is known as frontal instability.
We demonstrate that the change in the eddy kinetic energy field is small, despite the large variations in the hydrographic
properties from experiment to experiment. Moreover, generation of eddy activity appears at the same locations and with approximately
the same strength regardless of actual representations of freshwater input. Furthermore, we find that vertical shear instability
dominates the energy conversion processes in the Norwegian Coastal Current. Finally, we find that the areas off the northwest
coast of Denmark recognized with enhanced eddy kinetic energy level is not caused by instability processes but eddy–eddy interaction
rooted in variations in the sea level. |
| |
| Keywords: | Energy analysis Sensitivity Circulation Skagerrak |
| 本文献已被 SpringerLink 等数据库收录！ |
|
