Eddies in the Subarctic seas - on their characteristics and generation mechanism

• Main Author: Trodahl, Marta
• Format: Master Thesis
• Language: English
• Published: 2015
• Subjects: Subarctic
• Online Access: http://hdl.handle.net/10852/49170; http://urn.nb.no/URN:NBN:no-52946

The advent of satelitte observations revolutionalized Oceanography, and it has unveiled a turbulent ocean circulation dominated by mesoscale eddies (10-100km). Eddies represent an important aspect of the flow, and understanding them is essential to advance our perception of numerous ocean processes. Gaining knowledge of eddies generation mechanisms, evolution and impacts has been at the heart oceanographic research during the last decades. In this study we aim to investigate the characteristics of eddies in the Subarctic seas, and also to examine one of their generations mechanisms, baroclinic instability. Baroclinic instability has greatly aided our knowlegde of atmospheric eddies, and is also believed to the key advocator for eddies in the Ocean. We put forth the hypothesis that it can be held responsible for the large eddy acticity in th Subartctic Seas. To adress this issue we perform a linear stability analysis, that provide characteristics of the most unstable wave growing at the expense of an unstable background flow. The unstable wave’s spatial and time scales are compared to the estimates of a simpler model of baroclinic instability, the Eady model. An eddy census is conducted from a ten year model simulation. Coherent vortices are extracted from the flow and tracked in time. Characteristics such as size, vorticity, lifetimes are recorded and analyzed. The scales of the linear waves and nonlinearly evolving eddies from the detection scheme are then compared. We did not anticipate that local baroclinic instability can account for all aspects of a fully turbulent field, but we traced its activity in the initial stages of the generation process.