Analysis of Mesoscale eddies in the Lofoten Basin based on satellite altimetry

Translated by E.S. Kochetkova

We studied mesoscale eddies in the Lofoten Basin of the Norwegian Sea. The automatic eddy identification and tracking algorithm were applied to satellite altimetry. Images of 166,000 cyclonic and 169,395 anticyclonic eddies were detected in the Lofoten Basin from 1993 to 2017, then the tracking procedure was applied to them. We analyzed tracks of long-lived (lifetime more than 35 days) individual eddies. They are 120 cyclonic and 210 anticyclonic eddies. We studied a spatial distribution of mesoscale eddies in the Lofoten Basin as well as locations of their generation and dissipation. A statistical analysis of their characteristics also was carried out. We show that two predominant systems of mesoscale eddy formation exist in the Lofoten Basin. This fact may reflect two different mechanisms of eddy generation. The first one is the separation of eddies from the Norwegian current during its meandering. The second one is the direct generation of eddies inside the Lofoten Basin. There are three distinct areas of eddy generation in the frontal zone of the Norwegian current, from where eddies move to the west and north-west, forming three main trajectories. Anticyclonic eddies dominate in the area of the Lofoten vortex. Having arisen, they rotate intensively within the area of the Lofoten vortex in the anticyclonic gyre and interact obviously with the Lofoten vortex by merging. However, cyclonic eddies structures in the area of the Lofoten vortex are also found in a sufficient amount, and they are localized in the vicinity of two points with centers of 69.5° N, 4° E, and 70° N, 2.5° E. These cyclonic eddies are located in an area with cyclonic vorticity surrounding the Lofoten vortex like an annulus (shielded vortex). Mesoscale eddies that enter the area of the Lofoten vortex from outside are formed mainly in the region of the Norwegian current and tend to have the cyclonic rotation. We demonstrate that anticyclonic mesoscale eddies in the Lofoten Basin are formed mostly in the frontal zone of the Norwegian current and decay not too far from the place of their formation, while cyclonic eddies can form in different places in the Lofoten Basin. The number of eddies is much smaller in the western part of the Lofoten Basin than in other parts of it.

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