'Lofoten Vortex Regeneration Through Vertical Alignment'

Marta Trodahl, University of Oslo, Geosciences, Oslo, Norway, Pål Erik Isachsen, University of Oslo, Oslo, Norway, Jonathan M Lilly, Theiss Research, La Jolla, CA, United States, Johan Nilsson, Stockholm University, Department of meteorology, Stockholm, Sweden and Nils Melsom Kristiansen, Norwegian Meteorological Institute, Ocean and Ice, Oslo, Norway
The Lofoten Basin is an important region along the route of the Norwegian Atlantic Current into the Arctic Ocean. In the Nordic Seas, the region stands out as a hot spot both in terms of mesoscale eddy activity and heat storage. The basin harbours a multitude of large, subsurface intensified anticyclones originating from the coastal current. A distinct anticyclone has been observed in the centre of the basin, the Lofoten Vortex. The vortex is a highly non-linear feature, yet extremely persistent, leaving an imprint on longterm average Sea Level Anomaly fields. This imprint strongly suggest that the vortex is a robust, long lived feature. Two main processes have been suggested for its persistence, wintertime convection and vortex mergers. However, due to the coarse spatial and temporal resolution of model data and observations used in earlier studies, a direct link to the vortex lifetime has yet to been made. We revisit the question of the vortex rejuvenation, by studying the daily vortex evolution over ten years in a high resolution model with unprecedented temporal and spatial resolution. Vortex mergers are studied in detail. We show that vertical stacking events are the main mechanism for maintaining the vortex.