Lofoten Vortex

[3] Due to the presence of the permanent vortex, the Lofoten basin features a localised area with high levels of sea surface temperature and eddy kinetic energy.

The local currents inside the vortex and the strong convection observed during winter generate a hot spot rich in nutrients, affecting the surrounding marine biology.

The estimated radius of the vortex is 15–20 km and presents a 1200 m thick core of Atlantic Water (warm and saline) swirling at velocities that reach 0.8 m/s at 600–800 m depth.

[4] Strong seasonality characterises the density profile of the vortex: during summer a double core structure is detectable, with a shallow pycnocline created by the stratification of surface water heated by the sun.

On the other hand, in winter the surface's cooling creates strong convection that homogenises the density profile and deepens the pycnocline up to 1200 m depth.

[12] Likewise, the anticyclones released from the Norwegian Atlantic Slope Current (NwASC) spiral counterclockwise towards the deepest part of the Lofoten Basin.

[9] Some of the anticyclones terminate within the basin, whilst the longer-lasting trajectories (of 3–6 months) are traced back to the slope region related to the elevated eddy kinetic energy.

[10][4] During a merging event, a vertical alignment between the light core anticyclones and the denser Lofoten Vortex occurs, creating a double-core.

This results in formation of a localised, vertically homogeneous, positive thermohaline anomaly in the intermediate and upper parts of the deep layer.

The increase in the thermohaline anomaly in winter and spring is accompanied by the deepening and shrinking of the vortex to the Rossby radius of deformation of about 10 km.

Most of the dense water production in the Nordic Seas takes place on the east side of the Mohn Ridge system, in the Lofoten Basin.

Mean eddy kinetic energy (EKE) profile in the Lofoten basin during July 2000. The red arrows represent the mean geostrophic currents during the same month. [ 1 ] [ 2 ]
Bathymetry of the Nordic Seas, with iso depth contours and description of the main topographic features of the area. [ 5 ]
Mean sea level anomaly (SLA) in the Lofoten Basin during July 2000, with the mean currents also displayed as a quiver plot.The Lofoten Vortex is detectable as a bright spot of positive relative SLA between 3-5°E and 70°N, surrounded by anticyclonic swirling arrows. [ 1 ] [ 2 ]
Nordic Seas bathymetry [ 11 ] and main currents. The NwAC is shown splitting in the NwAFC and NwASC. An approximate location of the Lofoten vortex is also marked.