Puzzling over the dynamics of the Lofoten Basin ‐ a sub‐Arctic hot spot of ocean variability

A sub‐Arctic “hot spot” of intense synoptic‐scale variability is observed in the Lofoten Basin (LB) of the Norwegian Sea. Using ERS‐1/2 and Envisat satellite altimetry measurements, we discover a cyclonic propagation of the synoptic‐scale sea surface height anomalies around the center of the LB. Surface drifter trajectories do not reveal an associated coherent near‐surface cyclonic flow suggesting that the propagating signals have a wavelike nature. We identify a dipole and a quadrupole wave modes rotating around the center of the LB, obtain analytic dispersion relations for these modes, and demonstrate that the observed propagation is a manifestation of topographic Rossby waves. Most of the observed waves have a wavelength of about 500 km and phase speeds ranging from 2 to 10 km/day. We show that these waves are largely responsible for the localization and amplification of sea surface height variability in the center of the LB.