Thermohaline structure of the Lofoten vortex in the Norwegian Sea based on in-situ and model data

Abstract

For the first time, the materials of oceanographic measurements in the Lofoten basin, made by oceanographers from the Knipovich Polar Research Institute of Marine Fisheries and Oceanography (PINRO, Murmansk, Russia) from the “Fridtjof Nansen” research ship in July 1998, 2000–2002 and 2005 during the investigations in the Norwegian and Greenland seas. We compare these materials with thermohaline sections for the same periods deriving from the MITgcm simulation. We found that the greatest horizontal contrasts of temperature and salinity are characteristic of a region with dimensions of 180–200 miles horizontally and more than 1000 m vertically, and the core of the Lofoten vortex is located in a layer at the depth of 200-800 m and has a radius varying from 20 to 60 km. It is established that apart from the quasi-permanent Lofoten vortex, many mesoscale vortices located at a depth between 50-500 m are observed in the basin, spatial scales and characteristic gradients of which can be compared to the characteristics of the Lofoten vortex. The distribution of thermohaline characteristic values according to the PINRO hydrological sections and the MITgcm model generally correspond to each other, but in the most considered cases the model data are slightly larger in zonal gradients of temperature and salinity. Based on a direct comparison of model data and field measurements, it is shown that in the considered periods the MITgcm data adequately reflect the hydrological parameters of the water area and can be used for retrospective analysis of the vortex activity in the Lofoten basin.