Oceanographers from St Petersburg University have obtained detailed three-dimensional structures of the mesoscale oceanic eddies in the Lofoten Basin (Nordic Seas) based on satellite data and in situ observations.The results enable scientists to highlight the significant role played by mesoscale eddies in the Arctic climate. The study is published in the Journal of Geophysical Research: Oceans.

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Oceanic eddies play a key role in ocean dynamics. Due to their ability to trap water and transport large amounts of heat and salt, eddies affect regional and global climatic processes. The main feature of the mesoscale dynamics in the Lofoten Basin is the generation of eddies from the eastern branch of the Norwegian Atlantic Slope Current and their westward propagation. These result in the eddy-induced heat and salt being transported to the central part of the basin.

The shedding of eddies from the main current also contributes to the gradual cooling of the Norwegian Atlantic Slope Current on its way to the Arctic Ocean. This, in turn, may have a significant impact on the climate of the region and, in the longer term, on the sea ice cover in the Barents Sea.

Tatyana Belonenko, project leader, Professor in the Department of Oceanology at St Petersburg University

‘Besides, mesoscale eddies provide rich feeding habitat for the local biota. Therefore, a detailed study of the mesoscale eddies in the Lofoten Basin is essential to our understanding of dynamic, climatic and biological processes in the region.’

Based on data from multiple sources – satellite altimetry, in situ data from research vessels, autonomous profiling floats, and gliders – St Petersburg University scientists together with colleagues from the University of Bergen (Norway) studied eddies in the Lofoten Basin. ‘We were able to obtain thermohaline structures of the composite cyclonic and anticyclonic eddies for the Lofoten Basin region. The composite eddy structure is a generalised image of the mesoscale eddies for the study region.’

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‘We also calculated the total heat and salt content transported by the mesoscale eddies for the whole Lofoten Basin region. The obtained data will be useful not only for climate researchers, but also for commercial fisheries,’ noted Nikita Sandalyuk, the lead author of the research paper, Assistant Lecturer in the Department of Oceanology at St Petersburg University.

He explained that mesoscale cyclonic eddies have a significant impact on the biogeochemical properties of water masses due to upwelling – a process in which deep waters rise toward the surface.

Such water masses have a high nutrient content. They are rich in nitrogen, phosphorus and silicon, which increases the biological productivity of the aquatic system. Upwelling is evident in the acquired 3D thermohaline structures of the eddies in the Lofoten Basin.

In the future, scientists plan to conduct a detailed study of the interaction between mesoscale eddies in the Lofoten Basin and their impact on the climate of the region. The research was supported by the Russian Science Foundation (project No 18-17-00027).