Abstract

In the Arctic Ocean, coherent low salinity anomalies, known as lenses, and often observed at the surface and are thought to result from the input of large amount of freshwater by sea ice melting and river runoff. In this study, we analyze 20 years of a simulation performed with a high resolution ocean-sea ice regional model of the Arctic to perform a systematic detection of these lenses and track their displacements in order to gain a better understanding of their life cycle. Lenses are primarily formed during summer in response to sea ice melt, river discharge, or are associated with mesoscale eddies. They are then able to survive for weeks to months, travelling long distance across the basin as their characteristic surface salinity anomalies get eroded through vertical processes. After their formation, the lenses are associated with larger sea ice melting flux during summer, and in winter sea ice formation is intensified on top of the lenses. Over the 20-year period, the number and size of the lenses have increased over the Arctic Ocean, and the formation locations have shifted following the retreat of the sea ice edge in regions such as Greenland, Barents, and Chukchi seas. Our results suggest that these localized, intermittent and coherent lenses may be important for the large scale Arctic dynamics and the ocean-sea ice interaction.