Abstract
The Marginal Ice Zone (MIZ) is a dynamic region where the atmosphere, ocean, and sea ice actively interact, giving rise to frequent eddy formation. Clarifying the processes governing this zone is crucial for both accurate modeling of local circulation and improved prediction of Arctic climate change, particularly sea-ice retreat and ecosystem shifts. This study investigates a mesoscale eddy in the poorly studied northeastern Kara Sea MIZ using a joint analysis of in situ and satellite measurements from summer 2024. We also apply principles from ellipsoidal vortex theory. The eddy's complex evolution is described, and its key parameters are quantified. The eddy was found to contain and transport a substantial volume of freshened cold water, potentially modifying the structure of surrounding waters. Two potential mechanisms for the eddy's formation were proposed, each requiring further investigation through dedicated modeling and observational efforts. Significant differences in the phytoplankton biomass and production rates were identified across the eddy, whereas species composition showed no significant variation. These results highlight the role of mesoscale eddies in freshwater redistribution and biophysical coupling in the MIZ, while underscoring the need to advance theories of eddy dynamics and incorporate these processes into regional and climate models.