Analysis of a halocline mesoscale Eddy in the Northwind Basin, Arctic Ocean

Eddies have been observed at all depths and in all regions of the Arctic Ocean. However, given the complex geographic conditions and dynamic environments of this ocean, the synchronized observations of temperature, salinity, and currents, and the detailed analysis of individual eddies are still lacking in the Northwind Basin. Our study aims to address these research gaps. We observed an eddy from a mooring in the Northwind Basin in late October 2017. It is a large anticyclonic cold eddy within the Arctic halocline, with a maximum azimuthal velocity reaching 52.63 cm/s and a horizontal scale (~56 km) that significantly exceeds the first local baroclinic Rossby radius of deformation, i.e., it is in mesoscale. Its azimuthal velocity and scale are larger compared with those of nearby eddies, suggesting a relatively young state. This eddy possibly originated from the northern Chukchi Sea shelf, converging near Hanna Shoal with the Chukchi Slope Current before being advected northward into the Northwind Basin. Our study outlines detailed steps for extracting and analyzing eddies from mooring data and contributes to improving the understanding of the characteristics of Arctic Ocean eddies, providing a typical case for the investigation of eddies in the Northwind Basin.