There is a large number of mesoscale eddies in the Beaufort Sea, and most of them are limited to the upper 250 m, above the halocline. With the development of remote sensing, many eddies have been observed on the surface of the Arctic Ocean from SAR, Landsat, or MODIS images. Although remote sensing observations have a high horizontal resolution, the understanding of the vertical structures of eddies is still insufficient. Seismic oceanography is a recently developed ocean observation method with high resolution. This method can quickly image to full ocean depth in a few hours using low-frequency acoustic reflection imaging technology. The vertical and horizontal resolution of seismic oceanographic observation are about 10 m.

We captured the same mesoscale eddy by using two roughly perpendicular multi-channel reflection seismic profiles collected in the Northwind Basin, Arctic Ocean in late September 2011. The two seismic lines were acquired about seven days apart. The horizontal scale of the eddy is about 56 km. Vertically, the eddy extends from the near surface to ~300 m. This eddy had a core with a diameter of ∼26 km, a height of 250 m, and was surrounded by submesoscale spiral bands with large slopes. The volume of the eddy core water is about 88 km³. The horizontal current velocity, collected by the acoustic Doppler current profiler simultaneously with the seismic data, shows that the eddy had a rigid core with a rotation period of ∼26 hr, and max azimuthal velocities of 0.59 m s⁻¹. The velocity outside the core decreased in a quadratic inverse curve with the radius. During the observation, the eddy moved westward with an advection speed of ∼1 cm s⁻¹, and the net transport of the core water was about 0.05 Sv. 

Multi-arm structures can be seen in the seismic reflection data on both sides of the eddy, forming submesoscale spiral bands. These arms with large slopes, up to 4°, may be induced by eddy stirring. The core water may be Pacific warm water transported to the Northwind Basin by the Chukchi Slope Current or Beaufort Gyre This is the first application of seismic oceanography to the Arctic Ocean. Application of this method will improve understanding of the vertical structure of oceanic eddies.