EGU General Assembly 2021
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Observed Denmark Strait Overflow Cyclones around Greenland

Sijia Zou1, Amy Bower1, Heather Furey1, Robert Pickart1, Loïc Houpert2, and N. Penny Holliday2
Sijia Zou et al.
  • 1Woods Hole Oceanographic Institute, Physical Oceanography, United States of America (
  • 2National Oceanography Centre, Southampton, UK

Abundant cyclonic eddies are observed to travel along the Deep Western Boundary Current around Greenland by Lagrangian floats, hydrographic stations and moorings. Most of the cyclones have intensified rotations below the surface (700-1000 dbar), with maximum azimuthal velocities of ~30 cm/s at radii of ~10 km. The swift rotation and small radius lead to a relatively large Rossby number (~0.4), suggesting important contributions from the ageostrophic terms. The subsurface rotational core is also characterized with a local (both vertically and horizontally) potential vorticity (PV) maximum, which is associated with the pinching of isopycnals towards the mid-depths (i.e. high stratification). The PV structure suggests the origin of the cyclone as the Denmark Strait Overflow Cyclone. The latter is known to be formed by vortex stretching southwest of the Denmark Strait, where outflow waters with high PV from the sill descends the continental slope into the low PV Irminger Sea. Finally, we show that these cyclones can influence the boundary currents around Greenland by introducing property anomalies that originate from the Denmark Strait.

How to cite: Zou, S., Bower, A., Furey, H., Pickart, R., Houpert, L., and Holliday, N. P.: Observed Denmark Strait Overflow Cyclones around Greenland, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10059,, 2021.