Observed deep cyclonic eddies around Southern Greenland

Thumbnail Image
Date
2021-10-01
Authors
Zou, Sijia
Bower, Amy S.
Furey, Heather H.
Pickart, Robert S.
Houpert, Loïc
Holliday, Naomi Penny
Alternative Title
Date Created
Location
DOI
10.1175/JPO-D-20-0288.1
Related Materials
Replaces
Replaced By
Keywords
North Atlantic Ocean
Cyclogenesis/cyclolysis
Lagrangian circulation/transport
Mesoscale processes
Ocean circulation
Abstract
Recent mooring measurements from the Overturning in the Subpolar North Atlantic Program have revealed abundant cyclonic eddies at both sides of Cape Farewell, the southern tip of Greenland. In this study, we present further observational evidence, from both Eulerian and Lagrangian perspectives, of deep cyclonic eddies with intense rotation (ζ/f > 1) around southern Greenland and into the Labrador Sea. Most of the observed cyclones exhibit strongest rotation below the surface at 700–1000 dbar, where maximum azimuthal velocities are ~30 cm s−1 at radii of ~10 km, with rotational periods of 2–3 days. The cyclonic rotation can extend to the deep overflow water layer (below 1800 dbar), albeit with weaker azimuthal velocities (~10 cm s−1) and longer rotational periods of about one week. Within the middepth rotation cores, the cyclones are in near solid-body rotation and have the potential to trap and transport water. The first high-resolution hydrographic transect across such a cyclone indicates that it is characterized by a local (both vertically and horizontally) potential vorticity maximum in its middepth core and cold, fresh anomalies in the deep overflow water layer, suggesting its source as the Denmark Strait outflow. Additionally, the propagation and evolution of the cyclonic eddies are illustrated with deep Lagrangian floats, including their detachments from the boundary currents to the basin interior. Taken together, the combined Eulerian and Lagrangian observations have provided new insights on the boundary current variability and boundary–interior exchange over a geographically large scale near southern Greenland, calling for further investigations on the (sub)mesoscale dynamics in the region.
Description
Author Posting. © American Meteorological Society, 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 51(10), (2021): 3235–3252, https://doi.org/10.1175/JPO-D-20-0288.1.
Embargo Date
Citation
Zou, S., Bower, A. S., Furey, H., Pickart, R. S., Houpert, L., & Holliday, N. P. (2021). Observed deep cyclonic eddies around Southern Greenland. Journal of Physical Oceanography, 51(10), 3235–3252.
Cruises
Cruise ID
Cruise DOI
Vessel Name