Observed deep cyclonic eddies around Southern Greenland
Zou, S., A.S. Bower, H. Furey, R.S. Pickart, L. Houpert, and N.P. Holliday, 2021. Observed deep cyclonic eddies around Southern Greenland. Journal of Physical Oceanography, 51(10), 3235-3252. https://doi.org/10.1175/JPO-D-20-0288.1
As part of the Overturning in the Subpolar North Atlantic Program, 135 acoustically-tracked RAFOS (Range And Fixing of Sound (https://www.whoi.edu/what-we-do/explore/instruments/instruments-floats-drifters/whoi-floats-drifters/rafos-float/), floats were released at depths equal to or greater than 1800 m in the subpolar North Atlantic during summers of 2014-2017. Trajectories of these floats, whose maximum lifetime is 2 years, are shown as light blue curves in the figure. They have not only illustrated the large-scale deep circulation pathways, but also revealed a number of interesting mesoscale eddy activities. Using Wavelet Ridge Analysis (Lilly and Gascard, 2006), we are able to identify potential cyclonic (counterclockwise) and anticyclonic (clockwise) rotations contained in float trajectories, which are indicated as blue and red dots, respectively. In particular, numerous cyclonic rotations were traced out by 50 deep RAFOS floats that travelled along the Deep Western Boundary Current around Greenland. Combined with hydrographic transect and moored current meter data, we find that the cyclonic rotations are associated with propagating cyclones. In general, the cyclones exhibit intensified rotation at mid-depths, with relatively swift azimuthal velocities (~30 cm/s) and small rotational radii (~10 km). Additionally, the cyclones are characterized by strong vertical density gradient in the mid-depth rotation cores and cold, fresh anomalies in the underlying deep layer. Based on the above characteristics, along with the propagating pathways revealed by float trajectories, we argue that these cyclones are likely Denmark Strait Overflow Cyclones, whose formation mechanisms are associated with the dense water descent south of the Denmark Strait. The study has been published in Journal of Physical Oceanography (Zou et al., 2021).
References Lilly, J.M. and Gascard, J.C., 2006. Wavelet ridge diagnosis of time-varying elliptical signals with application to an oceanic eddy. Nonlinear Processes in Geophysics, 13(5), pp.467-483. Zou, S., Bower, A.S., Furey, H., Pickart, R.S., Houpert, L. and Holliday, N.P., 2021.
Observed Deep Cyclonic Eddies around Southern Greenland. Journal of Physical Oceanography, 51(10), pp.3235-3252.