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Ocean Science An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/os-2018-56
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
14 May 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Ocean Science (OS).
Mean circulation and EKE distribution in the Labrador Sea Water level of the subpolar North Atlantic
Jürgen Fischer, Johannes Karstensen, Marilena Oltmanns, and Sunke Schmidtko GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24115 Kiel
Abstract. A long term mean flow field for the subpolar North Atlantic region with a horizontal resolution of approximately 25 km is created by gridding Argo-derived velocity vectors using two different topography following interpolation schemes. The 10-d float displacements in the typical drift depths of 1000 m to 1500 m represent the flow in the Labrador Sea Water density range. Both mapping algorithms separate the flow field into potential vorticity (PV) conserving, i.e. topography following contribution and a deviating part, which we define as the eddy contribution. To verify the significance of the separation, we compare the mean flow and the eddy kinetic energy (EKE), derived from both mapping algorithms, with those obtained from multiyear mooring observations.

The PV-conserving mean flow is characterized by stable boundary currents along all major topographic features including shelf breaks and basin-interior topographic ridges such as the Reykjanes Ridge or the Rockall Plateau. Mid-basin northward advection pathways from the northeastern Labrador Sea into the Irminger Sea and from the Mid Atlantic Ridge region into the Iceland basin are well-resolved. An eastward flow is present across the southern boundary of the subpolar gyre near 52° N, the latitude of the Charlie Gibbs Fracture Zone.

The mid-depth EKE field resembles most of the satellite-derived surface EKE field. However, noticeable differences exist along the northward advection pathways in the Irminger Sea and the Iceland basin, where the deep EKE exceeds the surface EKE field. Further, the ratio between mean flow and the square root of the EKE, the Peclet Number, reveals distinct advection-dominated regions as well as basin interior regimes in which mixing is prevailing.

Citation: Fischer, J., Karstensen, J., Oltmanns, M., and Schmidtko, S.: Mean circulation and EKE distribution in the Labrador Sea Water level of the subpolar North Atlantic, Ocean Sci. Discuss., https://doi.org/10.5194/os-2018-56, in review, 2018.
Jürgen Fischer et al.
Jürgen Fischer et al.
Jürgen Fischer et al.

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Short summary
Based on nearly 17 years of profiling (Argo) float data, high resolution (~ 25 km grid) maps of mean flow and eddy kinetic energy (EKE) were constructed for the intermediate-deep subpolar North Atlantic. Robust boundary currents along topographic slopes, mid-basin advective pathways and stagnation regimes were identified. The ration of mean flow vs. the square root of EKE indicates regions dominated by advection, and large regions in which eddy diffusion prevails.
Based on nearly 17 years of profiling (Argo) float data, high resolution (~ 25 km grid) maps of...
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