Reconciling tracer and float observations of the export pathways of Labrador Sea Water

Gary, Stefan Francois, Lozier, M., Biastoch, Arne and Böning, Claus W. (2012) Reconciling tracer and float observations of the export pathways of Labrador Sea Water Geophysical Research Letters, 39 (24). L24606. DOI 10.1029/2012GL053978.

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Abstract

For more than fifty years, it has been generally accepted by oceanographers that the Deep Western Boundary Current (DWBC) is the principal conduit of recently-convected Labrador Sea Water (LSW) exported from the high-latitude North Atlantic to the equator. Supporting this supposition is observational evidence that the waters of the DWBC have consistently greater equatorward velocities, higher concentrations of passive tracers, and younger ages compared to ocean interior waters. However, recent observations and simulations of floats launched in the DWBC in the Labrador Sea show that most water parcels are quickly ejected from the DWBC and follow instead interior pathways to the subtropics. Here, we show that tracer observations from the last three decades are compatible with the existence of both DWBC and basin-interior export pathways. From analyses of observational data and model output, we find that equatorward transport in the basin interior is consistent with the large-scale vorticity balance at mid-depth. Furthermore, from the modeling analysis we show that despite higher, localized concentrations of tracer and particles in the DWBC, only 5% of particles released in the Labrador Sea are transported from the subpolar to subtropical gyre via a continuous DWBC pathway. Thus, the interior pathway is a significant contributor to LSW export.
Highlights:
- Lagrangian observations of Labrador Sea Water match Eulerian observations
- There is deep equatorward flow in the basin interior
- This interior pathway is significant compared to the pathway along the boundary

Document Type: Article
Additional Information: WOS:000312874600004
Keywords: Atlantic Meridional Overturning Circulation; Labrador Sea water; Lagrangian current measurement; deep western boundary current; intermediate depth circulation; WESTERN BOUNDARY CURRENT; NORTH-ATLANTIC OCEAN; THERMOHALINE CIRCULATION; CHLOROFLUOROCARBONS; DISTRIBUTIONS; IMPACT; EXIT; CO2
Research affiliation: OceanRep > SFB 754 > A2
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-TM Theory and Modeling
OceanRep > SFB 754
Kiel University
Refereed: Yes
DOI etc.: 10.1029/2012GL053978
ISSN: 0094-8276
Projects: SFB754
Expeditions/Models:
Date Deposited: 26 Nov 2012 07:24
Last Modified: 20 Jun 2017 07:30
URI: http://eprints.uni-kiel.de/id/eprint/19288

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