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Inferring Advective Timescales and Overturning Pathways of the Deep Western Boundary Current in the North Atlantic through Labrador Sea Water Advection
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  • Leah N Chomiak,
  • Igor Yashayaev,
  • Denis L. Volkov,
  • Claudia Schmid,
  • James Albert Hooper
Leah N Chomiak
University of Miami - RSMAS / NOAA AOML

Corresponding Author:leah.chomiak@rsmas.miami.edu

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Igor Yashayaev
Bedford Institute of Oceanography, Fisheries and Oceans Canada, Dartmouth, NS, Canada
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Denis L. Volkov
University of Miami / AOML
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Claudia Schmid
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James Albert Hooper
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The Subpolar North Atlantic plays a critical role in the formation of the deep water masses which drive Atlantic Meridional Overturning Circulation (AMOC). Labrador Sea Water (LSW) is formed in the Labrador Sea and exported predominantly via the Deep Western Boundary Current (DWBC). The DWBC is an essential component of the AMOC advecting deep waters southward, flowing at depth along the continental slope of the western Atlantic. By combining sustained hydrographic observations from the Labrador Sea, Line W, Bermuda basin, and offshore of Abaco Island along 26.5°N, we investigate the signal propagation and advective timescales of LSW via the DWBC from its source region to the Tropical Atlantic through various approaches using robust neutral density classifications. Two individually-defined LSW classes are observed to advect on timescales that support a new plausible hydrographically-observed advective pathway. We find each LSW class to advect on independent timescales, and validate a hypothesized alternative-interior advection pathway branching from the DWBC by observing LSW outside of the DWBC in the Bermuda basin just prior to or on the same timescale as at 26.5°N- 10-15 years after leaving the source region. Advective timescales estimated herein indicate that this interior pathway is likely the main advective pathway; it remains uncertain whether a direct pathway plays a significant advective role. Using LSW convective signals as advective tracers along the DWBC permits the estimation of advective timescales from the subpolar to tropical latitudes, illuminating deep water advection pathways across the North Atlantic and the lower-limb of AMOC as a whole.