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Transport Variability of the Irminger Sea Deep Western Boundary Current From a Mooring Array
Author(s) -
Hopkins J. E.,
Holliday N. P.,
Rayner D.,
Houpert L.,
Le Bras I.,
Straneo F.,
Wilson C.,
Bacon S.
Publication year - 2019
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1029/2018jc014730
Subject(s) - mooring , boundary current , oceanography , rossby wave , geology , current (fluid) , zonal and meridional , eddy , sea surface height , deep sea , latitude , deep water , climatology , continental shelf , water mass , dynamic height , ekman transport , ocean current , hydrography , sea surface temperature , geography , geodesy , meteorology , upwelling , turbulence
The Deep Western Boundary Current in the subpolar North Atlantic is the lower limb of the Atlantic Meridional Overturning Circulation and a key component of the global climate system. Here, a mooring array deployed at 60°N in the Irminger Sea, between 2014 and 2016, provides the longest continuous record of total Deep Western Boundary Current volume transport at this latitude. The 1.8‐year averaged transport of water denser than σ θ = 27.8 kg/m 3 was −10.8 ± 4.9 Sv (mean ± 1 std; 1 Sv = 10 6 m 3 /s). Of this total, we find −4.1 ± 1.4 Sv within the densest layer ( σ θ > 27.88 kg/m 3 ) that originated from the Denmark Strait Overflow. The lighter North East Atlantic Deep Water layer ( σ θ = 27.8–27.88 kg/m 3 ) carries −6.5 ± 7.7 Sv. The variability in transport ranges between 2 and 65 days. There is a distinct shift from high to low frequency with distance from the East Greenland slope. High‐frequency fluctuations (2–8 days) close to the continental slope are likely associated with topographic Rossby waves and/or cyclonic eddies. Here, perturbations in layer thickness make a significant (20–60%) contribution to transport variability. In deeper water, toward the center of the Irminger Basin, transport variance at 55 days dominates. Our results suggest that there has been a 1.8 Sv increase in total transport since 2005–2006, but this difference can be accounted for by a range of methodological and data limitation biases.