On the currents and transports connected with the Atlantic meridional overturning circulation in the subpolar North Atlantic

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Xu, X., Hurlburt, H. E., Schmitz Jr., W. J., Zantopp, Rainer, Fischer, J., Hogan, P. J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union 2013
• Subjects: currents; meridional; north atlantic; subpolar; Labrador Sea; North Atlantic; North Atlantic oscillation
• Online Access: https://hdl.handle.net/1969.6/90324; https://doi.org/10.1002/jgrc.20065

Results from an interannually forced, 0.08° eddy-resolving simulation based on the Hybrid Coordinate Ocean Model, in conjunction with a small but well-determined transport database, are used to investigate the currents and transports associated with the Atlantic meridional overturning circulation (AMOC) in the subpolar North Atlantic (SPNA). The model results yield a consistent warming in the western SPNA since the early 1990s, along with mean transports similar to those observed for the trans-basin AMOC across the World Ocean Circulation Experiment hydrographic section AR19 (16.4 Sv) and boundary currents at the exit of the Labrador Sea near 53°N (39.0 Sv) and east of the Grand Banks near 43°N (15.9 Sv). Over a 34 year integration, the model-determined AMOC across the AR19 section and the western boundary current near 53°N both exhibit no systematic trend but some long-term (interannual and longer) variabilities, including a decadal transport variation of 3–4 Sv from relatively high in the 1990s to low in the 2000s. The decadal variability of the model boundary current transport near 53°N lags the observed winter time North Atlantic Oscillation index by about 2 years and leads the model AMOC across the AR19 section by about 1 year. The model results also show that the long-term variabilities are low compared to those on shorter time scales. Thus, rapid sampling of the current over long time intervals is required to filter out high-frequency variabilities in order to determine the lower frequency variabilities of interest. This work is a contribution to the project U.S.-GODAE: Global ocean prediction using the HYbrid Coordinate Ocean Model, funded under the National Ocean Partnership Program, and to the projects Global remote littoral forcing via deep water pathways (program element 601153N) and Full column mixing for numerical ocean models (602435N), funded by the Office of Naval Research. The moored current meter observations are supported by the German Research ministry contract 03F0605B and by the EU FP7 ...