Unraveling the choice of the north Atlantic subpolar gyre index

Abstract The north Atlantic subpolar gyre (SPG) has been widely implicated as the source of large-scale changes in the subpolar marine environment. However, inconsistencies between indices of SPG-strength have raised questions about the active role SPG-strength and size play in determining water pro...

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Bibliographic Details
Published in:Scientific Reports
Main Authors: Koul, Vimal, Tesdal, Jan-Erik, Bersch, Manfred, Hátún, Hjálmar, Brune, Sebastian, Borchert, Leonard, Haak, Helmuth, Schrum, Corinna, Baehr, Johanna
Other Authors: Bundesministerium für Bildung und Forschung, Deutsche Forschungsgemeinschaft
Format: Article in Journal/Newspaper
Language:English
Published: Springer Science and Business Media LLC 2020
Subjects:
Multidisciplinary
North Atlantic
Online Access:http://dx.doi.org/10.1038/s41598-020-57790-5
http://www.nature.com/articles/s41598-020-57790-5.pdf
http://www.nature.com/articles/s41598-020-57790-5
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Summary:Abstract The north Atlantic subpolar gyre (SPG) has been widely implicated as the source of large-scale changes in the subpolar marine environment. However, inconsistencies between indices of SPG-strength have raised questions about the active role SPG-strength and size play in determining water properties in the eastern subpolar North Atlantic (ENA). Here, by analyzing various SPG indices derived from observations and a global coupled model, we show that the choice of the SPG index dictates the interpretation of SPG strength-salinity relationship in the ENA. Variability in geostrophic currents derived from observed hydrography and model based Lagrangian trajectories reveal zonal shifts of advective pathways in the ENA and meridional shifts in the western intergyre region. Such shifts in advective pathways are manifestations of variability in the size and strength of the SPG, and they impact salinity by modulating the proportion of subpolar and subtropical waters reaching the ENA. SPG indices based on subsurface density and principal component analysis of sea surface height variability capture these shifts in advective pathways, and are therefore best suited to describe SPG-salinity relationship in the ENA. Our results establish the dynamical constraints on the choice of the SPG index and emphasize that SPG indices should be cautiously interpreted.

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