Interannual variability of the Subpolar Mode Water properties over the Reykjanes Ridge during 1990-2006

• Published in: Journal of Geophysical Research
• Main Authors: Thierry, Virginie, De Boisseson, Eric, Mercier, Herle
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union 2008
• Subjects: North Atlantic Oscillation; subpolar mode water; North Atlantic Ocean; Greenland; Reykjanes; Iceland; North Atlantic; North Atlantic oscillation
• Online Access: https://archimer.ifremer.fr/doc/2007/publication-3487.pdf; https://doi.org/10.1029/2007JC004443; https://archimer.ifremer.fr/doc/00000/3487/

Combining hydrographic data from the OVIDE (Observatoire de la Variabilité Interannuelle à Decennale/Observatory of the Interannual to Decadal Variability) section (Greenland-Portugal) with Argo and historical CTD data over the period 1990–2006, we estimate the variability of the core properties of a variety of Subpolar Mode Water (SPMW) observed on the eastern flank of the Reykjanes Ridge. This SPMW acquires its core properties in the winter mixed layer along the eastern side of the Reykjanes Ridge. We find that the February sea surface temperature along the ridge is a proxy for its core temperature. The sources of this mode water are water masses advected by the mean cyclonic circulation in the Iceland Basin. A density compensated tendency for cooling and freshening of the SPMW core properties is observed in the early 1990s. It stops in 1996 and is followed by an increase in temperature and salinity (+1.41°C and +0.11 psu) and a decrease in density (−0.12 kg m−3) until at least 2003. During the entire period, the data do not show any significant modification in the depth of the mode water core while they suggest that the thickness of the layer shrank. The variability of the local air-sea freshwater and heat fluxes cannot explain the observed salinity and temperature variations. They are most likely related to the modifications of the properties of the SPMW sources due to the recently evidenced changes, driven by the North Atlantic Oscillation, in the relative contributions of subtropical waters and subpolar waters in the Iceland Basin.