ON THE NORTH ATLANTIC SUBPOLAR GYRE VARIABILITY AS REVEALED BY ALTIMETRY AND THE OVIDE DATA SET

摘要

The meridional overturning circulation (MOC) and heat flux variability in the North Atlantic subpolar gyre were quantified from a joint analysis of hydrographic and velocity data from six repeats (1997–2010) of the Greenland-to-Portugal A25-Ovide transatlantic section, satellite altimetry and Argo. The circulation patterns obtained from ship-based observations at the A25-Ovide line revealed remarkable transport changes in the whole water column and evidenced large variations (up to 50% of the lowest value) in the MOC intensity, computed in density coordinates. The magnitudes and time scales of the MOC variability in 1993–2011 were evaluated using a MOC index built upon altimetry and Argo. The MOC index time series, validated by the good agreement with the A25-Ovide data-based estimates, exhibits a decline of ～3 Sv (1 Sv = 10~6 m~3 s~(-1)) in the MOC intensity between 1993 and 2010. The A25-Ovide data showed that the heat transport across the section is linearly related to the MOC intensity.