26 
Sy, A. et al. (2002): Upper Ocean Climate Shlp-ot-Opportunity Programme of BSH - A Status Report 
NAO-lndex 
Relationship between NAO-index and 
volume transports from Fig. 16 (top) after 
transport time series has been time 
shifted by - 5 years and use of second 
order polynomial least squares fitting. 
NAOi time series smoothed by running 
mean filter q = 3. Although the ocean 
volume transports can be linked with time 
lag of 5 years to the atmosphere winter 
NAO (DJF) at an explained variance of 
62 % the assigned cause and effect 
cannot yet be decided. 
Left: Comparison of correlation results of 
linear and second order fitting for 
different phase lags. 
Fig, 17: 
Phase [Years] 
Various observations have shown a pronounced surface and subsurface temperature variability 
on a multi-year time scale in the subtropical and mid-latitude North Atlantic (e.g. Hansen and 
Bezdek, 1996; Sutton and Allen, 1997; Molinari et al., 1997; Yang, 1999; Krahmann et al., 
2001). Our analysis of XBT data shows similar results of temporal and spatial variability for the 
entire main thermocline (Figs. 14, 18, 19, 21). 
As one of the most striking features, the 13-year time series of upper ocean heat content 
anomalies along AX-3 shows fluctuations on inter-annual time scales with periods of about 
5 years (Fig. 18 top, 19). The observed periodicity coincides with results of earlier investi 
gations of the subtropical Atlantic Ocean (Molinari et al., 1997). Again, the question as to the 
controlling mechanism is still open. We found no evidence of a direct relation with the warming 
of the Subpolar Mode Water as observed by Bersch et al. (1999) or of a slow anomalous SST 
pattern propagation as suggested by Sutten and Allen (1997).