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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  investigations ­
  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).